Dangerous human-made interference with climate: a GISS modelE study
Résumé
We investigate the issue of "dangerous humanmade 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 2σ (standard deviations) of 20th century variability, but other scenarios yield regional changes of 5-10σ , 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,
| Origine | Fichiers éditeurs autorisés sur une archive ouverte |
|---|