Tuesday, November 02, 2021

A Prediction We Will Get to Test

Climate change may affect the production of maize (corn) and wheat as early as 2030 under a high greenhouse gas emissions scenario, according to a new NASA study published in the journal, Nature Food. Maize crop yields are projected to decline 24%, while wheat could potentially see growth of about 17%. (Source)

Most projected effects of climate change are far enough in the future so that the people who made and trumpeted them will be dead, or at least retired, well before we see if they are true, but this one is only nine years in the future. If, as I expect, it turns out to be false, if world maize output continues to grow as it has been doing for a very long time, I plan to announce the fact here — and nobody will notice. 

As an example of how the wording of a news story reflects the biases of the author, note that the decline in maize is "projected" while wheat "could potentially see growth." Both are projections from the same source but the positive one is put in more uncertain terms than the negative.

Following the link to the abstract, I note that:

Mean end-of-century maize productivity is shifted from +5% to −6% (SSP126) and from +1% to −24% (SSP585)—explained by warmer climate projections and improved crop model sensitivities. In contrast, wheat shows stronger gains (+9% shifted to +18%, SSP585), linked to higher CO2 concentrations and expanded high-latitude gains. 

Can any reader point me to news articles or a NASA web page from the previous round of the research trumpeting the fact that both maize and wheat productivity were projected to increase due to climate change? 

I also noticed:

Higher levels of carbon dioxide in the atmosphere have a positive effect on photosynthesis and water retention, increasing crop yields, though often at a cost to nutrition.

Assuming their source is the same one I discussed in an old blog post, "cost to nutrition" means that CO2 fertilization increases yield in calories by more than it increases yield in some other nutrients — two out of ten minerals in wheat, for example — hence lowers the amount of those nutrients per calorie.