Dangerous human-made interference with climate: a GISS modelE study

• Published in: Climate Dynamics
• Main Authors: Hansen, J., Sato, M., Ruedy, R., Kharecha, P., Lacis, A., Miller, R., Nazarenko, L., Lo, K., Schmidt, G. A., Russell, G., Aleinov, I., Bauer, S., Baum, E., Cairns, B., Canuto, V., Chandler, M., Cheng, Y., Cohen, A., del Genio, A., Faluvegi, G., Fleming, E., Friend, A., Hall, T., Jackman, C., Jonas, J., Kelley, M., Kiang, N. Y., Koch, D., Labow, G., Lerner, J., Menon, S., Novakov, T., Oinas, V., Perlwitz, Ja., Perlwitz, Ju., Rind, D., Romanou, A., Schmunk, R., Shindell, D., Stone, P., Sun, S., Streets, D., Tausnev, N., Thresher, D., Unger, N., Yao, M., Zhang, S.
• Other Authors: NASA Goddard Institute for Space Studies (GISS), NASA Goddard Space Flight Center (GSFC), Columbia University Earth Institute, Columbia University New York, Sigma Space Partners LLC, Department of Earth and Environmental Sciences New York, Department of Applied Physics and Applied Mathematics New York (APAM), Clean Air Task Force (CATF), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Department of Geology, Yale University New Haven, Lawrence Berkeley National Laboratory Berkeley (LBNL), Massachusetts Institute of Technology (MIT), Argonne National Laboratory Lemont (ANL)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2007
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Arctic; Climate change; Global warming; Ice Sheet; Ice Shelves
• Online Access: https://hal.science/hal-00328500; https://hal.science/hal-00328500/document; https://hal.science/hal-00328500/file/acp-7-2287-2007.pdf; https://doi.org/10.1007/s00382-007-0255-8

International audience We investigate the issue of "dangerous human-made interference with climate" using simulations with GISS modelE driven by measured or estimated forcings for 1880–2003 and extended to 2100 for IPCC greenhouse gas scenarios as well as the "alternative" scenario of Hansen and Sato (2004). Identification of "dangerous" effects is partly subjective, but we find evidence that added global warming of more than 1°C above the level in 2000 has effects that may be highly disruptive. The alternative scenario, with peak added forcing ~1.5 W/m 2 in 2100, keeps further global warming under 1°C if climate sensitivity is ~3°C or less for doubled CO 2 . The alternative scenario keeps mean regional seasonal warming within 2s (standard deviations) of 20th century variability, but other scenarios yield regional changes of 5–10s, i.e. mean conditions outside the range of local experience. We conclude that a CO 2 level exceeding about 450 ppm is "dangerous", but reduction of non-CO 2 forcings can provide modest relief on the CO 2 constraint. We discuss three specific sub-global topics: Arctic climate change, tropical storm intensification, and ice sheet stability. We suggest that Arctic climate change has been driven as much by pollutants (O 3 , its precursor CH 4 , and soot) as by CO 2 , offering hope that dual efforts to reduce pollutants and slow CO 2 growth could minimize Arctic change. Simulated recent ocean warming in the region of Atlantic hurricane formation is comparable to observations, suggesting that greenhouse gases (GHGs) may have contributed to a trend toward greater hurricane intensities. Increasing GHGs cause significant warming in our model in submarine regions of ice shelves and shallow methane hydrates, raising concern about the potential for accelerating sea level rise and future positive feedback from methane release. Growth of non-CO 2 forcings has slowed in recent years, but CO 2 emissions are now surging well above the alternative scenario. Prompt actions to slow CO 2 emissions and ...