It has become pretty common to hear otherwise well informed left-leaning observers claim that climate change is affecting food production. Krugman said the other week
Why is production down? Most of the decline in world wheat production, and about half of the total decline in grain production, has taken place in the former Soviet Union — mainly Russia, Ukraine, and Kazakhstan. And we know what that’s about: an incredible, unprecedented heat wave.And here's John Podesta and Jake Caldwell in Foreign Policy last summer:
Obligatory disclaimer: no one event can be definitively assigned to climate change, just as you can’t necessarily claim that any one of the fender-benders taking place right now in central New Jersey was caused by the sheet of black ice currently coating our roads. But it sure looks like climate change is a major culprit. And it’s not just the FSU: extreme weather elsewhere, which again is the sort of thing you should expect from climate change, has played a role in bad harvest around the world.
There was already little margin for error in a world where, for the first time in history, 1 billion people are suffering from chronic hunger. But the fragility of world food markets has been underscored by the tragic events of this summer.This was something Joe Romm linked to in a scary piece today. But, for the ultimate fix of climate doom, you should subscribe to Desdemona Despair, where you'll try to swallow the output of a well-cranked firehose of news stories about floods and droughts and harvest failures all around the world.
The brutal wildfires and crippling drought in Russia are decimating wheat crops and prompting shortsighted export bans. The ongoing floods and widespread crop destruction in Pakistan are creating a massive humanitarian crisis that has left more than 1,600 dead and some 16 million homeless and hungry in a region vital to U.S. national security. These and other climate crises trigger widespread food-price volatility, disproportionately and relentlessly devastating the world's poor.
Now clearly, there are concerns about climate change affecting agriculture in the future. But look at the FAO's global data for average cereal yields, for example:
See the big slowdown? Me neither. In addition to the data (blue), I've added a linear trend, which explains 99.132% of the variance in the data, and a quadratic trend, which explains a completely insignificant additional 0.16% of the trend.
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.
But wait! you say. Aren't the wiggles in that graph getting bigger? Isn't wild and crazy weather all round the planet at least making harvests less predictable?
Well, given that nice straight line being such an excellent fit to the data, we can take the residuals (the difference between the yield each year and what the straight line said should happen), and then ask, how big is the residual as a percentage of the expected value? That basically is how big the wiggles are as a fraction of the currently expected average yield.
That's this graph:
So you can see that, as a fraction of the whole, the fluctuations in yields are actually going down over time. Slowly, ok, but still: the worlds harvest's are not only getting bigger, they are getting gradually more predictable, not less. Wild and crazy weather happened in the past too, and apparently the global agricultural system was more vulnerable to it back then.
So if food prices are at record levels, we have to look elsewhere for the cause: climate change driven yield losses or fluctuations is a non-starter as an explanation.
Update: Graph of the fraction of US corn planted which is then actually harvested. See comment discussion with kjmclark below.