One reason many Midwestern producers don't buy anthropogenic global warming (AGW) is what they experience when they walk out the door. The availability bias makes the last few summers (cool and wet) weigh more heavily in their estimates of what is really going on.
One guy thinks it's possible we have made our own microclimate all by ourselves.
In place of those dry, 90-degree scorchers are the kind of lingering 80-degree days with higher humidity that don't cool down much at night. Climate scientists say the cause is rising dew-point levels — the measure of water vapor in the atmosphere.Coupled with predictions of altered storm paths, this adds to the growing uneasiness that cool and wet maybe the norm for a while. The time frames involved are too short to verify any of this, but waiting until we do find out offers little chance for big rewards.
These high dew-point levels are important, said David Changnon, a climate scientist at Northern Illinois University who helped pioneer this research, because even though the temperature is lower, the heat index is higher. And that's bad news for many city dwellers, since those conditions contributed to the deadly heat waves that hit Chicago in 1995 and 1999.
Already, these cooler but muggy late-summer days are likely to be producing more powerful thunderstorms and periods of heavier rain that bear watching, Changnon said.
"While we're seeing fewer really hot days, we've created dew points in Chicago and around the Midwest that are unheard of," Changnon said. "And it begs the question, 'How the heck can we do that?'"
Changnon's theory, backed by more than a decade of research, is that more densely planted corn and soybean fields scattered across the Midwest are changing the regional climate by releasing more water vapor into the atmosphere. The more water vapor that reaches the atmosphere, the higher the dew point, and the fewer extremely hot summer days.
In other words, while some still question whether people are to blame for changing weather patterns around the globe, farmers around the Midwest are already altering the region's climate in significant ways, Changnon said. [More]