Global warming in the pipeline
Abstract
Improved knowledge of glacial-to-interglacial global temperature change implies that fast-feedback equilibrium climate sensitivity (ECS) is 1.2 +/- 0.3{\deg}C (2) per W/m. Consistent analysis of temperature over the full Cenozoic era -- including "slow" feedbacks by ice sheets and trace gases -- supports this ECS and implies that CO was about 300 ppm in the Pliocene and 400 ppm at transition to a nearly ice-free planet, thus exposing unrealistic lethargy of ice sheet models. Equilibrium global warming including slow feedbacks for today's human-made greenhouse gas (GHG) climate forcing (4.1 W/m) is 10{\deg}C, reduced to 8{\deg}C by today's aerosols. Decline of aerosol emissions since 2010 should increase the 1970-2010 global warming rate of 0.18{\deg}C per decade to a post-2010 rate of at least 0.27{\deg}C per decade. Under the current geopolitical approach to GHG emissions, global warming will likely pierce the 1.5{\deg}C ceiling in the 2020s and 2{\deg}C before 2050. Impacts on people and nature will accelerate as global warming pumps up hydrologic extremes. The enormity of consequences demands a return to Holocene-level global temperature. Required actions include: 1) a global increasing price on GHG emissions, 2) East-West cooperation in a way that accommodates developing world needs, and 3) intervention with Earth's radiation imbalance to phase down today's massive human-made "geo-transformation" of Earth's climate. These changes will not happen with the current geopolitical approach, but current political crises present an opportunity for reset, especially if young people can grasp their situation.
Keywords
Cite
@article{arxiv.2212.04474,
title = {Global warming in the pipeline},
author = {James E. Hansen and Makiko Sato and Leon Simons and Larissa S. Nazarenko and Isabelle Sangha and Karina von Schuckmann and Norman G. Loeb and Matthew B. Osman and Qinjian Jin and Pushker Kharecha and George Tselioudis and Eunbi Jeong and Andrew Lacis and Reto Ruedy and Gary Russell and Junji Cao and Jing Li},
journal= {arXiv preprint arXiv:2212.04474},
year = {2023}
}
Comments
62 pages, 39 figures, 1 table. Revision for journal resubmission