¹ http://unfccc.int/essential_background/glossary/items/3666.php

² And other GHG, but see Fig. 13.1: the forcing from CO2 is by far the dominant forcing.

³ This may change if various geo-engineering approaches come to play a significant role in the management of the climate change problem (Crutzen, 2006; Keith, 2001). For a review of these possibilities, see Keith (2007). Though preliminary analysis suggests the idea of attempting to tune global mean temperatures by lowering insolation might ought not be dismissed out ofhand (Govindasamy and Caldeira, 2000), more full analyses are required before this becomes a serious policy option(Kiehl, 2006). Inany case, some problems of the direct effects of carbon – such as ocean acidification – are likely to remain significant issues, inviting the pessimistic possibility that geoengineering may carry its own severe climate-related risks.