A couple of years ago, I took a look at the FAO data for global cereal yields with a view to answering the question of whether climate change was yet having a noticeable impact on global food production. At that time, the answer was unequivocally no:
So, clearly, the overwhelming story in global agricultural yields is this: improving agricultural technology has increased yields at a steady, reliable pace - they have more than doubled over the last 50 years. There just is absolutely no support in the data for the idea that climate change, or any other negative or scary factor you care to name - eroding soil, depleting aquifers, peaking oil supplies - is causing the agricultural yield curve to start bending downward. Maybe they will in the future, but it sure isn't happening yet.At that time, the slope of the straight line through the yield data was 0.0442 tonnes/hectare/year. The straight line explained 99.132% of the variance in the data, and a quadratic, which could potentially capture the data bending downward, only explained an additional 0.016% of the data.
So has two additional years worth of data (2010-2011) changed the picture?
No, it hasn't. 2011 was the highest yield yet, the slope of the line has increased to 0.0446 tonnes/hectare/year, it now explains 99.153% of the variance in the data, and the quadratic is down to explaining only an additional 0.001% of the variance (yes, the straight line is good to four significant figures).
I also looked at the departures from the straight line, as a percentage of the yield, to see if relative fluctuations in the total harvest were increasing. The answer, then as now, is no:
Fluctuations, relative to the current yield level, are going down over time.
Climate change is scary, we are clearly melting the north pole, droughts and floods and heat waves are increasing over time. However, so far, it's not hitting us where it would really hurt: in the stomach.