Thursday, February 17, 2011

Heat Shock

Since the political party that worries about global warming is also the one that is likely to try and take our guns away, global warming is not a popular scenario with survivalists.  IMO that is a mistake.  When you look at the less partisan sources out there it is very much an issue of concern.  Arguing that it is all a lie because it is cold in Texas (in February) while ignoring that it has been extremely warm in Washington DC (for February) is just not going to get us anywhere.

Another issue is:  so what?  Why should I care if it gets a little warmer?  Well today's post is along the lines of showing why it might be very much an issue.

When listening to a talk by Professor Homer-Dixon, he commented on a recent article on the problems likely to be faced in crop yields because of global warming.

He was referring to  David. S. Battisti1 and Rosamond L. Naylors' Historical Warnings of Future Food Insecurity with Unprecedented Seasonal Heat.  I have chopped it up a bit, but here are some of the points they made:

We calculated the difference between projected and historical seasonally averaged temperatures throughout the world by using output from the 23 global climate models contributing to the Intergovernmental Panel on Climate Change’s (IPCC) 2007 scientific synthesis. Our results show that it is highly likely (greater than 90% chance) that growing season temperatures by the end of the 21st century will exceed even the most extreme seasonal temperatures recorded from 1900 to 2006 for most of the tropics and subtropics.
Although much attention is focused on threats of increased droughts in subtropical agriculture, the potential impacts of seasonal average temperature changes in both the tropics and subtropics, which are expected to be large relative to the historical range of variation, are often overlooked. Experimental and crop-based models for major grains in these regions show direct yield losses in the range of 2.5 to 16% for every 1°C increase in seasonal temperature.
Despite the general perception that agriculture in temperate latitudes will benefit from increased seasonal heat and supply food to deficit areas, even mid-latitude crops will likely suffer at very high temperatures in the absence of adaptation.
Severe heat in the summer of 2003 affected food production as well as human lives in Europe. Record high daytime and nighttime temperatures over most of the summer growing season reduced leaf and grain-filling development of key crops such as maize, fruit trees, and vineyards; accelerated crop ripening and maturity by 10 to 20 days; caused livestock to be stressed; and resulted in reduced soil moisture and increased water consumption in agriculture. Italy experienced a record drop in maize yields of 36% from a year earlier, whereas in France maize and fodder production fell by 30%, fruit harvests declined by 25%, and wheat harvests (which had nearly reached maturity by the time the heat set in) declined by 21%.

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