Climate change is leading to such extreme variability in precipitation, increased and more severe heat waves, and severe weather events that world governments need to prepare for natural disasters—including crop failures that lead to food insecurity.
In a major report released last month, the United Nations’ Intergovernmental Panel on Climate Change said: "Evidence suggests that climate change has led to changes in climate extremes such as heat waves, record high temperatures and, in many regions, heavy precipitation in the past half century."
The Nobel Prize winning scientific panel made up of 220 authors from 62 countries, drew the following conclusions in Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation:
- The length or number of heat waves has increased in many regions of the world.
- The frequency of heavy precipitation events, particularly in the high latitudes and tropical regions as well as in the northern mid-latitudes, has increased.
- The duration and intensity of droughts, particularly in Europe, central North America, Central America, Mexico, northeast Brazil, and southern Africa have increased.
"It will be difficult for agriculture to cope with all of this variability," says Jerry Hatfield, director of USDA’s National Laboratory for Agriculture and the Environment, Ames, Iowa. Hatfield was a lead author on one of the report’s chapters, "Changes in Impacts of Climate Extremes: Human Systems and Ecosystems."
Hatfield says that the severity of last year’s exceptionally hot summer in the U.S. Midwest as well as the current drought in the southern plains are connected to climate change. "We have a shifting precipitation pattern," he says. In the U.S. Corn Belt, for instance, there is a tendency for more rain during the spring season and less in the summer coupled with higher temperatures.
Last year, rains delayed planting in a large swath of the Corn Belt. "In the southern plains and southern Corn Belt, precipitation will become more variable year to year and within the season," he says.
Historically, major droughts have occurred on about a 20-year cycle. "The likelihood of a major drought today could be once every 15 or 10 years," Hatfield says. Economic losses from these extreme events will also accelerate and the span of droughts could increase. "There is a tendency for droughts in the southern plains to extend farther into the Midwest," says Hatfield. "We’ll see an expansion of the dry area this year. We have come through a really warm winter and an extremely warm March. We have evaporated a lot of the moisture from the soil back into the atmosphere."
Climate change has led to more warm spells and heat waves, which in turn have put a lot of pressure on water use, says Hatfield, and that could make global crop production more variable year to year. "High temperature events can be as damaging to the crops as a lack of water," he says. Not only does the plant need to transpire more to keep cool, but extreme heat can kill the pollen.
Spain and Portugal have had their driest winter in 70 years. "They are going into the growing season with almost no water stored," says Hatfield. The situation for the countries’ cash crops—mostly vegetables, exported to other European countries—is very serious. "An extreme event is already shaping up," he adds.
As these types of extreme events increase and growing conditions become more variable, there will be tremendous impacts on the global food supply, according to Hatfield. Governments need to pay attention and prepare.