This short page hopes to summarise why and how we must change for a chance of a safe climate. Other pages listed in the Climate Crisis menu above discuss this in greater detail.
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.3
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.4
Our greatest threat
While climate change is causing more frequent and severe harmful impacts, multi-metre sea level rise would be irreversible and leave global civilisation ungovernable.5 The world’s coastal cities and ports would be flooded, devastating high population areas, and international trade and finance.
In the past, Earth’s climate alternated between ice ages and warm periods. Civilisation developed during the warm period known as the Holocene. The prior warm period is known as the Eemian, which lasted from 130,000 to 115,000 years ago.6 The best estimate of the maximum global surface temperature of the Eemian, relative to preindustrial time, is between +1℃ and +1.5℃ (+1.8℉ to +2.7℉).6 The global surface temperature averaged over 2009 to 2018 was +0.9℃ relative to preindustrial time, and +1℃ over 2014 to 2018.7 8 Therefore global heating will soon exceed our maximum estimate of the maximum temperature of the Eemian. We have left the safe temperature range of the Holocene, and are about to leave the temperature range of the Eemian.
During the Eemian, seas were 6 to 9 metres (20 to 30 feet) higher than today, so rapid multi-metre sea level rise is expected if the global heating isn’t reduced. This would result from the collapse of Earth’s ice sheets, of which there are three – the Greenland, West Antarctic and East Antarctic ice sheets. Therefore the principal question is not how much sea level rise, but how fast?
Our CO2 emissions
The current global concentration of CO2 is over 410ppm.9 The last time Earth’s atmosphere contained this was during the mid-Pliocene, 3 to 5 million years ago when the seas were 10 to 20 metres (33 to 66 feet) higher than today.10
Our CO2 emissions solely determine our planet’s long term average surface temperature, are the only rapidly increasing greenhouse gas, and continue to grow with no peak in sight.11 Half of all CO2 ever emitted has been emitted in the last 40 years and almost all by the world’s energy system.11 The most rapid increase of CO2 was caused during 2015, second fastest 2016, and 2018 tied with 1998 as the third fastest.11 12
Now in late 2019, 4 years after the Paris Agreement, 25 years since the UNFCCC came into force, 31 years since the formation of the IPCC, and 39 years since the first joint scientific meeting about atmospheric CO2, NOTHING has been achieved except to INCREASE CO2 emissions. CO2 emissions, in 2018, from fossil fuels and industry have increased by 91% since the first joint scientific meeting in 1980, and increased 61% since 1995 when COP1 took place.13 To make matters worse: (i) the sections below explain that limiting warming to 1.5℃ (the goal of the Paris Agreement) is not safe, (ii) the scale of emission reductions prescribed are beyond any historic precedent,14 (iii) prescribed emission reductions depend on concurrent massive CO2 removal, (see chart 10 on this page) (iv) the annual increase of CO2 emissions is near record rate,15 and (v) 1.5℃ is imminent.16
What to do?
Two prominent efforts have pursued solutions: the UN’s climate treaty relying on the science of the IPCC, and the efforts of Dr James Hansen17 and colleagues. The most important finding of both is that it’s too late for emission reductions alone, and now ‘negative emission technologies’ (NETs), also known as ‘carbon dioxide removal’ (CDR) methods, are also required (this includes measures to increase natural carbon sinks such as reforestation).
To stabilise temperature, CO2 emissions need to be made net-zero as shown below. This can only be achieved by rapidly reducing CO2 emissions (i.e. decarbonising) to the lowest level possible, and by using negative emissions. The faster emissions are reduced, the smaller the burden of negative emissions.
The IPCC’s 1.5℃ scenarios demand that CO2 emissions are halved by 2030,21 and over the next 30 years negative emissions are ramped up so that by 2050, an amount of CO2 will have been removed from the atmosphere equivalent to that removed by the world’s ocean over a period of 15 years (about 150GtCO2). By around 2050, this additional carbon-sink will need to be so vast that it will annually remove an amount of CO2 equivalent to that removed annually by the global ocean.22 These scenarios have only a 50% to 66% chance of success23 and large uncertainties remain concerning the feasibility and impact of large-scale deployment of negative emission technologies.24
Regarding negative emissions, the concept of a carbon-offset to offset a carbon intensive activity is a falsehood for the following reasons:
- Any such offset, if credible, should be implemented now to help mitigate existing climate impacts, not instead used to clear the conscience of one indulging in a carbon-intensive activity,
- Economies cannot be completely decarbonised, so countries will need to increase their natural carbon sinks to compensate, leaving no surplus to be used as a supposed carbon-offset.
- Given that ‘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’,25 the scale of carbon sinks made available for CDR should be maximised.
- Modelled emission pathways attribute only a low 66% chance of limiting warming to 1.5°C. The sooner and faster we decarbonise, and the greater the size of natural carbon sinks, the greater our chance to limit warming and minimise the size of the negative emissions burden. Carbon-offsets are contrary to this.
Dr James Hansen17 prescribes changes needed to reduce atmospheric CO2 to less than 350ppm, in order to limit global temperature close to the Holocene range of +1℃ maximum. CO2 emissions must be reduced by one third by 2030 and the negative emissions burden is the same as that prescribed by the IPCC above.26 Despite decarbonisation being slower than that prescribed by the IPCC, Hansen’s modelling results in warming being limited to less than +1°C, so hopefully preventing multi-metre sea level rise.
The world’s energy system remains intensively fossil fuelled, emission offsets are a lie to avoid adequate action now, and there is no time left for half-measures; “Winning slowly is the same as losing.”27
- Matthews, H.D., Gillett, N.P., Stott, P.A. and Zickfeld, K., 2009. The proportionality of global warming to cumulative carbon emissions. Nature, 459(7248), p.829.
- Calculations: (1) 2016: Total emissions = (9.74 + 1.3) = 11.04 GtC. Fossil fuel plus flaring emissions = (3.95 + 3.4 + 1.92 + .068) / 11.04 = 84.6%. (2) 2017: Total emissions = (9.87 + 1.39) = 11.26 GtC. Fossil fuel plus flaring emissions = (3.98 + 3.45 + 1.97 + .068) / 11.26 = 84.1%. Emissions from fossil fuel combustion and cement production: Boden, T. A., Marland, G., and Andres, R. J.: Global, Regional, and National Fossil-Fuel CO2 Emissions, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A., doi 10.3334/CDIAC/00001_V2017, 2017. Data available at https://www.icos-cp.eu/GCP/2018, download labelled ‘2018 Global Budget v1.0’. Emissions from land-use change average of two bookkeeping models: Houghton, R. A. and Nassikas, A. A.: Global and regional fluxes of carbon from land use and land cover change 1850-2015, Global Biogeochemical Cycles, 31, 456-472, 2017; Hansis, E., Davis, S. J., and Pongratz, J.: Relevance of methodological choices for accounting of land use change carbon fluxes, Global Biogeochemical Cycles, 29, 1230-1246, 2015. Data available at https://www.icos-cp.eu/GCP/2018, download labelled ‘2018 Global Budget v1.0’.
- See section titled ‘Sea level rise’, https://www.worldenergydata.org/climate-part-2/
- 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
- p6, https://library.wmo.int/doc_num.php?explnum_id=5789
- The previous two references use slightly different definitions for preindustrial. Hansen uses 1880 – 1920 and the WMO uses 1850 – 1900. The difference in temperature of these two periods is negligible in the context here.
- WMO Statement on the State of the Global Climate in 2017
- CO2 emissions from fossil fuel combustion and cement: (i) in 1980 = 5.29GtC = 5.29*44/12GtCO2 = 19.4GtCO2; (ii) in 1995 = 6.28GtC = 23.03GtCO2; and (iii) in 2018 = 37.1GtCO2. 2018 with respect to 1980 = 37.1/19.4 = +91%, and 2018 with respect to 1995 = 37.1/23.03 = +61%. Values for 1980 and 1995 from Emissions from fossil fuel combustion and cement production: Boden, T. A., Marland, G., and Andres, R. J.: Global, Regional, and National Fossil-Fuel CO2 Emissions, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A., doi 10.3334/CDIAC/00001_V2017, 2017, https://www.icos-cp.eu/GCP/2018, download labelled ‘2018 Global Budget v1.0’. Value for 2018 is projection shown in Global Carbon Budget, https://www.globalcarbonproject.org/carbonbudget/18/files/GCP_CarbonBudget_2018.pdf
- p.16, C.2.1, https://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdf
- chart 3 in Part 1
- chart 7, https://www.worldenergydata.org/climate-part-3/
- chart 10, https://www.worldenergydata.org/climate-part-3/
- table 1, https://www.worldenergydata.org/climate-part-3/
- p. 121, 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.
- 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.
- section titled ‘350 ppm’, https://www.worldenergydata.org/climate-part-3/