Summary

Cumulative carbon dioxide (CO2) and nitrous oxide (N2O) solely determine our long-term heating commitment.1 2 The climate forcing of N2O is only about one tenth that of CO2, and N2O is changing slowly whereas CO2 is changing rapidly.3 Almost all CO2 emissions (83%) are due to our global energy system.4 5

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.6 The world’s coastal cities and ports would be flooded, devastating high population areas, and international trade and finance.

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.7 The best estimate of the global surface temperature of the Eemian, relative to preindustrial time, is between +1℃ and +1.5℃ (+1.8℉ to +2.7℉).7 The global surface temperature averaged over 2009–2018 was +0.93℃ relative to preindustrial time, and averaged over 2014–2018 was +1.04℃.8 9 Temperature data of the Holocene (smoothed over centennial time periods) does not exceed +0.5℃.

We conclude that the modern trend line of global temperature crossed the early Holocene (smoothed) temperature maximum (+0.5℃) in about 1985.

‘Young people’s burden: requirement of negative CO2 emissions, Hansen et al, 2017’.10

Therefore our climate has heated beyond the temperature range of the Holocene, and entered that 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?

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.

‘Young people’s burden: requirement of negative CO2 emissions, Hansen et al, 2017′11

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.

WMO, 2017, State of the Global Climate in 2017.12

Our CO2 emissions

The current global concentration of CO2 is over 410ppm.13 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.12

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.14 Half of all CO2 ever emitted has been emitted in the last 40 years and almost all by the world’s energy system.2 The most rapid increase of CO2 was caused during 2015, second fastest 2016, and 2018 tied with 1998 as the third fastest.2 15

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. Between the first joint scientific meeting in 1980, and 2019, CO2 emissions from fossil fuels and industry increased 90%, and increased 57% since COP1 in 1995.16 17 To make matters worse: (i) the sections below explain that limiting heating to 1.5℃ (the goal of the Paris Agreement) is not safe because when earth was last heated 1.5℃, seas were 6 to 9m (20 to 30ft) higher; (ii) the scale of emission reductions prescribed are beyond any historic precedent;18 (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;19 (v) 1.5℃ is imminent;20 and (vi) as explained below, carbon offsetting is spurious.

Carbon-offsets are spurious because:

  • Carbon-offset schemes have been proven to be a sham. They’re nothing more than marketing lies, unable to withstand scrutiny.21
  • 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’,22 the scale of carbon sinks made available for CDR should be maximised.

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 Hansen23 and colleagues. The most important finding of both is that it’s too late for decarbonisaton 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).

Negative emissions are a burden being imposed on young people.

Hansen, Young people’s burden: requirement of negative CO2 emissions.24

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.

Net zero emissions concept. IPCC. 2018. Understanding the IPCC Special Report on 1.5°C.25

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.

p. 1, Rockström, J. et al. (2016), The world’s biggest gamble.26

The IPCC’s 1.5℃ scenarios demand that CO2 emissions are halved by 2030,27 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.28 These scenarios have only a 50% to 66% chance of success29 and large uncertainties remain concerning the feasibility and impact of large-scale deployment of negative emission technologies.30

Dr James Hansen23 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.31 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.

What time remains?

We have no choice but to adhere to a carbon dioxide (CO2) budget, because cumulative CO2 solely determines our long-term warming commitment, and we have an obligation to minimise a future burden of negative emissions. Our rate of CO2 emissions determines how much time remains to stay within budget, and the following paragraphs make it obvious that technology can only play a limited role in the short term, and that social measures are required, such as pricing and rationing of carbon.

The IPCC’s SR15 identified a large number of mitigation studies in the literature that explored 1.5°C-consistent pathways.32 The pathways were classified as shown below.

The supporting material for SR15 lists the CO2 budget for each pathway classification remaining from 1/1/2018.33 (projections for non-CO2 greenhouse gases are also included in the pathways).34

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.35

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 2019.36

The CO2 budgets remaining from 1/1/2020 are listed below, calculated by subtracting the annual emissions for years 2018 and 2019 away from the IPCC’s budgets referenced above. Also included are the range of budgets remaining due to uncertainties,37 with half of the total uncertainty applied in either direction; half because it would be unexpected for each of the uncertainties to all be at one extreme.

The world’s energy system remains intensively fossil fuelled, emission offsets are spurious to avoid adequate action now, and there is no time left for half-measures; “Winning slowly is the same as losing.”38

  1. Matthews, H.D., Gillett, N.P., Stott, P.A. and Zickfeld, K., 2009. The proportionality of global warming to cumulative carbon emissions. Nature459(7248), p.829.()
  2. https://www.worldenergydata.org/ghgs/()()()
  3. Charts 1 and 3, https://www.worldenergydata.org/ghgs/()
  4. 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’.()
  5. Calculations: (1) 2017: Total emissions = fossil and cement emissions + land-use change emissions = 35.84 + 5.39 = 41.23 GtCO₂. Fossil fuel plus flaring emissions = (14.49 + 12.28 + 7.11 + 0.34) / 41.23 = 83%. (2) 2018: Total emissions = fossil and cement emissions + land-use change emissions = 36.60 + 5.53 = 42.13 GtCO₂. Fossil fuel plus flaring emissions = (14.69 + 12.43 + 7.49 + 0.34)/42.13 = 83%.()
  6. See section titled ‘Sea level rise’, https://www.worldenergydata.org/existential-threat-pt1/()
  7. 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()()
  8. p6, https://library.wmo.int/doc_num.php?explnum_id=5789()
  9. 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.()
  10. p 581, 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()
  11. p. 580-581, 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()
  12. WMO Statement on the State of the Global Climate in 2017()()
  13. https://www.esrl.noaa.gov/gmd/ccgg/trends/global.html()
  14. https://www.worldenergydata.org/ghgs//()
  15. https://www.esrl.noaa.gov/gmd/ccgg/trends/gl_gr.html()
  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%()
  17. 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’. Value for 2019 is projection shown in Global Carbon Budget, https://www.globalcarbonproject.org/carbonbudget/19/files/GCP_CarbonBudget_2019.pdf()
  18. p.16, C.2.1, https://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdf()
  19. chart 7, https://www.worldenergydata.org/ghgs/()
  20. https://www.theguardian.com/environment/planet-oz/2017/may/09/planet-could-breach-15c-warming-limit-within-10-years-but-be-aware-of-caveats()
  21. https://www.mirror.co.uk/news/uk-news/licence-pollute-sham-carbon-offsetting-20873564.amp()
  22. 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.()
  23. http://www.columbia.edu/~jeh1/()()
  24. https://www.earth-syst-dynam.net/8/577/2017/()
  25. https://library.wmo.int/doc_num.php?explnum_id=5188()
  26. Rockström, J. et al. (2016), The world’s biggest gamble, Earth’s Future, 4, 465 – 470, doi:10.1002/2016EF000392.()
  27. chart 3, https://www.worldenergydata.org/1-5c/()
  28. chart 6, https://www.worldenergydata.org/1-5c/()
  29. table 1, https://www.worldenergydata.org/1-5c/()
  30. 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.()
  31. https://www.worldenergydata.org/350ppm/()
  32. p. 99, chap. 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/()
  33. table 2.SM.12, p2A-28, https://www.ipcc.ch/report/sr15/chapter-2-supplementary-materials/()
  34. fig 2.6 and 2.7, 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/()
  35. https://www.carbonbrief.org/analysis-fossil-fuel-emissions-in-2018-increasing-at-fastest-rate-for-seven-years()
  36. https://www.carbonbrief.org/guest-post-a-new-approach-for-understanding-the-remaining-carbon-budget()
  37. 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/()
  38. https://www.rollingstone.com/politics/politics-news/bill-mckibben-winning-slowly-is-the-same-as-losing-198205/()