Chart 1 shows we are still carbonising, and chart 2 shows the seperate emissions sources.
Chart 3 shows that ‘every year energy use increases, & most of the increases come from fossil fuels.’3
In the absence of policies global warming is expected, to reach 4.1°C – 4.8°C above pre-industrial by the end of the century. The emissions that drive this warming are often called Baseline scenarios (‘Baselines’ in the above figure) and are taken from the IPCC AR5 Working Group III. Current policies presently in place around the world are projected to reduce baseline emissions and result in about 3.3°C warming above pre-industrial levels. The unconditional pledges and targets that governments have made, including NDCs as of December 2018, would limit warming to about 3.0°C above pre-industrial levels, or in probabilistic terms, likely (66% or greater chance) limit warming below 3.2°C. This result is similar to our estimate last year, reflecting the fact that little has changed in terms of government commitments and targets in the past 12 months.
2100 warming projections, Climate Action Tracker, accessed Feb 2019. 6 Note that NDCs are “Nationally Determined Contributions” and detail the supposed intention of each country to reduce its emissions.7
Clearly, for any chance of avoiding evermore severe and frequent climate impacts, and the collapse of civilisation, not only must rapid decarbonisation begin immediately on a global scale, but also massive government investment in research and development of CDR. Current capitalist economic priorities and fossil fuel extraction must cease.
Humanity’s CO2 emissions: (i) are currently trapping two thirds of the energy causing global warming, (ii) are the only rapidly increasing contributor, (iii) almost solely determine our long term warming commitment, and (iv) continue to grow with no peak in sight. Half of all CO2 ever emitted has been emitted recently and almost all by the world’s energy system.
Global Carbon Project. (2019). Supplemental data of Global Carbon Budget 2019 (Version 1.0) [Data set]. Global Carbon Project, https://www.icos-cp.eu/GCP/2019, download labelled ‘2019 Global Budget v1.0’.(↩)(↩)
Dr Hansen has published many studies, in conjunction with other scientists about climate change.1
Dr. James Hansen, formerly Director of the NASA Goddard Institute for Space Studies, is an Adjunct Professor at Columbia University’s Earth Institute, where he directs a program in Climate Science, Awareness and Solutions. Dr. Hansen is best known for his testimony on climate change to congressional committees in the 1980s that helped raise broad awareness of the global warming issue. He was elected to the National Academy of Sciences in 1995 and was designated by Time Magazine in 2006 as one of the 100 most influential people on Earth. He has received numerous awards including the Carl-Gustaf Rossby and Roger Revelle Research Medals, the Sophie Prize and the Blue Planet Prize. Dr. Hansen is recognized for speaking truth to power, for identifying ineffectual policies as greenwash, and for outlining actions that the public must take to protect the future of young people and other life on our planet.
Hansen makes the point that 1.5℃ is not safe because it’s warmer than anytime of the Holocene, and as warm as the Eemian when seas were 6–9m higher. Instead, Hansen prescribes changes needed to reduce atmospheric CO2 to less than 350 ppm, in order to limit global temperature close to the Holocene range.
Dutton et al. (2015) conclude that the best estimate for Eemian temperature is +1℃ relative to preindustrial. Consistent with these estimates and the discussion of Masson-Delmotte et al. (2013), we assume that maximum Eemian temperature was +1℃ relative to preindustrial with an uncertainty of at least 0.5℃.
These considerations raise the question of whether 2℃, or even 1.5℃, is an appropriate target to protect the well-being of young people and future generations. Indeed, Hansen et al. (2008) concluded that “if humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, …CO2 will need to be reduced… to at most 350 ppm, but likely less than that”, and further “if the present overshoot of the target CO2 is not brief, there is a possibility of seeding irreversible catastrophic effects”.
A danger of 1.5 or 2℃ targets is that they are far above the Holocene temperature range. If such temperature levels are allowed to long exist they will spur “slow” amplifying feed-backs (Hansen et al., 2013b; Rohling et al., 2013; Masson-Delmotte et al., 2013), which have potential to run out of humanity’s control. The most threatening slow feedback likely is ice sheet melt and consequent significant sea level rise, as occurred in the Eemian, but there are other risks in pushing the climate system far out of its Holocene range. Methane release from thawing permafrost and methane hydrates is another potential feedback, for example, but the magnitude and timescale of this is unclear (O’Connor et al., 2010; Quiquet et al., 2015).
Here we examine the fossil fuel emission reductions required to restore atmospheric CO2 to 350 ppm or less, so as to keep global temperature close to the Holocene range, in addition to the canonical 1.5 and 2℃ targets.
Hansen et al., 2017, Young people’s burden: requirement of negative CO2 emissions5
Chart 2 shows a range of pathways, and three in (b) return global surface temperature to within our range of uncertainty about the Holocene maximum (0.5℃ to 0.75℃).
Note the units for CO2 extraction (i.e. CDR) above are of units peta-grams of carbon (PgC). This is equivalent to billions of tons of carbon (GtC). To compare these quantities with those from the previous section, and so convert GtC to GtCO2, they must be multiplied by 44/12 (the ratio of the molecular weight of CO2 to C).
The green pathway shown demands 869GtCO2 and a CO2 reduction rate of -3%/yr (i.e. CO2 emissions in 2030 reduced to two thirds of 2020 level). This is very similar to the IPCC’s pathway 1.5°C-with-low-overshoot that prescribes an annual CO2 reduction rate of -4.5%/yr and CDR of about 800 GtCO2, but Hansen & Co state the global surface temperature in 2100 would lower, to less than +1°C.
The blue pathway is more precautionary by relying more on CO2 reduction (-6%/yr) and less on CDR (153PgC or 561 GtCO2). This quantity of CDR still demands an annual quantity of CDR removal about the size of the global ocean by 2100. This now seems an inescapable requirement.
Hansen, J., Sato, M., Kharecha, P., von Schuckmann, K., Beerling, D. J., Cao, J., Marcott, S., Masson-Delmotte, V., Prather, M. J., Rohling, E. J., Shakun, J., Smith, P., Lacis, A., Russell, G., and Ruedy, R.: Young people’s burden: requirement of negative CO2 emissions, Earth Syst. Dynam., 8, 577-616, https://doi.org/10.5194/esd-8-577-2017, 2017. https://www.earth-syst-dynam.net/8/577/2017/(↩)
Hansen, J., Sato, M., Kharecha, P., von Schuckmann, K., Beerling, D. J., Cao, J., Marcott, S., Masson-Delmotte, V., Prather, M. J., Rohling, E. J., Shakun, J., Smith, P., Lacis, A., Russell, G., and Ruedy, R.: Young people’s burden: requirement of negative CO2 emissions, Earth Syst. Dynam., 8, 577-616, https://doi.org/10.5194/esd-8-577-2017, 2017.(↩)
To hold global average temperature steady, emissions need to reach ‘net zero’. Net zero emissions are achieved when emissions of greenhouse gases to the atmosphere are balanced by anthropogenic removals.
An increase in global average temperature of e.g. 1.5°C corresponds to a limited net amount of CO2 being emitted. This amount of CO2 is usually referred to as the carbon budget for 1.5°C.
The rate at which CO2 will be emitted determines how many years remain until emissions must reach ‘net-zero’.
Limiting warming to 1.5°C or 2°C without overspending the corresponding carbon budget would require very fast changes in electricity production, transport, construction, agriculture and industry.
IPCC. 2018. Understanding the IPCC Special Report on 1.5°C.1
Net zero emissions requires both rapid emission reductions (also known as decarbonisation), AND anthropogenic removals (also known as “negative emission technologies” (NETs) or “carbon dioxide removal” (CDR)). Both are now required because: (i) civilisation has left the task of decarbonisation recklessly late; (ii) there is a limit to the maximum rate of decarbonisation that civilisation can manage; and (iii) there is a limit to the minimum level of annual emissions that civilisation can manage (also known as a “carbon-floor”, that must be perpetually offset).
A typical future idealistic future CO2 emission scenario is shown below.
The IPCC’s Special Report on 1.5°C presents the six future emission categories (or pathway groups) shown below (note the worryingly small probabilities of success associated with each).
For each of the pathways above, there are corresponding prescribed future rates of decarbonisation and associated increasing CDR. Placing CDR aside for the moment, it’s useful to consider historic examples of decarbonisation. There have been three notable examples: France and Sweden in the 1980s due to an increased supply of nuclear energy, and Russia in the 1990s after the collapse of the Soviet Union.
As shown below, the decarbonisation in France occurred between 1979 and 1988, and at a rate equivalent to a linear decline of -3.25%/yr of the initial level of emissions in 1979. Sweden managed -5.6%/yr3 and Russia endured -5.9%.
Prescribed decarbonisation rates for the next decade can be calculated using the table below and compared to the historic reductions above.
The level of CO2 from fossil fuels and industry (net) in 2019 was 36.8GtCO2.6 Under the assumption that the prescribed decarbonisation for the future pathway 1.5°C-with-low-overshoot begins in 2021, and that emissions in 2020 equal those in 2019, then CO2 emissions from fossil fuels and industry would need to decline from 36.8GtCO2 to 20.6GtCO2 in a decade (refer to the table above). This is equivalent to an annual linear decline of -4.4% of the original amount each year, as calculated below.
While this rate of decarbonisation is similar to that which occurred in France, Sweden and Russia, the scale of these examples should be considered: During their respective decarbonisation, France was responsible for 2.1% of global CO2 emissions,8 Sweden 0.4%9 and Russia 9%.10 The decarbonisation that occurred in Russia is the only example that was significant at rate and scale, but this caused hardship, riots, massacres and even a decline in the life expectancy of males from 65 down to 58 years.11 A global decarbonisation at any rate for a decade is without historic precedent. Alternatively, the pathway 1.5°C-with-high-overshoot, that has a median warming of +1.7˚C and a 20% chance of exceeding +2°C12 demands a global decarbonisation rate to 2030 of -2.7%/yr. This rate would need to be enacted in 2021, despite civilisation having carbonised at about this rate since year 2000, as shown below, effectively somehow being an emissions-backflip.12
Even the pathway Higher-2°C, that has 40% chance of exceeding 2°C, and a 13% chance of exceeding 2.5°C as early as 207512 requires immediate decarbonisation at a rate of -1.6%/yr.
Therefore even the rapid and drastic decarbonisation shown in Chart 5 above, along with the prescribed concurrent CDR detailed further below, leaves us with a 40% chance of warming the planet to a temperature that hasn’t occurred for around 3–5 million years.13
In the mid-Pliocene, 3–5 million years ago, the last time that the Earth’s atmosphere contained 400ppm of CO2, global mean surface temperature was 2–3℃ warmer than today, the Greenland and West Antarctic ice sheets melted and even some of the East Antarctic ice was lost, leading to sea levels that were 10–20m higher than they are today.
Decarbonisation is only “half the story”. Pathways to limit warming become more challenging once the prescribed scale and rate of concurrent carbon dioxide removal (CDR) is considered. The CDR required for pathways Below-1.5°C and 1.5°C-with-low-overshoot is shown in Chart 6; (a) shows the annual quantity of CDR to be removed each year, and (b) the cumulative quantity over time.
640–950 GtCO2 removal is required for a likely chance of limiting end-of-century warming to 1.5 °C. In the absence of strengthened pre-2030 pledges, long-term CO2 commitments are increased by 160–330 GtCO2, further jeopardizing achievement of the 1.5 °C goal and increasing dependence on CO2 removal.
Residual fossil CO2 emissions in 1.5–2 °C pathways.16
The scale of the decarbonisation challenge to meet the Paris Agreement is underplayed in the public arena.It will require precipitous emissions reductions within 40 years and a new carbon sink on the scale of the ocean sink. Even then, the world is extremely likely to overshoot. A catastrophic failure of policy, for example, waiting another decade for transformative policy and full commitments to fossil-free economies, will have irreversible and deleterious repercussions for humanity’s remaining time on Earth. Only a global zero carbon roadmap will put the world on a course to phase-out greenhouse gas emissions and create the essential carbon sinks for Earth-system stability, without which, world prosperity is not possible.
Rockström, J. et al. (2016), The world’s biggest gamble.17
As shown below, the global ocean absorbed about 9GtCO2/yr of anthropogenic emissions over the last decade, and the land carbon sink about 12GtCO2/yr. (Interestingly, also shown is the carbon budget imbalance of 2GtCO2/yr; this is a gap in our understanding as stated in figure 7 and amounts to about 5% of our total emissions).18 Therefore, the quantity of annual CDR by 2050, prescribed for the pathways Below-1.5°C and 1.5°C-with-low-overshoot, is equivalent to an additional carbon sink of the size of a global ocean. By 2100 this is just under 1.7 global oceans, as shown by the right hand axis of Chart 10(a) above.
CDR deployed at scale is unproven, and reliance on such technology is a major risk in the ability to limit warming to 1.5°C.
Approaches under consideration include the enhancement of terrestrial and coastal carbon storage in plants and soils such as afforestation and reforestation, soil carbon enhancement, and other conservation, restoration, and management options for natural and managed land and coastal ecosystems. Biochar sequestration provides an additional route for terrestrial carbon storage. Other approaches are concerned with storing atmospheric carbon dioxide in geological formations. They include the combination of biomass use for energy production with carbon capture and storage (BECCS) and direct air capture with storage (DACCS) using chemical solvents and sorbents. Further approaches investigate the mineralization of atmospheric carbon dioxide, including enhanced weathering of rocks. A fourth group of approaches is concerned with the sequestration of carbon dioxide in the oceans, for example by means of ocean alkalinization. The costs, CDR potential and environmental side effects of several of these measures are increasingly investigated and compared in the literature, but large uncertainties remain, in particular concerning the feasibility and impact of large-scale deployment of CDR measures.
Note that carbon capture and storage (CCS) is not a form of CDR because it does not remove CO2 from the atmosphere; instead its aim, should it ever come to fruition, is to lower the emission of CO2 from fossil fuelled energy generation, allowing it to be produced without an impact on the remaining carbon budget.
A variety of pilot projects failed in the past. One was a joint effort by one of the largest U.S. utilities, American Electric Power, and the Energy Department22 to capture 15 percent of emissions from coal-fired power plants. It closed down after two years. Another carbon capture project attached to a new coal-fired power plant in Mississippi ran into so many technical problems and billions of dollars in cost overruns that after six years its owners abandoned the carbon capture project and converted the plant to burn natural gas for power generation.
Dec 2018, The Washington Post, ‘Carbon removal is now a thing’: Radical fixes get a boost at climate talks.23
Our long-term warming commitment is determined by the quantity of long-lived greenhouse gasses emitted. Therefore the specific warming limits of 1.5˚C and 2˚C have corresponding carbon budgets, expressed in quantities of tonnes of CO2. The IPCC budgets include forcings (i.e. warming contributions) from nonCO2 gases in their range of budget uncertainties.
The size of the remaining budgets are extremely small relative to our annual emissions, suggesting that technological change has a limited role in the short term. Social change is also required, such as carbon pricing and or rationing of carbon.
The remaining carbon budget from 2018 onwards is 580GtCO2 for a 50% chance of keeping warming below 1.5C. This is less than 15 years of global emissions at current rates.24
So, what does that mean?
This means that if we start reducing emissions steeply now and by the time we reach net-zero levels we have not emitted more than 580GtCO2, our best scientific understanding tells us have we expect a one-in-two chance that warming would be kept to 1.5C.
Moreover, if we want to be sure that this is also true until the end of the century, we’d have to aim to emit only 480GtCO2 until we reach net-zero instead. This is under 12 years of current emissions.
‘A new approach for understanding the remaining carbon budget’, Dr Joeri Rogelj, Prof Piers Forster, CarbonBrief 2019.25
The remaining carbon budgets from 2020 onwards are listed below in table 3, calculated by subtracting the annual emissions of years 2018 and 2019 (shown in the supporting tables), away from the IPCC’s budgets shown in table 3. Also shown are the same remaining budgets with 50% of total uncertainties applied in either direction (50% was chosen because it would be unlikely for all uncertainties to align at an extremity). Note that 50th percentile of climate sensitivity refers to the most likely value.
Table 1 shows the IPCC’s remaining carbon budget for 1.5˚C may be spent in 12 years at the current rate of emissions, but if 50% of total uncertainties are applied in either direction, the same budget is spent sometime in the next 2 to 23 years. The usefulness of IPCC budgets is questionable because associated with each budget are very large uncertainties and warming that will trigger rapid and large sea level rise. The exceedance of any budget doesn’t herald the end of our chance to limit and reduce warming. Instead it should be a very loud alarm that reminds us our greenhouse gas emissions remain dangerously excessive and unmanaged.
In summary, the IPCC’s pathway 1.5°C-with-low-overshoot prescribes the world decarbonise at a rate 1.6 times faster than it has recently carbonised (-4.4%/2.5%), and carbon dioxide removal (CDR) on the scale of the global ocean operational by 2050, and 1.7 oceans by 2100. In year 2100, this pathway has a 28% chance of exceeding 1.5°C, and a 7% chance of exceeding 2°C.26
p. 100, Table 2.1, IPCC, 2018: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press. https://www.ipcc.ch/sr15/download/(↩)
p. 119, Table 2.4, IPCC, 2018: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press. https://www.ipcc.ch/sr15/download/(↩)
Global Carbon Project. (2019). Supplemental data of Global Carbon Budget 2019 (Version 1.0) [Data set]. Global Carbon Project, https://www.icos-cp.eu/GCP/2019, download labelled ‘2019 Global Budget v1.0’.(↩)(↩)(↩)
Calculated using prescribed levels of annual CDR addition shown in p. 128, fig 2.13, IPCC, 2018: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press.https://www.ipcc.ch/sr15/download/(↩)
p. 96, IPCC, 2018: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press. https://www.ipcc.ch/sr15/download/(↩)
p. 121, IPCC, 2018: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press. https://www.ipcc.ch/sr15/download/(↩)
p. 108, table 2.2, IPCC, 2018: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press. https://www.ipcc.ch/sr15/(↩)
The United Nations Framework Convention on Climate Change (UNFCCC) is a treaty with the objective of: “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.”4 This is informed by the Intergovernmental Panel on Climate Change (IPCC), within which “experts review and synthesize available scientific and technical knowledge.”5 The IPCC does not carry out its own scientific research, instead it informs the UN of existing relevant science. The following history of the UNFCCC’s formation explains how slow and ineffective the process has sadly been.
The first joint meeting of scientific bodies to assess CO2 in the atmosphere was held in 1980, between the United Nations Environment Programme (UNEP), International Council for Science (ICSU) and the World Meteorological Organisation (WMO).
At a 1985 meeting of the WMO, it was established that assessments be periodically undertaken of the state of scientific understanding of greenhouse gases and implications, and that a global convention to limit greenhouse gases be considered.
In 1988, the 43rd meeting of the UN General Assembly endorsed the formation of the Intergovernmental Panel on Climate Change (IPCC).
In mid-1992, 12 years after the first joint scientific meeting about CO2, the UN adopted for signature the Framework Convention on Climate Change. This was open for signature for two years before it “came into force” in mid-1994.8
Under this convention, the first annual meeting by signatory governments, named Conference Of Parties (COP), was held in 1995, in Berlin. Twenty one COPs were held before an agreement was finally reached to limit warming at COP21 in Paris.
During a summit in Paris in December 2015, organized under the United Nations Framework Convention on Climate Change (UNFCCC), 195 countries adopted the Paris Agreement which includes a long-term temperature goal:
“Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change;” (Article 2.1.a).
WMO, 2018, Understanding the IPCC Special Report on 1.5°C.9
“In order to achieve the long-term temperature goal set out in Article 2, Parties aim to reach global peaking of greenhouse gas emissions as soon as possible, recognizing that peaking will take longer for developing country Parties, and to undertake rapid reductions thereafter in accordance with best available science, so as to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century, on the basis of equity, and in the context of sustainable development and efforts to eradicate poverty.” (Article 4.1).
WMO, 2018, Understanding the IPCC Special Report on 1.5°C.9
It took until COP19 (nineteen annual meetings) just for an agreement to be reached to ‘work towards peaking emissions’,10 with an agreement to limit emissions ‘as soon as possible’ declared two further years later at COP21.1
In 2020, 5 years since the Paris Agreement, 26 years since the UNFCCC came into force, 32 years since the formation of the IPCC, and 40 years since the first joint scientific meeting about atmospheric CO2, annual CO2 emissions from fossil fuels and industry have soared. These emissions have increased 90% since 1980, when the first joint scientific meeting about CO2 was held, and 57% since COP1 in 1995.1112 To make matters worse: (i) limiting warming to 1.5℃ (the goal of the Paris Agreement) is not safe because when earth was last warmed 1.5℃, seas were 6 to 9m (20 to 30ft) higher; (ii) the scale of emission reductions prescribed are beyond any historic precedent;13 (iii) prescribed emission reductions depend on concurrent massive CO2 removal; 14 (iv) the annual increase of CO2 emissions is near record rate;15 and (v) 1.5℃ is imminent.16
CO2 emissions from fossil fuel combustion and cement: (i) in 1980 = 19.4GtCO2; (ii) in 1995 = 23.39GtCO2; and (iii) in 2019 = 36.8GtCO2. 2019 with respect to 1980 = 36.8/19.4 = +90%, and 2019 with respect to 1995 = 36.8/23.39 = +57%(↩)
Humanity’s fossil fuel CO2 emissions by country in 2018 are shown in chart 1.
But chart 22 shows China and India have contributed a much smaller share of total CO2 emitted since preindustrial times.
Furthermore, chart 3(a) shows that China’s per capita carbon emissions in 2016 were near global mean (or “average”), and India’s less. Chart 3(b) displays cumulative carbon emissions per capita from 1751 to 2018. This the the total quantity of carbon emissions emitted by each country since preindustrial times divided by the population of each country in 2018. China’s contribution is less than global mean and India’s contribution is tiny.
Those countries most to blame for climate change, and therefore should be leading wth radical mitigation, are those that have the highest cumulative-per-capita emissions: the U.S., U.K., Germany, Canada, Russia, Australia and Japan. Instead, these countries have been laggards as shown in Chart 4. (Although the UK’s emissions have declined, in 2017 the amount of CO2 emitted per unit of energy consumed has declined only to world average. The UK’s CO2 emissions were disproportionate due to a carbon-intensive energy system and industry)3
The most immediate priority of all nations is to make our climate safe and only science can prescribe the necessary changes. Arbitrary actions, that may be well intentioned, will be inadequate because there is no time remaining for half-measures.5
Arbitrary actions include carbon-offset schemes that may instead worsen matters because:
some are marketing lies, unable to withstand scrutiny;7
if credible, such carbon sinks should be implemented as rapidly as possible to help mitigate existing climate impacts, not instead used to clear the conscience of those indulging in carbon-intensive activities;
economies cannot be completely decarbonised, so countries will need to increase their natural carbon sinks to compensate, leaving no surplus to be used for offsetting;
1.5˚C emission-pathways depend on massive and currently unfeasible CO2 removal. The IPCC state ‘CDR deployed at scale is unproven, and reliance on such technology is a major risk in the ability to limit warming to 1.5°C’,8 In light of this, carbon sinks should be made available for CDR instead of offsets;
natural carbon sinks are subjected to disturbances that may permanently compromise their ability to sink carbon, or convert them to a carbon source (e.g. severe and or very frequent forest fire); and
carbon payback times for forests may be very long, making the intended carbon offset useless for limiting warming. Estimates vary from less than 20 years to centuries.9
Two prominent endeavours have pursued the stabilisation of greenhouse gases to limit warming: (i) 1.5˚C pathways by the IPCC and UNFCCC; and (ii) ‘350 ppm’, the work of Dr James Hansen and colleagues. These are explained in the following posts, and the most important finding of both is that decarbonisation alone will now be inadequate, and ‘negative emission technologies’ (NETs), otherwise known as ‘carbon dioxide removal’ (CDR) methods, are required. These negative emissions are a burden imposed on young people.10
p. 96, IPCC Special Report on 1.5°C, J. Rogelj, D. Shindell, K. Jiang, S. Fifita, P. Forster, V. Ginzburg, C. Handa, H. Kheshgi, S. Kobayashi, E. Kriegler, L. Mundaca, R. Séférian, M. V. Vilariño, 2018, Mitigation pathways compatible with 1.5°C in the context of sustainable development. In: Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [V. Masson-Delmotte, P. Zhai, H. O. Pörtner, D. Roberts, J. Skea, P. R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J. B. R. Matthews, Y. Chen, X. Zhou, M. I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, T. Waterfield (eds.)]. In Press. https://www.ipcc.ch/site/assets/uploads/sites/2/2018/11/SR15_Chapter2_Low_Res.pdf(↩)
Seasons vary year to year, being either cold, hot or mild examples. In order to measure trends of seasonal change, a histogram can be drawn showing the difference between the mean (or ‘average’) temperature of each month, and the long term mean for that month. These are known as temperature anomalies, and if over a sufficiently large area and long time, the results will be distributed in the shape of a bell, also known as a ‘normal distribution’.1
The bell curve will vary in width and height depending on the geographical area and time period being measured. The y-axis can be interpreted as “frequency of occurrence”, with the peak in the centre being the most frequently occurring value because it’s the mean.
Deviations from the mean in either direction, shown by the x-axis, represent cool or hot months for the season being plotted. To allow changes to be compared between time periods and or regions, the x-axis can be scaled as ‘number of standard deviations’ (i.e ‘Z-score’).2 The area under segments of the bell curve are shares of very cold to very hot months.
Shown below is the change of summer and winter monthly mean temperature distributions over land in the northern hemisphere, relative to 1951-80, with the latest displayed being 2005-2015. The period 1951-1980 is an often used reference period.
… the period 1951–80 is defined as a baseline for changes in heat extremes. This baseline has the advantage of having been a period of relatively stable global temperature, prior to rapid global warming, and of providing sufficient observational measurements such that the climatology is well defined.
World Bank. 2013. Turn down the heat : climate extremes, regional impacts, and the case for resilience.3
Since 1951-80, the share of northern hemisphere summer months categorised as ‘cold’ has decreased from 33.5% to just 5.8%, and the share of ‘very hot’ months has increased from 0.1% to 14.5%. The share of hot months has doubled.
The shifts of monthly mean temperature distributions over each hemisphere and various regions are shown below.
Note that over the African rainforest region and south east Asia, almost half of the months of each year between 2005-2015 were so hot, that they never occurred during 1951-1980. The same applies to summer in the Mediterranean and the Middle East.
Over the Australian mainland and Tasmania, between 1951-80 and 2010-2019, in all seasons, the share of cold months has decreased by about two thirds and the share of hot months has increased from about 14% to 40%. The share of very hot months has increased from a negligible amount to 4% in summer and autumn, 2% in winter and 6% in spring.
The shifts of monthly mean temperature distributions shown on this page are the consequence of 1.0˚C global mean surface air temperature as of 2015, and 1.1˚C in 2019, with respect to 1880-1910.10 The current policy of governments worldwide will result in 3.3˚C+ 11 and much larger shifts of temperature distributions.
Anthropogenic greenhouse gas emissions are a rapid planetary geoengineering experiment, without any plan, and without any known analogue.12
Biodiversity is affected by many agents including overharvesting, introduction of exotic species, land use changes, nitrogen fertilization, and direct effects of increased atmospheric CO2 on plant ecophysiology. However, an overriding role of climate change is exposed by diverse effects of rapid warming on animals, plants, and insects in the past three decades.
A sudden widespread decline of frogs, with extinction of entire mountain-restricted species attributed to global warming, provided a dramatic awakening. There are multiple causes of the detailed processes involved in global amphibian declines and extinctions, but global warming is a key contributor and portends a planetary-scale mass extinction in the making unless action is taken to stabilize climate while also fighting biodiversity’s other threats.
Mountain-restricted and polar-restricted species are particularly vulnerable. As isotherms move up the mountainside and poleward, so does the climate zone in which a given species can survive. If global warming continues unabated, many of these species will be effectively pushed off the planet. There are already reductions in the population and health of Arctic species in the southern parts of the Arctic, Antarctic species in the northern parts of the Antarctic, and alpine species worldwide.
A critical factor for survival of some Arctic species is retention of all-year sea ice. Continued growth of fossil fuel emissions will cause loss of all Arctic summer sea ice within several decades.
IPCC reviewed studies relevant to estimating eventual extinctions. They estimate that if global warming exceeds 1.6℃ above preindustrial, 9–31 percent of species will be committed to extinction. With global warming of 2.9℃, an estimated 21–52 percent of species will be committed to extinction.
Hansen et al., 2013, Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature.1
Seventeen years ago, in the mountains of Costa Rica, the Monteverde harlequin frog (Atelopus sp.) vanished along with the golden toad (Bufo periglenes). An estimated 67% of the 110 or so species of Atelopus, which are endemic to the American tropics, have met the same fate, and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) is implicated. Analysing the timing of losses in relation to changes in sea surface and air temperatures, we conclude with ‘very high confidence’ (> 99%, following the Intergovernmental Panel on Climate Change, IPCC) that large-scale warming is a key factor in the disappearances. We propose that temperatures at many highland localities are shifting towards the growth optimum of Batrachochytrium, thus encouraging outbreaks. With climate change promoting infectious disease and eroding biodiversity, the urgency of reducing greenhouse-gas concentrations is now undeniable.
Pounds et al., 2006, Widespread amphibian extinctions from epidemic disease driven by global warming.2
Despite increase of vegetation available for grazing, herd populations of caribou and wild reindeer across the Arctic tundra have declined by nearly 50% over the last two decades.
Among the most clear and profound influences of climate change on the world’s oceans are its impacts on habitat-forming species such as corals, sea grass, mangroves, salt marsh grasses, and oysters. Collectively, these organisms form the habitat for thousands of other species. Although some resident species may not have absolute requirements for these habitats, many do, and they disappear if the habitat is removed. For example, mass coral bleaching and mortality, the result of increasing temperatures, is already reducing the richness and density of coral reef fishes and other organisms.
Hoegh-Guldberg et al., 2010, The impact of climate change on the world’s marine ecosystems.4
It was not until the global bleaching event of 1982–1983 that widespread bleaching and mortality were recognised as a major phenomenon that could impact coral reef status and health at regional and global scales.
Oppen et al., 2018, Coral bleaching: patterns, processes, causes and consequences.5
Coral reefs provide some of the most biologically rich, productive and economically valuable ecosystems on Earth. Over 25 per cent of all marine species live in coral reefs, and yet they cover less than 0.1 per cent of the ocean, about half the area of France.
Globally, around 850 million people live within 100km of a coral reef and directly benefit from the economic, social and cultural services it provides. Reefs support many economically important fish species, providing food for hundreds of millions of people. They also protect the coast from storms and erosion, and generate jobs and income from fishing, tourism and recreation.
The Great Barrier Reef – which, at 1,400 miles long, is the longest and largest coral reef in the world – was blanketed by dangerously hot water in the summer of 2016. This heat strangled and starved the corals, causing what has been called “an unprecedented bleaching event.”
The Atlantic, 2018, Since 2016, Half of All Coral in the Great Barrier Reef Has Died.7
“On average, across the Great Barrier Reef, one in three corals died in nine months,” said Terry Hughes, an author of the paper and the director of the ARC Center of Excellence for Coral Reef Studies, the Australian government’s federal research program devoted to corals.
About 50 percent of all the coral that perished in the 2016 bleaching event died in the autumn and winter, long after temperatures had returned to normal. Those corals never regained their algae after evicting them, and they slowly starved to death.
“But about half of the corals that died did so in March, at the peak of summer temperatures,” Hughes told me. “We were surprised that about half of that mortality occurred very quickly.”
In other words, some corals did not even survive long enough to starve. “They died instantly, of heat stress,” Hughes said. “They cooked.”
Yet it was not the end of troubles for the Great Barrier Reef. In the summer months of 2017, warm waters again struck the reef and triggered another bleaching event. This time, the heat hit the reef’s middle third. Hughes and his team have not published a peer-reviewed paper on that event, but he shared early survey results with me.
Combined, he said, the back-to-back bleaching events killed one in every two corals in the Great Barrier Reef. It is a fact almost beyond comprehension: In the summer of 2015, more than 2 billion corals lived in the Great Barrier Reef. Half of them are now dead.
The study fits into a streak of dreary findings for coral reefs. If the world were to warm by an average of 2 degrees Celsius, then ocean temperatures would consistently exceed their 2016 levels, even during non-El Niño years, a recent study in Nature Climate Change found.9 In another study, released in January, scientists surveyed observations of 100 coral reefs around the world going back 35 years. They found that mass bleaching events now strike five times more often than they did in the early 1980s.10
The Atlantic, 2018, Since 2016, Half of All Coral in the Great Barrier Reef Has Died.7
More than 70% of coral reefs around the world experienced the heat stress that can cause bleaching and/or mortality during the three-year long global event.
Multiple coral reef ecosystems around the world experienced severe bleaching in back–to–back years, including areas like Guam, where corals bleached every year from 2013 to 2017. As of the end of May 2017, the third global coral bleaching event most likely ended 12 but will remain the longest, most widespread, and possibly the most damaging coral bleaching event on record.13 It affected more reefs than any previous global bleaching event and was worse in some locales (e.g., Great Barrier Reef, Kiribati, Jarvis Island). Heat stress during this event also caused mass bleaching in several reefs that never bleached before (e.g., northernmost Great Barrier Reef).
Recurrent regional-scale (>1000 km) bleaching and mortality of corals is a modern phenomenon caused by anthropogenic global warming. Bleaching before the 1980s was recorded only at a local scale of a few tens of kilometers because of small-scale stressors such as freshwater inundation, sedimentation, or unusually cold or hot weather.
Our findings reveal that coral reefs have entered the distinctive human-dominated era characterized as the Anthropocene, in which the frequency and intensity of bleaching events is rapidly approaching unsustainable levels.
At the spatial scale we examined, the number of years between recurrent severe bleaching events has diminished fivefold in the past four decades, from once every 25 to 30 years in the early 1980s to once every 5.9 years in 2016.
The time between recurrent events is increasingly too short to allow a full recovery of mature coral assemblages, which generally takes from 10 to 15 years for the fastest growing species and far longer for the full complement of life histories and morphologies of older assemblages.
Hughes et al., 2018, Spatial and temporal patterns of mass bleaching of corals in the Anthropocene.15
The summer of 2016 remains one of the most severe coral bleaching and die-off events ever observed14—a level of devastation that scientists didn’t expect to see until the 2050s. A new study argues that it will not remain a rare event for long. Even in simulations of the most hopeful global-warming scenarios, modern climate models suggest that ocean temperatures around the Great Barrier Reef will regularly surpass the devastating warmth of 2016.
In a 1.5-degree world, there’s still about a two-thirds chance that any summer would bring 2016-level heat to the Great Barrier Reef. And even in the coolest, kindest of the scenarios—the “gentlest” version of a 1.5-degree world—the odds of 2016-level heat are just over 50 percent. The reef would bleach every other year.
The Atlantic, 2017, The Great Barrier Reef Is Probably Doomed No Matter What.9
Marine heatwaves have also devastated kelp forests. “Kelp is a type of seaweed (or marine algae) that describes 27 genera worldwide. Some kelps form dense patches on rocky reefs resembling a forest of trees underwater and are referred to as kelp forests.”16
The first global study of kelp forest change over 50 years concluded that kelp had declined in 38% of the 1,138 sites studied globally.17
A hundred kilometres of kelp forests off the western coast of Australia were wiped out by a marine heatwave between 2010 and 2013, a new study has revealed.18
About 90% of the forests that make up the north-western tip of the Great Southern Reef disappeared over the period, replaced by seaweed turfs, corals, and coral fish usually found in tropical and subtropical waters.
The Great Southern Reef is a system of rocky reefs covered by kelp forests that runs along the south coast of Australia, extending past Sydney on the east coast, down to Tasmania and, previously, back up to Kalbarri on the west coast.
It supports most of the nation’s fisheries, including the lucrative rock lobster and abalone fisheries, and is worth about $10bn to the Australian economy. It is also a global biodiversity hotspot, with up to 30% of species endemic.
The Guardian, 2016, Australia’s vast kelp forests devastated by marine heatwave, study reveals.19
Today, more than 95 percent of eastern Tasmania’s kelp forests — luxuriant marine environments that provide food and shelter for species at all levels of the food web — are gone. With the water still warming rapidly and the long-spine urchin spreading southward in the favorable conditions, researchers see little hope of saving the vanishing ecosystem.
“Our giant kelp forests are now a tiny fraction of their former glory,” says Craig Johnson, a researcher at the University of Tasmania’s Institute for Marine and Antarctic Studies.20 “This ecosystem used to be a major iconic feature of eastern Tasmania, and it no longer is.”
The Tasmanian saga is just one of many examples of how climate change and other environmental shifts are driving worldwide losses of giant kelp, a brown algae whose strands can grow to 100 feet. In western Australia, increases in ocean temperatures, accentuated by an extreme spike in 2011, have killed vast beds of an important native kelp.
In southern Norway, ocean temperatures have exceeded the threshold for sugar kelp which has died en masse since the late 1990s and largely been replaced by thick mats of turf algae, which stifles kelp recovery.
In western Europe, the warming Atlantic Ocean poses a serious threat to coastal beds of kelp, and researchers21 have predicted “extirpation of the species as early as the first half of the 21st century” in parts of France, Denmark, and southern England.
YaleEnvironment360, 2017, As Oceans Warm, the World’s Kelp Forests Begin to Disappear.22
Ecology and the Environment
The ecological impact of fossil fuel mining increases as the largest, easiest to access, resources are depleted. A constant fossil fuel production rate requires increasing energy input, but also use of more land, water, and diluents, with the production of more waste.
Coal mining has progressively changed from predominantly underground mining to surface mining, including mountaintop removal with valley fill, which is now widespread in the Appalachian ecoregion in the United States. Forest cover and topsoil are removed, explosives are used to break up rocks to access coal, and the excess rock is pushed into adjacent valleys, where it buries existing streams. Burial of headwater streams causes loss of ecosystems that are important for nutrient cycling and production of organic matter for downstream food webs. The surface alterations lead to greater storm runoff with likely impact on downstream flooding. Water emerging from valley fills contain toxic solutes that have been linked to declines in watershed biodiversity. Even with mine-site reclamation intended to restore pre-mined surface conditions, mine-derived chemical constituents are found in domestic well-water. Reclaimed areas have been found to produce little if any regrowth of woody vegetation even after 15 years, and, although this deficiency might be addressed via more effective reclamation methods, there remains a likely significant loss of carbon storage.
Oil mining has an increasing ecological footprint per unit delivered energy because of the decreasing size of new fields and their increased geographical dispersion; transit distances are greater and wells are deeper, thus requiring more energy input. Useful quantitative measures of the increasing ecological impacts are provided by the history of oil development in Alberta, Canada for production of both conventional oil and tar sands development. The area of land required per barrel of produced oil increased by a factor of 12 between 1955 and 2006 leading to ecosystem fragmentation by roads and pipelines needed to support the wells. Additional escalation of the mining impact occurs as conventional oil mining is supplanted by tar sands development, with mining and land disturbance from the latter producing land use-related greenhouse gas emissions as much as 23 times greater than conventional oil production per unit area, but with substantial variability and uncertainty. Much of the tar sands bitumen is extracted through surface mining that removes the ‘‘overburden’’ (i.e., boreal forest ecosystems) and tar sand from large areas to a depth up to 100 m, with ecological impacts downstream and in the mined area. Although mined areas are supposed to be reclaimed, as in the case of mountaintop removal, there is no expectation that the ecological value of reclaimed areas will be equivalent to predevelopment condition. Landscape changes due to tar sands mining and reclamation cause a large loss of peatland and stored carbon, while also significantly reducing carbon sequestration potential. Lake sediment cores document increased chemical pollution of ecosystems during the past several decades traceable to tar sands development and snow and water samples indicate that recent levels of numerous pollutants exceeded local and national criteria for protection of aquatic organisms.
Gas mining by unconventional means has rapidly expanded in recent years, without commensurate understanding of the ecological, environmental and human health consequences. The predominant approach is hydraulic fracturing (‘‘fracking’’) of deep shale formations via injection of millions of gallons of water, sand and toxic chemicals under pressure, thus liberating methane. A large fraction of the injected water returns to the surface as wastewater containing high concentrations of heavy metals, oils, greases and soluble organic compounds. Management of this wastewater is a major technical challenge, especially because the polluted waters can continue to backflow from the wells for many years. Numerous instances of groundwater and river contamination have been cited. High levels of methane leakage from fracking have been found, as well as nitrogen oxides and volatile organic compounds. Methane leaks increase the climate impact of shale gas, but whether the leaks are sufficient to significantly alter the climate forcing by total natural gas development is uncertain. Overall, environmental and ecologic threats posed by unconventional gas extraction are uncertain because of limited research, however evidence for groundwater pollution on both local and river basin scales is a major concern.
Hansen et al., 2013, Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature.23
Impacts of climate change cause widespread harm to human health, with children often suffering the most. Food shortages, polluted air, contaminated or scarce supplies of water, an expanding area of vectors causing infectious diseases, and more intensely allergenic plants are among the harmful impacts. More extreme weather events cause physical and psychological harm. World health experts have concluded with ‘‘very high confidence’’ that climate change already contributes to the global burden of disease and premature death.
IPCC projects the following trends, if global warming continues to increase, where only trends assigned very high confidence or high confidence are included: (i) increased malnutrition and consequent disorders, including those related to child growth and development, (ii) increased death, disease and injuries from heat waves, floods, storms, fires and droughts, (iii) increased cardio-respiratory morbidity and mortality associated with ground-level ozone. While IPCC also projects fewer deaths from cold, this positive effect is far outweighed by the negative ones.
Growing awareness of the consequences of human-caused climate change triggers anxiety and feelings of helplessness. Children, already susceptible to age-related insecurities, face additional destabilizing insecurities from questions about how they will cope with future climate change. Exposure to media ensures that children cannot escape hearing that their future and that of other species is at stake, and that the window of opportunity to avoid dramatic climate impacts is closing. The psychological health of our children is a priority, but denial of the truth exposes our children to even greater risk.
Hansen et al., 2013, Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature, p. 6.1
In 2013 and 2014, the World Bank Group published a series of reports detailing how climate change impacts will be felt disproportionately in developing countries around the equatorial regions.2
2013 report –
With a focus on Sub-Saharan Africa, South East Asia and South Asia, the report examines in greater detail the likely impacts for affected populations of present day, 2°C and 4°C warming on critical areas like agricultural production, water resources, coastal ecosystems and cities.
The result is a dramatic picture of a world of climate and weather extremes causing devastation and human suffering. In many cases, multiple threats of increasing extreme heat waves, sea-level rise, more severe storms, droughts and floods will have severe negative implications for the poorest and most vulnerable.
In Sub-Saharan Africa, significant crop yield reductions with 2°C warming are expected to have strong repercussions on food security, while rising temperatures could cause major loss of savanna grasslands threatening pastoral livelihoods. In South Asia, projected changes to the monsoon system and rising peak temperatures put water and food resources at severe risk. Energy security is threatened, too. While, across South East Asia, rural livelihoods are faced with mounting pressures as sea-level rises, tropical cyclones increase in intensity and important marine ecosystem services are lost as warming approaches 4°C.
Across all regions, the likely movement of impacted communities into urban areas could lead to ever higher numbers of people in informal settlements being exposed to heat waves, flooding, and diseases.
World Bank. 2013. Turn Down the Heat: Climate Extremes, Regional Impacts, and the Case for Resilience.3
2014 report –
For this report, the third in the Turn Down the Heat series, we turned again to the scientists at the Potsdam Institute for Climate Impact Research and Climate Analytics. We asked them to look at the likely impacts of present day (0.8°C), 2°C and 4°C warming on agricultural production, water resources, cities and ecosystems across Latin America and the Caribbean, Middle East and North Africa, and parts of Europe and Central Asia.
Their findings are alarming.
In Latin America and the Caribbean, heat extremes and changing precipitation patterns will have adverse effects on agricultural productivity, hydrological regimes and biodiversity. In Brazil, at 2°C warming, crop yields could decrease by up to 70 percent for soybean and up to 50 percent for wheat. Ocean acidification, sea level rise, tropical cyclones and temperature changes will negatively impact coastal livelihoods, tourism, health and food and water security, particularly in the Caribbean. Melting glaciers would be a hazard for Andean cities.
In the Middle East and North Africa, a large increase in heat-waves combined with warmer average temperatures will put intense pressure on already scarce water resources with major consequences for regional food security. Crop yields could decrease by up to 30 percent at 1.5–2°C and by almost 60 percent at 3–4°C. At the same time, migration and climate-related pressure on resources might increase the risk of conflict.
In the Western Balkans and Central Asia, reduced water availability in some places becomes a threat as temperatures rise toward 4°C. Melting glaciers in Central Asia and shifts in the timing of water flows will lead to less water resources in summer months and high risks of torrential floods. In the Balkans, a higher risk of drought results in potential declines for crop yields, urban health, and energy generation. In Macedonia, yield losses are projected of up to 50 percent for maize, wheat, vegetables and grapes at 2°C warming. In northern Russia, forest dieback and thawing of permafrost threaten to amplify global warming as stored carbon and methane are released into the atmosphere, giving rise to a self-amplifying feedback loop.
World Bank. 2014. Turn Down the Heat: Confronting the New Climate Normal.4
Under all three scenarios in this report, there is an upward trend of internal climate migration in Sub-Saharan Africa, South Asia, and Latin America by 2050. In the worst-case or “pessimistic” scenario, the number of internal climate migrants could reach more than 143 million (around 86 million in Sub-Saharan Africa, 40 million in South Asia, and 17 million in Latin America) by 2050. The poorest people and the poorest countries are the hardest hit.
Across all scenarios, climate change is a growing driver of internal migration. Climate change impacts (crop failure, water stress, sea level rise) increase the probability of migration under distress, creating growing challenges for human development and planning. Vulnerable people have the fewest opportunities to adapt locally or to move away from risk and, when moving, often do so as a last resort. Others, even more vulnerable, will be unable to move, trapped in increasingly unviable areas.
Internal climate migration will intensify over the next several decades and could accelerate after 2050 under the pessimistic scenario due to stronger climate impacts combined with steep population growth in many regions.
World Bank Group, 2018, Groundswell – Preparing for internal climate migration.5
World Bank. 2013. Turn Down the Heat: Climate Extremes, Regional Impacts, and the Case for Resilience. A report for the World Bank by the Potsdam Institute for Climate Impact Research and Climate Analytics. Washington, DC:World Bank. License: Creative Commons Attribution—NonCommercial–NoDerivatives3.0 Unported license (CC BY-NC-ND 3.0), http://www.worldbank.org/en/topic/climatechange/publication/turn-down-the-heat(↩)
Organisation of this and the following two posts is adapted from the paper ‘Assessing ‘‘Dangerous Climate Change’’: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature’.1
Global warming is rapidly melting Arctic sea ice, thereby triggering a fast amplifying feedback that drives further warming. This is known as polar amplification or the sea ice/ocean surface albedo feedback: “With retreating sea ice, surface albedo decreases, air temperatures increase and the ocean can absorb more heat. The resulting ocean warming contributes to further sea ice melting.”2
Sea ice helps to keep the Arctic atmosphere cold. Its whiteness reflects much of the Sun’s energy back to space, and it physically insulates the Arctic atmosphere from the underlying Arctic Ocean. With less sea ice, more dark open water is exposed, which readily absorbs the Sun’s energy in summer, heating the ocean and leading to even more melt. With less sea ice there is also less insulation, so that heat from the ocean escapes to warm the atmosphere in the autumn and winter.
Surface air temperatures in the Arctic continued to warm at twice the rate relative to the rest of the globe. Arctic air temperatures for the past five years (2014-18) have exceeded all previous records since 1900.
In 2018 Arctic sea ice remained younger, thinner, and covered less area than in the past. The 12 lowest extents in the satellite record have occurred in the last 12 years.
Dr. Osborne, the lead editor of the report and manager of NOAA’s Arctic Research Program, said the Arctic was undergoing its “most unprecedented transition in human history.”
In 2018, “warming air and ocean temperatures continued to drive broad long-term change across the polar region, pushing the Arctic into uncharted territory,” she said at a meeting of the American Geophysical Union in Washington.
NYT, 2018, Warming in Arctic Raises Fears of a ‘Rapid Unraveling’ of the Region.6
Arctic sea ice extent7 increases during the colder months, reaching a maximum in March, and decreases in the warmer months, reaching a minimum in September. This cycle is shown below.
Arctic sea ice extent during warm months has declined to 60% of the 1979-90 mean (i.e. average) for each month.
The following video explains the decline of the annual creation and extent of Arctic sea ice.
Older, and therefore thicker Arctic sea ice has almost completely disappeared:
Over the past three decades of global warming, the oldest and thickest ice in the Arctic has declined by a stunning 95 percent, according the National Oceanic and Atmospheric Administration’s annual Arctic Report Card.11
The finding suggests that the sea at the top of the world has already morphed into a new and very different state, with major implications not only for creatures such as walruses and polar bears but, in the long term, perhaps for the pace of global warming itself.
Increasingly, what remains is ice that only forms after the peak warmth of the summer, usually in September, and which may not survive the following summer. This “first year ice” is more brittle, more easily tossed around by winds and waves, rendering the Arctic ice pack more mobile and prone to breaking apart.
In 1985, the new NOAA report found, 16 percent of the Arctic was covered by the very oldest ice, more than four years old, at the height of winter. But by March, that number had dropped to under 1 percent. That’s a 95 percent decline.
At the same time, the youngest, first-year ice has gone from 55 percent of the pack in the 1980s to 77 percent, the report finds. (The remainder is ice that is two to three years old.)
The Washington Post, 2018, The Arctic Ocean has lost 95 percent of its oldest ice — a startling sign of what’s to come.12
This process of reverse-aging, scientists say, is all headed to a crucial moment — when all of the ice in the Arctic will be thin and a year old or less. When that happens — the day of maximum youth — we will be on the verge of a much feared milestone: an entirely ice-free Arctic Ocean in summer. “Looking down from the North Pole from above, for all intents and purposes, you’re going to see a blue Arctic Ocean” Meier said.14
Ramanathan15 fears that entirely ice-free summers, if they began to occur regularly, could add another half-degree Celsius (0.9 degrees Fahrenheit) of warming on top of whatever else the planet has experienced by that time. “If that were to happen, I would think of it as an unmitigated disaster,” said Ramanathan of consistently ice-free Arctic summers. “It will quickly pump in this half a degree warming.”
The Washington Post, 2018, The Arctic Ocean has lost 95 percent of its oldest ice — a startling sign of what’s to come.12
A striking consequence of global warming16 is rapid retreat of glaciers, such as the Upsala glacier in the Southern Andes:
The charts below show the obvious global trend of glacier retreat:
Glaciers in Alaska have dramatically retreated:
Water from glacial runoff is an important supply for some cities and rural communities, for agricultural production and for hydroelectric power generation. Glaciers help to regulate streamflow in regions where water is stored during colder periods of the year, and later released as melt water runoff during warm dry conditions.22 An example of this is the Chacaltaya glacier, that was a supply of water for drinking and hydroelectric power in Bolivia’s main cities, La Paz and El Alto.23 The three main dams that supply these cities are no longer fed by runoff from glaciers and have almost run dry. Water rationing was introduced and the armed forces were brought in to distribute water while emergency wells were drilled.24
p.6, Hansen J, Kharecha P, Sato M, Masson-Delmotte V, Ackerman F, Beerling DJ, et al. (2013) Assessing “Dangerous Climate Change”: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature. PLoS ONE 8(12): e81648. https://doi.org/10.1371/journal.pone.0081648(↩)
Box 5.1, page 396, Masson-Delmotte, V., M. Schulz, A. Abe-Ouchi, J. Beer, A. Ganopolski, J.F. González Rouco, E. Jansen, K. Lambeck, J. Luterbacher, T. Naish, T. Osborn, B. Otto-Bliesner, T. Quinn, R. Ramesh, M. Rojas, X. Shao and A. Timmermann, 2013: Information from Paleoclimate Archives. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. https://www.ipcc.ch/report/ar5/wg1/(↩)
The difference between extent and area is explained at https://nsidc.org/arcticseaicenews/faq/#area_extent This states “A simplified way to think of extent versus area is to imagine a slice of Swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. That is why if you compare extent and area in the same time period, extent is always bigger. Scientists at NSIDC report extent because they are cautious about summertime values of ice concentration and area taken from satellite sensors. To the sensor, surface melt appears to be open water rather than water on top of sea ice.”(↩)
Walt Meier, a sea ice expert at the National Snow and Ice Data Center(↩)
Veerabhadran Ramanathan is a climate expert at the Scripps Institution of Oceanography who was the discoverer of the role of chlorofluorocarbons (or CFCs) in not only destroying the ozone layer but also amplifying global warming. Refer to https://scripps.ucsd.edu/labs/ramanathan/(↩)
See FAQ 10.1 on page 894 of Bindoff, N.L., P.A. Stott, K.M. AchutaRao, M.R. Allen, N. Gillett, D. Gutzler, K. Hansingo, G. Hegerl, Y. Hu, S. Jain, I.I. Mokhov, J. Overland, J. Perlwitz, R. Sebbari and X. Zhang, 2013: Detection and Attribution of Climate Change: from Global to Regional. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter10_FINAL.pdf(↩)
Vaughan, D.G., J.C. Comiso, I. Allison, J. Carrasco, G. Kaser, R. Kwok, P. Mote, T. Murray, F. Paul, J. Ren, E. Rignot, O. Solomina, K. Steffen and T. Zhang, 2013: Observations: Cryosphere. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter04_FINAL.pdf(↩)
Tielidze, L. G.: Glacier change over the last century, Caucasus Mountains, Georgia, observed from old topographical maps, Landsat and ASTER satellite imagery, The Cryosphere, 10, 713-725, https://doi.org/10.5194/tc-10-713-2016, 2016.(↩)
We face a direct existential threat… Extreme heatwaves, wildfires, storms and floods are leaving a trail of death and devastation… We are careering towards the edge of the abyss.
UN, 2018, UN Secretary-General’s press encounter on climate change.1
Despite repeated warnings about climate change, civilisation has chosen not to be precautionary. Instead it chooses to be reckless and hold climate science in contempt by endorsing politicians who fail to act, and to indulge in oil, coal and gas. And so our climate radically changes along with Earth’s land and ocean, on vast scales at extreme rates. Civilisation chooses indifference, leaving a nightmarish burden for young people.
Climate change is now an existential threat to civilisation, not only because of changes due to the warming from our GHG emissions, but because of feedbacks. Feedbacks act on different timescales, so some are fast and others are slow, and they are either negative feedbacks that reduce an impact, or positive feedbacks that amplify. Our emissions have already set in play fast amplifying feedbacks in Earth’s climate system, and are now triggering additional further amplifying feedbacks associated with Earth’s ice-sheets that may take the climate system past tipping points. These are points of no return, with consequences beyond our control.
The current rate of global warming could raise sea levels by “several meters” over the coming century, rendering most of the world’s coastal cities uninhabitable and helping unleash devastating storms, according to a paper published by James Hansen, the former Nasa scientist who is considered the father of modern climate change awareness.
The Guardian, 2016, Climate guru James Hansen warns of much worse than expected sea level rise.2
The abundant empirical evidence of the unprecedented rate and global scale of impact of human influence on the Earth System has led many scientists to call for an acknowledgement that the Earth has entered a new geological epoch: the Anthropocene. The rise in global CO2 concentration since 2000 is about 20 ppm per decade, which is up to 10 times faster than any sustained rise in CO2 during the past 800,000 years. AR5 (the IPCC fifth assessment report)3 found that the last geological epoch with similar atmospheric CO2 concentration was the Pliocene, 3.3 to 3.0 Ma (million years ago). Since 1970 the global average temperature has been rising at a rate of 1.7°C per century, compared to a long-term decline over the past 7,000 years at a baseline rate of 0.01°C per century. These global-level rates of human-driven change far exceed the rates of change driven by geophysical or biosphere forces that have altered the Earth System trajectory in the past; even abrupt geophysical events do not approach current rates of human-driven change.
IPCC (2018), Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways.4
Humanity’s CO2 emissions: (i) are currently trapping two thirds of the energy causing global warming, (ii) are the only rapidly increasing contributor, (iii) almost solely determine our long term warming commitment, and (iv) continue to grow with no peak in sight. Half of all CO2 ever emitted has been emitted recently and almost all by the world’s energy system.5
The World Meteorological Organisation (WMO) points out that CO2 annual rates of change since preindustrial times have been, and still are, about 10 times faster than the fastest natural change, and that levels of atmospheric CO2 concentration are now similar to climates million of years in the past when seas were much higher.6
The increase in CO2 from 2015 to 2016 was larger than the increase observed from 2014 to 2015 and the average over the last decade. Direct measurements of atmospheric CO2 over the past 800,000 years provide proof that over the past eight swings between ice ages (glacials) and warm periods similar to today (interglacials) atmospheric CO2 varied between 180 and 280 parts per million (ppm), demonstrating that today’s CO2 concentration of 400ppm exceeds the natural variability seen over hundreds of thousands of years. Over the past decade, new high-resolution ice core records have been used to investigate how fast atmospheric CO2 changed in the past. After the last ice age, some 23,000 years ago, CO2 concentrations and temperature began to rise. During the period recorded in the West Antarctica ice core, fastest CO2 increases (16,000, 15,000 and 12,000 years ago) ranged between 10 and 15ppm over 100–200 years. In comparison, CO2 has increased by 120ppm in the last 150 years due to combustion of fossil fuel. Periods of the past with a CO2 concentration similar to the current one can provide estimates for the associated “equilibrium” climate. In the mid-Pliocene, 3–5 million years ago, the last time that the Earth’s atmosphere contained 400ppm of CO2, global mean surface temperature was 2–3℃ warmer than today, the Greenland and West Antarctic ice sheets melted and even some of the East Antarctic ice was lost, leading to sea levels that were 10–20m higher than they are today. During the mid-Miocene (15–17 million years ago), atmospheric CO2 reached 400–650ppm and global mean surface temperature was 3–4℃ warmer than today.
Plausibly the most severe climate change impact would be rapid and large sea level rise from the collapse of Earth’s ice sheets – the Greenland ice sheet, the West Antarctic ice sheet (WAIS) and the East Antarctic ice sheet (EAIS). This impact alone is a threat to the existence of global civilisation not only because of greater coastal flooding and storm surges, but also the financial and economic ramifications from the flooding of wealthy cities and ports, and the interruptions to international trade.
Shown below is land area in 2050 projected to be below annual flood level, due to 26cm sea level rise relative to year 2000.
Ice sheets, as opposed to ice shelfs, sit on bedrock that may be above or below sea level, and are dynamic – continuously gaining and losing mass. They gain mass from snow and rain that falls on them, which accumulates and compacts to form ice. This ice gradually drains to the ocean via rivers of ice known as glaciers which may terminate at the ocean, making them marine terminated glaciers. The point where an ice-sheet leaves the bedrock it rests upon, and becomes afloat is known as the grounding line. Here, the flow of ice leaves land and floats on the ocean surface, forming a tongue of ice known as an ice shelf.
Global warming has caused the flow rate of the glaciers that drain Greenland and WAIS to increase, putting the ice sheets out of mass balance (more ice going out, than forming from falling snow and rain), and their grounding lines have rapidly retreated.13
There are characteristics unique to the Antarctic ice sheet (AIS) that may cause rapid and large loss of ice, due to the amplifying feedback processes known as Marine Ice-Sheet Instability (MISI) and Marine Ice-Cliff Instability (MICI).
In contrast to the land-based East Antarctic ice sheet, the marine ice sheet in West Antarctica can exist only so long as its grounded position is buttressed by fringing ice shelves; in particular by the Ross and Filchner-Ronne ice shelves. Thus any environmental change that diminished or destroyed these ice shelves would also diminish or destroy the ice grounded below sea level; as the ice shelf fronts receded southward, their grounding lines would also recede and the grounded ice sheet would shrink and thin. Eventually after all the ice shelves had disappeared, ice cover would be confined to areas above sea level, and glaciers would terminate in ice cliffs between high and low water levels.
Mercer, J. (1978), West Antarctic ice sheet and CO2 greenhouse effect: a threat of disaster.16
Marine ice sheet and ice cliff instabilities
As far as anyone knows, no human had ever set foot on the West Antarctica glaciers until the International Geophysical Year, in 1957, a Cold War collaboration of the U.S. and the Soviet Union and other nations to expand the boundaries of scientific exploration. A team of scientists had trekked across the glaciers of West Antarctica, including Thwaites; by drilling ice cores and taking other measurements, they discovered that the ground beneath the ice was on a reverse slope and had been depressed further by the weight of the glaciers over millions of years. “Think of it as a giant soup bowl filled with ice,” says Sridhar Anandakrishnan, an expert in polar glaciology at Penn State University.
Marine ice sheets rest on bedrock that is submerged below sea level (often by 2 to 3 km). The most well-researched marine ice sheet is the West Antarctic ice sheet (WAIS) where approximately 75% of the ice sheet’s area currently rests on bedrock below sea level. The East Antarctic ice sheet (EAIS), however, also has appreciable areas grounded below sea level (~35%), in particular around the Totten and Cook Glaciers.
Information on the ice and bed topography of WAIS suggests that it has about 3.3 m of equivalent global sea level grounded on areas with downward sloping bedrock.
These ice sheets are fringed by floating ice shelves, which are fed by flow from grounded ice across a grounding line (GL). The GL is free to migrate both seawards and landwards as a consequence of the local balance between the weight of ice and displaced ocean water. Depending on a number of factors, which include ice-shelf extent and geometry, ice outflow to the ocean generally (but not always) increases with ice thickness at the GL. Accordingly, when the ice sheet rests on a bed that deepens towards the ice-sheet interior, the ice outflow to the ocean will generally increase as the GL retreats. It is this feature that gives rise to the Marine Ice-Sheet Instability (MISI), which states that a GL cannot remain stable on a landward-deepening slope.
IPCC (2013), Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.18
Much of the WAIS sits on bedrock hundreds to thousands of metres below sea level. Today, extensive floating ice shelves in the Ross and Weddell Seas, and smaller ice shelves and ice tongues in the Amundsen and Bellingshausen seas provide buttressing that impedes the seaward flow of ice and stabilizes marine grounding zones. Despite their thickness (typically about 1 km near the grounding line to a few hundred metres at the calving front), a warming ocean has the potential to quickly erode ice shelves from below, at rates exceeding 10 m/yr/°C. Ice-shelf thinning and reduced backstress enhance seaward ice flow, grounding-zone thinning, and retreat. Because the flux of ice across the grounding line increases strongly as a function of its thickness, initial retreat onto a reverse-sloping bed (where the bed deepens and the ice thickens upstream) can trigger a runaway Marine Ice Sheet Instability (MISI).
DeConto, R., Pollard, D. (2016), Contribution of Antarctica to past and future sea-level rise.19
The following quote refers to the image above.
Another physical mechanism previously under appreciated at the ice-sheet scale involves the mechanical collapse of ice cliffs in places where marine-terminating ice margins approach 1 km in thickness, with >90 m of vertical exposure above sea level. Today, most Antarctic outlet glaciers with deep beds approaching a water depth of 1 km are protected by buttressing ice shelves, with gently sloping surfaces at the grounding line (Fig. 2d). However, given enough atmospheric warming above or ocean warming below (Fig. 2e), ice-shelf retreat can outpace its dynamically accelerated seaward flow as buttressing is lost and retreating grounding lines thicken. In places where marine-terminating grounding lines are thicker than 800 m or so, this would produce >90 m subaerial cliff faces that would collapse (Fig. 2f ) simply because longitudinal stresses at the cliff face would exceed the yield strength (about 1 MPa) of the ice. More heavily crevassed and damaged ice would reduce the maximum supported cliff heights. If a thick, marine-terminating grounding line began to undergo such mechanical failure, its retreat would continue unabated until temperatures cooled enough to reform a buttressing ice shelf, or the ice margin retreated onto bed elevations too shallow to support the tall, unstable cliffs. If protective ice shelves were suddenly lost in the vast areas around the Antarctic margin where reverse-sloping bedrock is more than 1,000 m deep, exposed grounding-line ice cliffs would quickly succumb to structural failure, as is happening in the few places where such conditions exist today (the Helheim and Jakobsavn glaciers on Greenland and the Crane Glacier on the Antarctic Peninsula), hinting that a Marine Ice Cliff Instability (MICI) in addition to MISI could be an important contributor to past and future ice-sheet retreat.
DeConto, R., Pollard, D. (2016), Contribution of Antarctica to past and future sea-level rise.19
Major ice loss from the AIS stems from an increased discharge of grounded ice into the ocean, with ice shelves (the floating extensions of the grounded ice sheet) playing a crucial role. The buttressing provided by ice shelves can affect inland ice hundreds of kilometres away, and hence controls grounding-line retreat and associated ice flow acceleration. Ice shelves are directly affected by oceanic and atmospheric conditions, and any change in these conditions may alter their buttressing effect and impact the glaciers feeding them. For instance, increased sub-shelf melting causes ice shelves to thin, increasing their sensitivity to mechanical weakening and fracturing. This causes changes in ice shelf rheology and reduces buttressing of the inland ice, leading to increased ice discharge. Warming of the atmosphere promotes rainfall and surface melt on the ice shelves and causes hydrofracturing as water present at the ice-sheet surface propagates into crevasses or by tensile stresses induced by lake drainage.
Reduction of buttressing of ice shelves via the processes described above may eventually lead to the so-called marine ice sheet instability. For the WAIS, where the bedrock lies below sea level and slopes down towards the interior of the ice sheet, MISI may lead to a (partial) collapse of this marine ice sheet. This process, first hypothesized in the 1970s, was recently theoretically confirmed and demonstrated in numerical models. It arises from thinning and eventually flotation of the ice near the grounding line, which moves the latter into deeper water where the ice is thicker. Thicker ice results in increased ice flux, which further thins (and eventually floats) the ice, resulting in further retreat into deeper water (and thicker ice) and so on
Pattyn, F., Ritz, C., Hanna, E. et al. (2018), The Greenland and Antarctic ice sheets under 1.5 °C global warming.20
Glacier meltwater at a glacier’s outlet acts a lid trapping warm ocean water at the base of the glacier. This meltwater freshens the ocean water, making it less dense, reducing ocean heat circulation to the surface, preventing this heat venting to the atmosphere and space.2122
As the ocean warms it begins to melt ice shelves, the tongues of ice that extend from the ice sheets into the ocean. These ice shelves buttress the land-based ice sheets. Thus as the ice shelves melt, the ice sheets expel ice into the ocean at a faster rate. This process is self-amplifying, because the melting icebergs freshen the ocean surface waters. Fresh water reduces the density of the ocean surface layer, thus reducing the ocean’s vertical overturning, which in turn reduces the release of ocean heat into the atmosphere and space. Instead, this ocean heat stays at depth, where it accelerates the rate of ice shelf melting.
The danger is that the ice discharge will pass a tipping point such that the amplifying feedbacks cause rapid acceleration of the melting process. It is even possible that, for a vulnerable portion of the Antarctic ice sheet sitting on bedrock well below sea level, the melting process could become self-sustaining. In that case, we say that a ‘point of no return’ is reached and it is too late to prevent discharge of massive amounts of ice, sufficient to raise sea level several meters. My colleagues and I estimate that this process could lead to multi-meter sea level rise in a period as short as 50 – 150 years, if greenhouse gases continue to increase rapidly.
If global warming continues unabated, portions of the ice sheets will become unstable, ice sheet disintegration will accelerate, and sea level will rise continuously. A majority of large U.S. and global cities are coastal. Continued high fossil fuel emissions will lead to eventual sea level rise that makes these cities dysfunctional, with consequences that are incalculable.
Hansen, 2018, Climate Change in a Nutshell: The Gathering Storm.23
Below Dr Hansen explains the amplifying feedbacks between the ocean and ice-sheets, in which he states: “These feedbacks raise questions about how soon we will pass points of no return and in which we lock in consequences that cannot be reversed on any time scale that people care about, consequences include sea level rise of several meters”:
current and future trends
Earth’s climate has alternated between ice ages and warm periods. Civilisation developed during the most recent warm period, known as the Holocene, that lasted 11,700 years. The prior warm period is known as the Eemian, between 130,000 to 115,000 years ago.25 The best estimate of the maximum temperature of the Eemian, relative to preindustrial time, is between +0.5℃ and +1.0℃.25 The global surface temperature averaged over 2014–2018 wrt 1850-1900 was +1.04℃ according to the WMO,26 and in 2019 wrt 1880-1920 was +1.2˚C according to NASA GISS (Goddard Institute for Space Studies) global temperature analysis (GISTEMP).27 Temperature data of the Holocene (smoothed over centennial time periods) does not exceed +0.5℃.28
We conclude that the modern trend line of global temperature crossed the early Holocene (smoothed) temperature maximum (+0.5℃) in about 1985.
Hansen et al. (2017), Young people’s burden: requirement of negative CO2 emissions.29
Therefore we have warmed our climate beyond the temperature range of the Holocene, and are about to warm it beyond that of the Eemian.
The Holocene, over 11,700 years in duration, had relatively stable climate, prior to the remarkable warming in the past half century. The Eemian, which lasted from about 130,000 to 115,000 years ago, was moderately warmer than the Holocene and experienced sea level rise to heights 6–9 m (20–30 ft) greater than today.
Hansen et al. (2017), Young people’s burden: requirement of negative CO2 emissions.28
Professor Eric Rignot explains below the mapping of glaciers on Greenland and Antarctica, how these glaciers are changing and the consequences of rapid multi-meter sea level rise that may soon occur as a result of 1.5℃ to 2℃ warming:
Pine Island, Thwaites, Haynes, Smith, Pope, and Kohler Glaciers are among the fastest-flowing glaciers in continental Antarctica. Combined together, they drain one third of the West Antarctic Ice Sheet into the Amundsen Sea Embayment (ASE). Their mass flux into the southern Pacific Ocean is comparable to that of the entire Greenland Ice Sheet into the Arctic Ocean. Since first revealed with satellite radar interferometry in the 1990s, this sector has been significantly out of balance due to glacier speedup. Concurrent with the acceleration in ice flow, the glaciers have been thinning and their grounding-line positions—where ice goes afloat—have been retreating at a rate of 1 km/yr, one of the fastest retreat rates in the world. Together, these glaciers and their catchment basins combined contain 1.2 m global sea level rise.
Observations of the ASE of West Antarctica since 1973 indicate speedup of all the glaciers and a steady increase in ice discharge into the ocean from the collective ensemble of these large, major glaciers. During retreat across their respective ice plains, Pine Island and Smith Glaciers underwent a rapid increase in ice discharge. However, since 2009, the ice discharge of Pine Island has remained steady. Thwaites Glacier, which had experienced a steady flow since 1992, started to speed up in 2006 and has increased its ice discharge considerably since.
Mouginot et al. (2014), Sustained increase in ice discharge from the Amundsen Sea Embayment, West Antarctica, from 1973 to 2013.31
The Antarctic lost 40 billion tons of melting ice to the ocean each year from 1979 to 1989. That figure rose to 252 billion tons lost per year beginning in 2009, according to a study published Monday in the Proceedings of the National Academy of Sciences. That means the region is losing six times as much ice as it was four decades ago, an unprecedented pace in the era of modern measurements. (It takes about 360 billion tons of ice to produce one millimeter of global sea-level rise.)
“I don’t want to be alarmist,” said Eric Rignot, an Earth-systems scientist for the University of California at Irvine and NASA who led the work. But he said the weaknesses that researchers have detected in East Antarctica — home to the largest ice sheet on the planet — deserve deeper study.
“The places undergoing changes in Antarctica are not limited to just a couple places,” Rignot said. “They seem to be more extensive than what we thought. That, to me, seems to be reason for concern.”
“The traditional view from many decades ago is that nothing much is happening in East Antarctica,” Rignot said, adding, “It’s a little bit like wishful thinking.”
The Washington Post, 2019, ‘Ice loss from Antarctica has sextupled since the 1970s, new research finds'33
East Antarctica has the potential to reshape coastlines around the world through sea level rise, but scientists have long considered it more stable than its neighbor, West Antarctica. Now, new detailed NASA maps of ice velocity and elevation show that a group of glaciers spanning one-eighth of East Antarctica’s coast have begun to lose ice over the past decade, hinting at widespread changes in the ocean.
“Totten is the biggest glacier in East Antarctica, so it attracts most of the research focus,” said Catherine Walker, a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who presented her findings at a press conference on Monday at the American Geophysical Union meeting in Washington. “But once you start asking what else is happening in this region, it turns out that other nearby glaciers are responding in a similar way to Totten.”
Walker found that four glaciers west of Totten, in an area called Vincennes Bay, have lowered their surface height by about 9 feet (almost 3 meters) since 2008—before that year, there had been no measured change in elevation for these glaciers. Farther east, a collection of glaciers along the Wilkes Land coast have approximately doubled their rate of lowering since around 2009, and their surface is now going down by about 0.8 feet (0.24 meters) every year.
“The change doesn’t seem random; it looks systematic,” said Alex Gardner, a glaciologist with NASA’s Jet Propulsion Laboratory in Pasadena, California.
“Those two groups of glaciers drain the two largest subglacial basins in East Antarctica, and both basins are grounded below sea level,” Walker said. “If warm water can get far enough back, it can progressively reach deeper and deeper ice. This would likely speed up glacier melt and acceleration, but we don’t know yet how fast that would happen. Still, that’s why people are looking at these glaciers, because if you start to see them picking up speed, that suggests that things are destabilizing.”
There is a lot of uncertainty about how a warming ocean might affect these glaciers, due to how little explored that remote area of East Antarctica is.
For example, if it turned out that the terrain beneath the glaciers sloped upward inland of the grounding line—the point where glaciers reach the ocean and begin floating over sea water, forming an ice shelf—and featured ridges that provided friction, this configuration would slow down the flow and loss of ice. This type of landscape would also limit the access of warm circumpolar deep ocean waters to the ice front.
A much worse scenario for ice loss would be if the bedrock under the glaciers sloped downward inland of the grounding line. In that case, the ice base would get deeper and deeper as the glacier retreated and, as ice calved off, the height of the ice face exposed to the ocean would increase. That would allow for more melt at the front of the glacier and also make the ice cliff more unstable, increasing the rate of iceberg release. This kind of terrain would make it easier for warm circumpolar deep water to reach the ice front, sustaining high melt rates near the grounding line.
NASA, 2018, More glaciers in East Antarctica are waking up.34
p. 54, box 1.1, M. R. Allen, O. P. Dube, W. Solecki, F. Aragón–Durand, W. Cramer, S. Humphreys, M. Kainuma, J. Kala, N. Mahowald, Y. Mulugetta, R. Perez, M. Wairiu, K. Zickfeld, 2018, Framing and Context. In: Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [V. Masson-Delmotte, P. Zhai, H. O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J. B. R. Matthews, Y. Chen, X. Zhou, M. I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, T. Waterfield (eds.)]. In Press.http://ipcc.ch/site/assets/uploads/sites/2/2018/11/SR15_Chapter1_Low_Res.pdf(↩)
Kopp, R. E., R. M. Horton, C. M. Little, J. X. Mitrovica, M. Oppenheimer, D. J. Rasmussen, B. H. Strauss, and C. Tebaldi (2014), Probabilistic 21st and 22nd century sea-level projections at a global network of tide-gauge sites, Earth’s Future, 2, 383–406, doi:10.1002/2014EF000239, https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014EF000239(↩)
table 2,1. p. 60, AR5 Synthesis Report – Climate Change 2014 IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp., https://www.ipcc.ch/report/ar5/syr/(↩)
p. 1174, section 18.104.22.168 and p. 1175 box 13.2, IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp. https://www.ipcc.ch/report/ar5/wg1/(↩)
Hansen, J., Sato, M., Hearty, P., Ruedy, R., Kelley, M., Masson-Delmotte, V., Russell, G., Tselioudis, G., Cao, J., Rignot, E., Velicogna, I., Tormey, B., Donovan, B., Kandiano, E., von Schuckmann, K., Kharecha, P., Legrande, A. N., Bauer, M., and Lo, K.-W.: Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous, Atmos. Chem. Phys., 16, 3761–3812, https://doi.org/10.5194/acp-16-3761-2016(↩)
Hansen, J., Sato, M., Kharecha, P., von Schuckmann, K., Beerling, D. J., Cao, J., Marcott, S., Masson-Delmotte, V., Prather, M. J., Rohling, E. J., Shakun, J., Smith, P., Lacis, A., Russell, G., and Ruedy, R.: Young people’s burden: requirement of negative CO2 emissions, Earth Syst. Dynam., 8, 577-616, https://doi.org/10.5194/esd-8-577-2017, 2017(↩)(↩)
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