The topic of global warming is polarizing. But just for a minute, put aside any doubts, and consider the doomsday prophets correct. Assume that temperatures are heating up, fossil fuels are chiefly to blame and that, if not corrected quickly, terrible consequences will follow.

More importantly, consider global warming's impact on farming. How, with highly unpredictable weather, will farmers grow crops? How will insects and diseases react?

The Center for Health and Global Environment (CHGE) at Harvard's Medical School is on the case and being listened to. Lately, our country's policymakers — despite party affiliation — are paying close attention to the expert scientists assembled by the center for briefings and instruction. For the last five years (with more planned), the center has held classes attended by congressional staffers.

On Sept 29, four senators from Midwest farming states co-sponsored a Senate Agricultural Committee briefing. Scientists who spoke to the senators had been brought in by the CHGE.

Following that briefing, Delta Farm Press spoke with Eric Chivian, CHGE director. Besides piloting the CHGE, Chivian is a medical physician and also grows fruit trees in New England. Among his comments:

DFP: Farmers are used to wild swings in the weather. Farmers seeing drought occurring in one part of farmland while excessive moisture is experienced in another isn't anything new. It would seem that part of the argument for global warming is just par for the course for many producers. No rain this year? Next year, the rains will come. I'm wondering if you can approach this as a farmer and lay out the case for global warming from that perspective…

Chivian: “It's tricky because you're dealing with something that changes all the time anyway. And it changes in different places at different times. Half of Arkansas can be very wet one year and very dry the next.

“(Understanding this) involves an ability to look at trends and see whether those trends mean the climate is changing. There are many farmers who are doing just that… particularly in parts of the corn and soybean belts. Farmers there are seeing the last several years as being quite different in terms of temperatures and drought conditions.

“This is especially true in places like Kansas, Nebraska and Iowa. They're also noticing differences in crop diseases and pests that they've never seen before.

“I think there are many farmers that appreciate that conditions are changing over time. True, conditions change yearly. But if you look back you can see that agriculture is becoming much more variable in the United States.

“(At the Senate briefing, Bill Easterling, Penn State University professor and head of the agriculture section of the Intergovernmental Panel on Climate Change) showed a graph on how, over the last 20 or 30 years, agricultural productivity in the United States has been on the increase. However, there have been marked dips in productivity related to weather, crop diseases and pests that show the trend is becoming more variable.

“That, in many ways, is the more important story for farmers. Yes, there's temperatures and warming and we're seeing more extreme weather events… but, by and large, the situation is becoming more unpredictable and unstable.

That's a very difficult situation for farmers who must make decisions on types of crops, when to plant, what (chemicals) to use. If those kinds of predictions can't be made, you're in big trouble.

“A warming world caused by greenhouse gases will lead to more variable and unstable weather. It will make things very difficult for farmers.”

DFP: How do you find your message is being received now versus a decade ago?

Chivian: “One thing that was interesting about this briefing is it was co-sponsored by Senators Lugar, Harkin, Brownback and Nelson. All of them are from major farm states — Iowa, Kansas, Indiana and Nebraska.

“Senators Brownback and Nelson, in particular, haven't been in the frontlines among those concerned about climate change. They've been thoughtful, but fairly conservative members of the Senate. It's noteworthy that they are now increasingly concerned about the issue of climate because farmers in their states have been very badly hit in recent years.

“Sure, if you look back in time, you can say, ‘well, we had severe droughts in the 1930s and we had very heavy rains in 1978.’

“Historically, you can look back and say that what's happening now isn't the worst ever — although, in some cases, there have been record temperatures and droughts in recent years.

“But the trend shows that there are increasing numbers of extreme weather events. For example, in Kansas this summer… parts of the state received temperatures over 100 degrees — in some cases 110 degrees — for several days in a row.

“That meant the soil was completely dried out. This August, millions of soybean and corn acres in Kansas, Nebraska and parts of Iowa were wiped out by temperatures and lack of rain.

“Then, beginning in September, there were very heavy rains. If you average out the rainfall over a few months, it appears the rain was normal. But that's no good for the farmers because the rains came too late for the crops.

“And the rains were too heavy besides, causing run-off and erosion. These rains weren't terribly useful for the farmers.

“We humans aren't programmed to look long-term — myself included. If it's a really hot summer, I don't remember how cold the winter was. I'm just concerned about what's going on now. So, it doesn't surprise me that some aren't seeing the trends as clearly as the record books show.”

DFP: On farmers being an environmental trip-wire:

Chivian: “We hope that farmers are more able to see these trends because, much of the time, they often plan what to do this growing season based on what happened last.

“The other part of this story that's important isn't just the temperatures and the amount of rainfall. The climate changes also affect biological systems — pests and diseases.

“Iowa State's X.B. Yang (who, at the briefing, spoke on climate change and effects on crop diseases and pests) has some fascinating and extremely important data. What he reports is that some of these crop diseases and pests, when the weather warms, overwinter in more northern regions where the pests haven't been before.

“Sudden Death Syndrome (SDS), the second biggest destroyer of soybean crops in Iowa, was, in the 1970s, confined to a small area of Arkansas. By the end of the 1990s, it had moved northward and east and was then at the northern border of Iowa. It's since moved into mid-Minnesota.

“So SDS, a fungal disease, hadn't been very far north. But as temperatures warmed, it's been able to move into more northern areas.

“There's another part of the story that's very important: as weather is changed, you also change the range and reproductive rates of insects. Insects may normally only have one reproductive cycle per year. But if weather gets warmer and the season is extended, they may have two reproductive cycles and therefore be much more devastating to crops.”

DFP: Who does your group advise?

Chivian: “We're physicians, public health experts and environmental scientists. The first purpose of the group is to understand the impacts to human health from the effects we're having on the environment — not so much locally, but more global. We're interested in global warming, ozone depletion, oceans, loss of biodiversity. We want to understand those effects and then serve an education role and be a resource for a variety of groups, including the medical and scientific communities.

“Another big part of our work is to be a resource for policymakers. That includes the U.S. Congress. We've taught a course for congressional staffers for the past five years and held 11 congressional briefings where we bring in the people we believe are the most expert in the areas we're trying to cover. We present the best and most current scientific understandings of these issues.

“We're not an advocacy group and aren't trying to lobby for any legislation one way or the other. We want to be an information source. Hopefully, by informing policymakers, they can make the best decisions about these issues.”

DFP: How do you speak to naysayers? Are you finding them to be fewer now? Are they becoming more vociferous in their views?

Chivian: “That's a really good question. I think in our experience, there are two groups of naysayers. There are skeptics who have really valid and scientific questions about data and conclusions drawn by the international scientific community.

“There are a few researchers who publish and are peer-reviewed by colleagues.

“Then, there is a group of people who, in my view, are more ideologically or politically motivated. Or, they're working for industry that isn't crazy about the notion that fossil fuels are maybe causing these changes in the Earth's climate and composition in the atmosphere. Those people are much less credible, and their conclusions are much more suspect.

“Having worked on these issues for 15 years or so, I don't believe there's any serious debate in the international scientific community that (1) the fact that the composition of the atmosphere has changed with more carbon dioxide, and (2) there's been warming on the Earth's surface over the last century. There's also little debate, and no significant disagreement, that human activity has been largely responsible for that warming.

“As you say, there are naysayers. But they've gotten fewer in number and much less influential. It's pretty mainstream science that global warming is occurring, and we're largely the cause of it. We'd better start doing something about it now.”

DFP: On that note, how long do we have?

Chivian: “I think the climate is already changing. The concern that many of us have is that the levels of carbon dioxide that we're releasing into the atmosphere now will be sticking around for 100 years. Carbon dioxide has an atmospheric life of 100 years or more.

“So we're making changes that will outlast our great-grandchildren. That's a responsibility downstream in future time that we should be much more aware of. We have no right to negatively affect the lives of people 100 years from now. We need to start taking this issue seriously now. And many people are — the good news is that this briefing we just held had strong bi-partisan support.”

Editor's note: For more information on CHGE and the recent Senate briefing, see www.med.harvard.edu/chge.

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