A cornfield in Indiana
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Extreme weather has visited Kevin Mainord’s farm business twice in the past two years. In 2011 a wall of water deluged his corn and soyabean fields after US authorities blasted a levee to relieve flooding on the Mississippi river. This year brought drought and weeks of devastating heat.

Scientists have long warned of more frequent floods and droughts as the world’s climate changes. But for Mr Mainord and many like him, global warming is bogus. “It’s more God and nature’s dictates, rather than a man-made event,” the Missouri farmer said this week as he harvested a corn crop one-quarter of its normal size.

Climate scepticism among farmers helps explain why carbon emissions are off the US legislative agenda despite the hottest temperatures on record.

Drought has gripped the broadest area of the US corn belt since previous severe dry spells in the 1980s and the 1930s, the National Oceanic and Atmospheric Administration said on Wednesday.

Even with plenty to lose, farmers’ champions in Washington have fought or diverted attention from climate policy to battle regulation and focus on subsidies.

Their stance defies evidence that the country’s heartland is already changing because of global warming. Farmers are adapting to these changes, whatever their professed views.

In corn belt states such as Iowa and Illinois, average temperatures had for decades been creeping higher in winter and spring amid year-to-year variations, said Deke Arndt of the climate monitoring branch at NOAA’s climatic data centre.

Higher temperatures enables skies to hold more water vapour. When the rain falls it is now more likely to arrive in powerful storms rather than in steady showers.

“The Midwest has really seen a remarkable change over recent decades in the dosing of precipitation. The overall trend is up, but the character is that more and more of that precipitation is delivered in large doses,” Mr Arndt said.

These changes have had mixed consequences for the US Midwest. Higher night-time temperatures force plants to waste energy on respiration. This reduced corn yields last summer and set the stage for the record grain rally of 2012.

“The first time that we saw a big issue with the lack of cooling at night was 1995. That’s just a function of the warming climate that we’ve seen in the last several decades,“ said Brad Rippey, US Department of Agriculture meteorologist.

Increased rainfall had spurred farmers to buy bigger equipment to plant in shortening time windows between storms and install field drainage systems, said Jerry Hatfield, director of the USDA’s national laboratory for agriculture and the environment in Iowa.

Wetter weather along with cheaper land and new water-capturing tillage practices had also catapulted South Dakota, in the northern plains, into a big producer of soyabeans, Mr Hatfield said. The state was on track to harvest 4.5m acres of the oilseed this year, up 456 per cent from 30 years ago.

“Some of the things people were talking about in climate change are really starting to come through in the climate signal,” Mr Hatfield said.

“Warmer conditions, more variable rainfall, more extreme events – things we have talked about are actually appearing. We do have some change under way, and the magnitudes of these changes are important to realise.”

Other changes to be expected in a warmer environment, such as new pest species, were difficult to cite as a fingerprint of climate change because many other factors also determined their survival, said Karen Garrett, plant pathology professor at Kansas State University.

The 2012 drought does not fit with the trend towards wetter weather. Many scientists are reluctant to say whether fleeting events reflect bigger trends.

Recent academic studies by James Hansen of Nasa and officials from NOAA and the UK’s Met Office have linked summer heatwaves and climate change, however. “Today’s extreme anomalies occur as a result of simultaneous contributions of specific weather patterns and global warming,” Mr Hansen wrote.

By 2030, climate change would cost corn belt farmers between $1.1bn and $4.1bn annually while pests reduce the region’s crop acreage, USDA economists forecasted last month.

Many farmers seem unworried. In an Iowa State University poll, 5 per cent of Iowa farmers believed the climate was changing and 28 per cent believed there was insufficient evidence to know if it was or not. Sixty-eight per cent acknowledged climate change but only 10 per cent attributed it to humans.

Forty-six per cent of those polled said crop insurance and similar programmes would protect farms regardless of whether climate change was happening. Government-backed crop insurance cost US taxpayers more than $8bn last year.

These views translate into public policy. Opposition from the 6.2m-member American Farm Bureau Federation helped defeat Congress’s last attempt at climate legislation.

Farmers were “not overly” concerned about global warming, said Don Lipton, federation spokesman. “They’re of the view, and this is a broad generalisation, that the science is not necessarily determinant”.

Tom Vilsack, US agriculture secretary, has announced the government will spend $170m to buy meat to help drought-hit livestock farmers and is pushing for farm bill to assist growers and ranchers.

Asked about prospects for capping greenhouse gas emissions, he said: “The focus for us is on research”. This, he said, would help agriculture adapt to “whatever climate circumstances we confront, whether it’s more extreme heat, whether it’s excess water, whether it’s more extreme storms”.

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