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1 GISS - NASA Goddard Institute for Space Studies 2 Columbia University Earth Institute 3 Sigma Space Partners LLC 4 Department of Earth and Environmental Sciences 5 APAM - Department of Applied Physics and Applied Mathematics 6 CATF - Clean Air Task Force 7 GSFC - NASA Goddard Space Flight Center 8 LSCE - Laboratoire des Sciences du Climat et de l-Environnement Gif-sur-Yvette

Abstract : 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-m2 in 2100, keeps further global warming under 1°C if climate sensitivity is ~3°C or less for doubled CO2. 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 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 O3, its precursor CH4, and soot as by CO2, offering hope that dual efforts to reduce pollutants and slow CO2 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-CO2 forcings has slowed in recent years, but CO2 emissions are now surging well above the alternative scenario. Prompt actions to slow CO2 emissions and decrease non-CO2 forcings are needed to achieve the low forcing of the alternative scenario.





Autor: J. Hansen - M. Sato - R. Ruedy - P. Kharecha - A. Lacis - R. Miller - L. Nazarenko - K. Lo - G. A. Schmidt - G. Russell - I. Alei

Fuente: https://hal.archives-ouvertes.fr/



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