Suppose for the moment that the "urban heat island" effect has in fact been massively underestimated, eg because there's a systematic change in the local surroundings of even "rural" stations (eg much more local asphalt) that's somehow missed scientists' attention,
and actual temperature increase since pre-industrial isn't 0.7 +/- 0.2 C, but only 0.3C, would that in any way contradict the rest of global warming science? After all, the span given by IPCC for current net anthropogenic forcing is huge http://www.ipcc.ch/SPM2feb07.pdf Namely 0.6 to 2.4 W/m2. Say we are at the low end of that range, say 0.8 W/m2, then a climate sensitivity of 3C and thermal lag might only give us 0.3C. Conversely, suppose that there's actually a so far overlooked cooling artifact in the data (say much more shaded stations) and actual temperature increase is already 1.2C, again there's no contradiction with the forcing span, as 2 W/m2 and 3C climate sensitivity might explain the increase. And how much does this really matter for predictions? Climate sensitivity isn't constrained primarily by the 20th century temperature/forcing record, and most of the uncertainty for the forcing is from aerosols. As long as the latter decline in relative importance, the temperature prediction for doubled CO2 (and zero aerosols) would be 3C no matter whether temperature has risen 0.3 or 1.2C to date? --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/globalchange -~----------~----~----~----~------~----~------~--~---
