Climate Change: How Extreme Heat May Affect Your Food

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Hot enough for you? If you live in one of the more than 15 states that were suffering under a heat advisory or excessive heat warning on Tuesday, I’m going to guess the answer is yes, God, please make it all stop. The oppressively high temperatures that gripped much of the U.S. during June—the hottest month on record worldwide, according to the National Oceanic and Atmospheric Administration (NOAA)—barely relented in July, when average temperatures around the country were 1.3 F higher than the 20th century norm. In New York where I live, this past July just missed being the hottest month on record in the city, but air conditioners still ran overtime—the city had the highest electricity use ever last month. Of course it could be worse—in Moscow unusual and unrelenting heat and smoke from wildfires has killed as many as 700 people a day, and meteorologist Jeff Masters of Weather Underground estimates that the death toll could be as high as 15,000 by the time the temperatures drops:

The only comparable heat wave in European history occurred in 2003, and killed an estimated 40,000 – 50,000 people, mostly in France and Italy. While the temperatures in that heat wave were not as extreme as the Russian heat wave, the nighttime low temperatures in the 2003 heat wave were considerably higher. This tends to add to heat stress and causes a higher death toll. I expect that by the time the Great Russian Heat Wave of 2010 is over, it may rival the 2003 European heat wave as the deadliest heat wave in world history.

Here’s where I insert the usual caveat that no current weather event can be said to be “caused” by climate change—and that goes for killer heat waves too. (And when we add up the number of people killed by extreme heat, it’s important to remember that cold is a killer too—in fact, hundreds have died from an unusually cold winter this year in South America.) But as my Ecocentric colleague Michael Lemonick wrote recently, one thing we can expect from continued climate change is increasingly extreme heat. That message is reinforced by a report out today from the National Wildlife Federation (NWF), which shows both how unusual the current heat hitting much of the U.S. is, and maps out how much hotter its likely to get in future summers. (Just one example: my hometown of Philadelphia is projected to have 60 days of temperatures exceeding 90 F by midcentury under high greenhouse gas emissions projections—during this year’s brutal summer, the city is projected to have around 30 such days.) Here’s NWF climate scientist Amanda Staudt explaining the report:


As anyone who has ever tried to navigate New York’s infernal subways during a humid August scorcher knows, more heat waves will suck. But the greater impact of greater heat could be on our ability to feed ourselves. Already the extreme drought and heat has badly damaged grain harvests in Russia, Kazakhstan and Ukraine, the old Soviet breadbasket responsible for one-fourth of the world’s wheat exports. Russia’s grain harvest could drop from 94 million tons to 65 million tons or less this year—an alarming figure that prompted Moscow to ban grain exports, steps that could be followed by its neighbors. As my TIME colleague Michael Schumann writes today at Curious Capitalist, wheat prices worldwide have surged 50% since early June, the biggest leap in 30 years, and there are long-term fears as well:

Today’s wheat scare is the just latest sign of what could be one of the biggest challenges facing the global economy over the next 20 years – the fight to feed the world. We’re suffering from three decades of neglect of agriculture, a period when the sector was starved of the resources and technology it needs to keep up with rising world demand. And though there is a growing global consensus about the need for a second Green Revolution, we’re really only at the beginning of a long, expensive process of repairing the world’s farms. That means we’re likely to see higher food prices overall over the next decade, and the continued risk of dangerous price fluctuations like the one we’re experiencing now with wheat.

Climate change won’t make that any easier. As the agronomist Lester Brown writes at Treehugger, higher temperatures tend to shrink harvests:

The rule of thumb used by crop ecologists is that for each 1 degree Celsius rise in temperature above the optimum we can expect a reduction in grain yields of 10 percent. With global temperature projected to rise by up to 6 degrees Celsius (11 degrees Fahrenheit) during this century, this effect on yields is an obvious matter of concern.

Each year the world demand for grain climbs. Each year the world’s farmers must feed 80 million more people. In addition, some 3 billion people are trying to move up the food chain and consume more grain-intensive livestock products. And this year some 120 million tons of the 415-million-ton U.S. grain harvest will go to ethanol distilleries to produce fuel for cars.

Grain isn’t the only crop that will under more intense heat. The production of rice—the world’s most widely consumed grain, with some 700 million metric tons produced a year—could suffer as temperatures rise, according to a study published Monday in the Proceedings of the National Academy of Sciences. The study—led by Jerrod Welch, a graduate student of economics at the University of California-San Diego—analyzed data from more than 200 rice farms in six Asian countries. They found that higher daytime temperatures actually increased rice yield—up to a point—but that hotter nights tended to cut yields:

“Up to a point, higher day-time temperatures can increase rice yield, but future yield losses caused by higher night-time temperatures will likely outweigh any such gains because temperatures are rising faster at night,” said Welch. “And if day-time temperatures get too high, they too start to restrict rice yields, causing an additional loss in production.”

That doesn’t mean farmers will be helpless to adapt to rising temperatures. Agricultural research groups are already hard at work developing new strains of rice or wheat that can better withstand dry and hot weather—although cutbacks have long threatened farming research. If we can’t beat the heat, we may find we don’t have anything to eat. (Sorry for the rhyming—I blame the heat.)