Deep Freeze and Sea Breeze: Changing Land and Weather in Florida
 

The first interesting thing about talking with Roger Pielke on the subject of land cover and climate change is that he simultaneously gives the impression that everything he is saying, he has said before, and yet it is all still incredibly fascinating to him. The second interesting thing is that, even before he brings up the subject directly, you get the clear impression that not only has he made these same points before, he is also used to them being misunderstood. It’s not impatience or irritability that gives him away, but the directness of his words, the way he pauses as he talks to allow for questions, and the frequency with which he says things like “I’m not saying... What I am saying is...”

“Whenever you talk about factors other than carbon dioxide or other greenhouse gases that may be playing a role in global climate change,” Pielke says, “people immediately accuse you of trying to divert attention away from the human-influence-on-climate problem. But when I say to people that enacting the Kyoto Protocol isn’t going to solve our climate problems, I don’t mean that carbon dioxide isn’t a problem. What I mean is that, unfortunately, it may not be our worst problem.”

Three decades of research have brought Pielke to the conclusion that when it comes to the kinds of climate change people experience where they live, land surface changes like deforestation, urbanization, and the draining of wetlands are at least as important—and maybe more important—than increasing atmospheric greenhouse gases.

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  Photograph of Florida wetlands stretching to the horizon
 

In 2004, Curtis Marshall (a former student of Pielke’s), Pielke himself, and their colleagues Louis Steyaert and Debra Willard published two papers in which they demonstrate how the transformation of Florida’s wetland ecosystems in the last century may have changed the state’s climate in unexpected ways. Using present-day land cover based on Landsat satellite data, historical documents and vegetation maps, and the types of pollen found in deep soil samples, the team meticulously reconstructed how the landscape has changed in the last century. Then they used a regional climate model to compare the climate that exists with the climate that might have existed if the natural landscape had remained undisturbed.

Combining their diverse expertise in climatology, environmental modeling, ecology, geography, geology, and remote sensing, the team ended up with an explanation for how land cover change in central and southern Florida could simultaneously be responsible for hotter, drier summers and wintertime deep freezes that are longer-lasting and more severe.

 

Most of Florida’s wetlands have been drained and converted into croplands in the past 100 years. According to computer simulations, this large-scale transformation modified the regional climate in unexpected ways. In the present-day landscape, Florida days are warmer in summer, nights are colder in winter, and inland rainfall has decreased. (Photograph courtesy Deb Willard, USGS)

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