Michael Tobis wrote: > This is not accidental. If, under global warming, the fortunes of > Canada improve and the fortunes of India decline, the net effect > area-weighted might be for increased biomass, but the net effect on > human well-being will be highly negative. To a very significant > extent, this is because India is more hospitable than Canada. This is > at least one reason why the former is overcrowded and the latter > largely uninhabited.
This, I think, allows be to introduce an egregious (but all too typical) bit of cherry picking - or should I call it rotten apple picking - in the news today. The UNDP's new "Human Development Report" is out, and on the BBC: http://news.bbc.co.uk/1/low/sci/tech/6126242.stm you can see the reproduced graphic which paints a picture of reduced crop yields in Africa, along with the title "Projected impact of climate change on cereal productivity in Africa." Substantial areas show large drops of 25% or more "by 2080". Going back to the UNDP report, this map is found to be based on a paper in which some researchers took climates from a range of models under all the main SRES marker scenarios, which give quite a range of results when fed into their crop model. I guess I don't need to tell you which set of model results (both from least to most alarming model, and least to most alarming scenario) are used for the graphic which the UNDP selected, and from which they quote results. The authors of the paper even clearly emphasise (at least twice) that the A2 scenario is now considered very much an outlier in terms of what is actually plausible. There wasn't room to mention that minor detail in the 424 pages of the UNDP report, of course. So far, so standard. But on top of that, the authors of the paper also point out that none of these potential yield losses in any region actually approach the amount by which the current yield actually undershoots the potential. That presumably means that take-up of normal farming practice would mean increased yields even in the worst affected areas and under the hypothesis of extremely high emissions and the worst set of model results. There's not even a need to appeal to out-of-thin-air technological miracles here, although technological advances would hardly be unexpected over this time scale. Surely the appropriate response here is for these societies to develop and modernise, which will bring rapid and substantial benefits across a broad swathe of problems, rather than "climate-proof" themselves against something that might in extremis have a modest effect many decades hence if they haven't moved on in the meantime. Incidentally, according to the paper, the reduction in yield and accompanying increase in hunger should be roughly linear with time/CO2 concentration, which suggests that it should perhaps be visible by now if it is a real effect (I don't know about interannual variability or quality of data collection though). Anyone know if there are data supporting this? James --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
