When it comes to variations in crop yield, climate has a big say

What impact will future climate change have on food supply? That depends in part on the extent to which variations in crop yield are attributable to variations in climate. A new report from researchers at the University of Minnesota Institute on the Environment has found that climate variability historically accounts for one-third of yield variability for maize, rice, wheat and soybeans worldwide -- the equivalent of 36 million metric tons of food each year. This provides valuable information planners and policy makers can use to target efforts to stabilize farmer income and food supply and so boost food security in a warming world.

The work was published in the journal Nature Communications by Deepak Ray, James Gerber, Graham MacDonald and Paul West of IonE's Global Landscapes Initiative.The researchers looked at newly available production statistics for maize, rice, wheat and soybean from 13,500 political units around the world between 1979 and 2008, along with precipitation and temperature data. The team used these data to calculate year-to-year fluctuations and estimate how much of the yield variability could be attributed to climate variability.About 32 to 39 percent of year-to-year variability for the four crops could be explained by climate variability. This is substantial -- the equivalent of 22 million metric tons of maize, 3 million metric tons of rice, 9 million metric tons of wheat, and 2 million metric tons of soybeans per year.The links between climate and yield variability differed among regions. Climate variability explained much of yield variability in some of the most productive regions, but far less in low-yielding regions. "This means that really productive areas contribute to food security by having a bumper crop when the weather is favorable but can be hit really hard when the weather is bad and contribute disproportionately to global food insecurity," says Ray. "At the other end of the spectrum, low-yielding regions seem to be more resilient to bad-weather years but don't see big gains when the weather is ideal." Some regions, such as in parts of Asia and Africa, showed little correlation between climate variability and yield variability.More than 60 percent of the yield variability can be explained by climate variability in regions that are important producers of major crops, including the Midwestern U.S., the North China Plains, western Europe and Japan.Depicted as global maps, the results show where and how much climate variability explains yield variability.

The research team is now looking at historical records to see whether the variability attributable to climate has changed over time -- and if so, what aspects of climate are most pertinent.

"Yield variability can be a big problem from both economic and food supply standpoints," Ray said. "The results of this study and our follow-up work can be used to improve food system stability around the world by identifying hot spots of food insecurity today as well as those likely to be exacerbated by climate change in the future."

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Active 2011 Hurricane Season Comes to an End (LiveScience.com)

The 2011 Atlantic hurricane season was forecast to be a doozy and it delivered.

The season officially ends tomorrow (Nov. 30) and its legacy includes 19 tropical storms, seven hurricanes and three major hurricanes — including the devastating Hurricane Irene, the only hurricane to strike the United States this year. Irene was the first U.S.-land-falling hurricane in three years. Its billion-dollar damage brought the United States back to the reality of hurricanes after years of quiet.

"Irene reminded us that the Northeast can and does get hit byhurricanes," said Jeff Weber, an atmospheric scientist at the University Corporation for Atmospheric Research in Boulder, Colo.

Active trend

The 2011 season continued a trend of active hurricane seasons that began in 1995, according to the U.S. National Oceanic and Atmospheric Administration (NOAA). Tropical storms came in with the third-highest total, at 19 (tied with 1887, 1995 and 2010), since records began, in 1851. An average season has 11 tropical storms. [See a video of the season's storms.]

The seven hurricanes and three major hurricanes (Category 3 or higher on the Saffir-Simpson Hurricane Scale) that developed this year number only slightly above the averages of six and two, respectively.

The 2011 season affected the Mid-Atlantic more than the Gulf of Mexico. Hurricane Irene, the first hurricane to hit the United States since Ike hit Texas in 2008, socked the East Coast. The storm caused $7 billion in damage and became the worst tropical cyclone  to strike the Northeast since Hurricane Bob in 1991. Tropical cyclone is the generic term for tropical storms and hurricanes.

Irene inundated New York and Connecticut with water — up to 15 inches (38 centimeters) in some places. Irene was blamed for 46 deaths across 13 states.

As bad as the damage was, things could have been worse. Modern storm-tracking technology allowed NOAA forecasters to accurately map Irene's path for four days before its landfall Aug. 27, near Cape Lookout, N.C., allowing the population of the Outer Banks to evacuate. Irene was a major storm for a brief period, but it weakened to a Category 1 storm and so was not a major hurricane at landfall.

"We have now gone six years — since Wilma in 2005 — without a major hurricane making U.S. landfall," said Phil Klotzbach, an atmospheric scientist and hurricane forecaster at Colorado State University.

Few Gulf storms

Since 1878, when land-falling hurricane records begin, the 2006-2011 span is the longest stretch without a major hurricane hitting the United States, Klotzbach told OurAmazingPlanet.

While the East Coast was soaked by storms, the dearth of Gulf storms added tothe Texas drought.

One storm that did hit the Gulf was Tropical Storm Lee, which made landfall in central Louisiana. Lee spawned 38 tornadoes, the second most on record for a tropical storm.

Most storms were turned away from the United States by an anomalous trough of low pressure along the East Coast, "which helped steer storms moving towards the U.S. coast back out to sea before they could make U.S. landfall," Klotzbach said.

You can follow OurAmazingPlanet staff writer Brett Israel on Twitter: @btisrael. Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet and on Facebook.

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