Some scientists are now saying that due to climate change, high temperatures could be adversely affecting agricultural crops as much as rain irregularities. In the US, high temperatures have now diminished the yield of many crops and vegetables. The problem appears to be both a rise in day-time temperatures combined with high night-time temperatures. The magnitude of recent temperature trends is larger than those of precipitation in most cases.
High night-time temperatures have a negative impact on yield, as heat affects evaporation and the life process of the crop, which becomes compressed. And when the atmosphere gets warmer, the atmospheric demand for water increases.
In the deep south of the US, tomatoes can no longer be grown in summer because of pollination problems. The same applies to snap beans.
Ken Boote at the University of Florida found that rice and sorghum plants failed to produce grain when the average 24-hour temperature is 35 ░C. Drought is often blamed for poor crops, and indeed drought-resistant crops are currently being researched, but the situation is complex because higher temperatures in turn mean that more water is required.
A climate study of world corn, wheat, soybean and rice yields over the last three decades (1980-2008) was published in May 2011 and conclued that it was heat, not rainfall, that affected plant growth the most. The impact of heat on plant growth needs more study, scientists say.