We had an interesting chat a couple of weeks ago about the way the noble Lord Stern had portrayed the effects on climate change on wheat yields. However, alongside his wheat graph is another graph portraying a similar effect of raised temperatures on ground nuts (click for full size).
;)
The cited paper, Vara Prasad et al (2001), is not online, but the abstract is here. Unlike the wheat paper, Vara Prasad appears to look only at the effects of temperature on groundnuts and Stern's graph seems to reflect the abstract pretty much exactly.
One question that occurs to me, based on the abstract, relates to the temperatures applied to the plants. Apparently, elevated temperatures were applied during the daytime. Of course, temperatures are not constant over the course of a day - they start and end the day much lower than the midday maximum. I wonder therefore whether the experiment was realistic to the extent that it reflected some kind of a daily temperature profile. Presumably the effect of hitting temperatures of say 38°C for a couple of hours in the middle of the day is different to a 12-hour baking at that temperature. Without seeing the full paper it's hard to reach a conclusion.
Despite the Vara Prasad paper not looking at the effects of CO2 on peanuts, this is still a question that is worth examining. Fortunately, there is the excellent CO2Science website, which collates the results of studies into this question.
Here's the page for peanuts.
|
300 ppm
|
600 ppm
|
900 ppm
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|
| Number of results |
38
|
|
1
|
| Arithmetic mean |
60.3%
|
|
35%
|
| Standard error |
16.1%
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|
0%
|
It looks as though there is a very strong compensatory effect from carbon dioxide fertilisation.