Climate change is already here...for farmers at least

A couple of recent studies indicate that climate change is already reducing crop yields around the world, and has reduced the global food harvest by about 40 million tons a year over the last 20 years. This is a small fraction of the 2 billion tons harvested in total. But it still represents a few billion dollars and is even more costly to the farmers who are hardest hit by drought, flooding, or extreme heat and cold.

One study, published in Environmental Research Letters, revealed a simple relationship between temperature and crop yields, with a drop in yields of between 3 and 5 percent for every 0.5 degree Celsius increase in average temperature. Earlier experiments exposing greenhouse plants to higher temperatures (and carbon levels) have shown a similar decrease.

In a 2005 Worldwatch article, I described how climate change would likely affect farmers around the world and what they are doing to adjust. More recently, a New York Times story profiled farmers from four regions who have been forced to adapt to the rapidly changing weather.