Weather Forecast



Climate change will affect U.S. agriculture in destructive ways, according to a U.S. Department of Agriculture report. (Erin Brown/Grand Vale Creative)

 Despite 'a mountain of evidence' for climate change, doubt remains

Editor's note: Jonathan Knutson received a fellowship from the North American Ag Journalists to attend the Society of Environmental Journalists' recent annual convention in Pittsburgh. He is not a member of the group.

PITTSBURGH — Andrew Dessler compares current public debate over climate change to the long-concluded debate over smoking.

"People pretty much knew that smoking was bad in the 1950s, and there was evidence even as early as the '30s." The influential 1964 Surgeon General report on Smoking and Health effectively ended honest debate on the subject, said Dessler, a professor of atmospheric sciences at Texas A&M University.

Even so, it took until the 1990s for tobacco industry executives to acknowledge that smoking is harmful, said Dessler, who spoke at the recent annual convention of the Society of Environmental Journalists in Pittsburgh.

Now, "There's a mountain of evidence" that climate change exists and that human activity is the primary cause — though skeptics continue to assert otherwise, just as some people once insisted that smoking doesn't cause cancer, Dessler said.

Most of the skepticism about climate change involves the claim that human beings are responsible. Many in ag argue that the climate is always changing and that little, if any, of the current change is man-made.

Dessler agreed that "attribution" — whether nature or human activity is responsible — is at the core of the controversy. Four separate arguments — including theoretical, climate models and the lack of a competing hypothesis — all support the conclusion that carbon dioxide generated by human activity is the overwhelming cause of current warming.

But what about climate change that occurred long before human-generated carbon dioxide?

Dessler said those changes clearly were caused by carbon dioxide generated by nature. Now, climate changes are caused by carbon dioxide from human activity.

"Carbon dioxide is still the cause. But now, human activity, not nature, is generating it," he said.

This much is agreed on by everybody: climate change is one of the most influential issues in modern agriculture. Some in ag — including the U.S. Department of Agriculture — say climate change will have a huge impact and require farmers and ranchers to operate differently.

A 2013 USDA report found, among other things, that climate change will do the following:

• "Reduce productivity of crops."

• Put livestock production systems at greater risk.

• "Have overall detrimental effects on most crops and livestock" by 2050 and beyond.

The National Farmers Union, one of the nation's two largest general farm membership organizations, also is concerned about climate change. Farmers and ranchers "face severe challenges" from it, Tom Driscoll, director of NFU Foundation and Conservation Policy said in a telephone interview.

Climate change has been determined to be "a special order of business, membership's most urgent way of calling for action," he said.

"There's a sense we need to be finding policy solutions to encourage farmers to take action to adapt to and mitigate climate change, as well as efforts in education," Driscoll said.

The American Farm Bureau Federation, the nation's other major farm membership organization, takes a different slant.

The organization has "diverse" membership and doesn't have an official position on climate change, Andrew Walmsley, the organization's director of Congressional Relations, said in a telephone interview.

"Farmers aren't out there on a daily basis debating climate change" or "what the science does or doesn't say," Walmsley said. Rather, the Farm Bureau and its members support innovation and entrepreneurship that help farmers and ranchers, not regulations that hurt them,

"American farmers adapt to whatever challenges are thrown at them. Don't stifle us, give us access to the tools we need," he said.

'Climate-change deniers'

As Dessler noted, Americans' view on the dangers of smoking changed over time.

A 1958 Gallup survey found that 44 percent of Americans believed smoking causes cancer. By 1968, another Gallup survey found, the number had climbed to 78 percent.

Now, Gallup surveys find public acceptance of climate change is rising, too. The number of Americans that the organization terms "concerned believers" on climate change has risen from 37 percent in 2015 to 47 percent in 2016 and to 50 percent in the spring of 2017.

Even so, there's a "coalition of climate-change deniers" who use varying arguments against the scientific validity of climate change, Rebecca Leber, an environmental reporter with Mother Jones magazine, and David Masur, executive director of PennEnvironment, a nonprofit environmental group, said at the Pittsburgh conference.

Trying to change the minds of ardent critics/deniers of climate change is probably useless, but people without strong views can be persuaded, Leber, Masur and Dessler said.

That seems to be happening. Gallup finds that the number of Americans in what it calls the "Mixed Middle" on climate change fell from 45 percent in 2012 to 31 percent in the spring of 2017.

Pro and con arguments

Dessler said anti climate-change arguments fall into three general categories:

• Process arguments, which contend the process/procedure of science is flawed. "It's trying to discredit science."

• Science arguments, which are "relatively rare." People who use these "don't flatly contradict science, they just say we really don't know."

• Delay arguments. "They say, 'I believe in the science. But it's not something we should worry about.' (But), people who use this really don't believe in the science."

The pro climate-change argument can be summarized like this, according to Dessler:

Earth's temperature is warming; both surface and satellite measurements confirm it. What's more, things that depend on temperature — such as melting ice — further confirm it.

"There's this interlocking web of data that shows Earth is definitely warming," and that carbon dioxide generated by human is the primary cause, Dessler said.

"Imagine you were on a jury and the prosecution came up and said, 'We have all this evidence that carbon dioxide did it. And there's no other suspects.' You'd be hard-pressed not to find carbon dioxide guilty beyond a reasonable doubt. It's not behind a shadow of doubt, because there's always doubt, But it's not reasonable doubt," Dessler said.

Costs, winners and losers

Concern about the cost of responding to climate change is legitimate. But the cost of dealing with past environmental issues such as acid rain ended up far lower than many people predicted, Dessler said.

"If you tell the free market, substance x will be regulated — the free market is incredibly clever and they will come up with alternatives to substance x," he said.

Another argument in the climate change debate is that some regions will win, while others will lose. The Upper Midwest is sometimes projected as a winner because its growing season is lengthening.

Driscoll, with the National Farmers Union, said that assumption is dangerously flawed.

Based on what he's read, climate change over time "will bring rapidly escalating weed, insect and (crop) disease pressure," as well as more intermittent and destructive precipitation, in addition to longer growing seasons.

"How much do you really want a longer growing season if you're spraying all the time" to combat weeds, insects and crop disease, he asked.

"Farmers deal with enough uncertainty already. They don't need more," Driscoll said.

Dessler said ag producers, like other Americans, live in a connected world. If climate change damages China's economy, for example, lost U.S. ag exports to China would far exceed any benefit from a longer growing season.

"The idea that some people will be net winners is real dubious to me. I find it hard to believe that anyone will be better off," he said.

Washington developments

By all accounts, the Trump administration is skeptical of climate change and is working to slow the federal government's response to it. Walmsley, with the American Farm Bureau Federation. said he doesn't see "the political will" in Washington, D.C., to push for stronger action anytime soon.

Driscoll, with the National Farmers Union, said, "We cannot look to the federal government to be leaders in this."

That's encouraging the private and philanthropic sectors to be "extra-motivated" on climate change, he said. "We see a lot more creativity and hard work at the state level, as well."

Driscoll's advice for agriculturalists who are uncertain about climate climate: "Consult a wide spectrum of sources to get this information."

Dessler said the vast majority of Americans will, over time, recognize the danger of climate change. By his reckoning, based on what happened with smoking, that will happen sometime in the 2020s.

"Ultimately, everyone will accept climate change," Dessler said.

'Scientific consensus'

There's widespread disagreement in agriculture and elsewhere whether climate change exists and whether human activity is responsible. Many in agriculture argue that climate change is caused primarily or entirely by nature; they insist there's no evidence that human beings are responsible.

But NASA, the National Aeronautics and Space Administration, offers this assessment:

"Multiple studies published in peer-reviewed scientific journals show that 97 percent or more of actively publishing climate scientists agree: Climate-warming trends over the past century are extremely likely due to human activities. In addition, most of the leading scientific organizations worldwide have issued public statements endorsing this position."

More information on what NASA terms "Scientific consensus: Earth's climate is warming:"


To learn more

Climate change is controversial, to say the least, in modern agriculture. It's important to draw on a range of information before making up your mind. These sources can help:

• The U.S. Department of Agriculture 2013 report on on how U.S. ag is affected by climate change:

• A 2016 National Farmers Union fact sheet on climate change:

• The American Farm Bureau Federation policy statement on climate change:

• The web site of the Intergovernmental Panel on Climate Change, the international body for assessing the science related to climate change: