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Earth System Dynamics An interactive open-access journal of the European Geosciences Union

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Earth Syst. Dynam., 8, 577-616, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
18 Jul 2017
Young people's burden: requirement of negative CO2 emissions
James Hansen1, Makiko Sato1, Pushker Kharecha1, Karina von Schuckmann2, David J. Beerling3, Junji Cao4, Shaun Marcott5, Valerie Masson-Delmotte6, Michael J. Prather7, Eelco J. Rohling8,9, Jeremy Shakun10, Pete Smith11, Andrew Lacis12, Gary Russell12, and Reto Ruedy12,13 1Climate Science, Awareness and Solutions, Columbia University Earth Institute, New York, NY 10115, USA
2Mercator Ocean, 10 Rue Hermes, 31520 Ramonville St Agne, France
3Leverhulme Centre for Climate Change Mitigation, University of Sheffield, Sheffield, S10 2TN, UK
4Key Lab of Aerosol Chemistry and Physics, SKLLQG, Institute of Earth Environment, Xi'an, 710061, China
5Department of Geoscience, 1215 W. Dayton St., Weeks Hall, University of Wisconsin-Madison, Madison, WI 53706, USA
6Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l'Environnement (CEA-CNRS-UVSQ) Université Paris Saclay, Gif-sur-Yvette, France
7Earth System Science Department, University of California at Irvine, CA, USA
8Research School of Earth Sciences, The Australian National University, Canberra, 2601, Australia
9Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, SO14 3ZH, UK
10Department of Earth and Environmental Sciences, Boston College, Chestnut Hill, MA 02467, USA
11Institute of Biological and Environmental Sciences, University of Aberdeen, 23 St Machar Drive, Aberdeen, AB24 3UU, UK
12NASA Goddard Institute for Space Studies, New York, NY 10025, USA
13SciSpace LLC, 2880 Broadway, New York, NY 10025, USA
Abstract. Global temperature is a fundamental climate metric highly correlated with sea level, which implies that keeping shorelines near their present location requires keeping global temperature within or close to its preindustrial Holocene range. However, global temperature excluding short-term variability now exceeds +1 °C relative to the 1880–1920 mean and annual 2016 global temperature was almost +1.3 °C. We show that global temperature has risen well out of the Holocene range and Earth is now as warm as it was during the prior (Eemian) interglacial period, when sea level reached 6–9 m higher than today. Further, Earth is out of energy balance with present atmospheric composition, implying that more warming is in the pipeline, and we show that the growth rate of greenhouse gas climate forcing has accelerated markedly in the past decade. The rapidity of ice sheet and sea level response to global temperature is difficult to predict, but is dependent on the magnitude of warming. Targets for limiting global warming thus, at minimum, should aim to avoid leaving global temperature at Eemian or higher levels for centuries. Such targets now require negative emissions, i.e., extraction of CO2 from the air. If phasedown of fossil fuel emissions begins soon, improved agricultural and forestry practices, including reforestation and steps to improve soil fertility and increase its carbon content, may provide much of the necessary CO2 extraction. In that case, the magnitude and duration of global temperature excursion above the natural range of the current interglacial (Holocene) could be limited and irreversible climate impacts could be minimized. In contrast, continued high fossil fuel emissions today place a burden on young people to undertake massive technological CO2 extraction if they are to limit climate change and its consequences. Proposed methods of extraction such as bioenergy with carbon capture and storage (BECCS) or air capture of CO2 have minimal estimated costs of USD 89–535 trillion this century and also have large risks and uncertain feasibility. Continued high fossil fuel emissions unarguably sentences young people to either a massive, implausible cleanup or growing deleterious climate impacts or both.

Citation: 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,, 2017.
Publications Copernicus
Short summary
Global temperature now exceeds +1.25 °C relative to 1880–1920, similar to warmth of the Eemian period. Keeping warming less than 1.5 °C or CO2 below 350 ppm now requires extraction of CO2 from the air. If rapid phaseout of fossil fuel emissions begins soon, most extraction can be via improved agricultural and forestry practices. In contrast, continued high emissions places a burden on young people of massive technological CO2 extraction with large risks, high costs and uncertain feasibility.
Global temperature now exceeds +1.25 °C relative to 1880–1920, similar to warmth of the Eemian...