By Jeff Gillies
JeffGillies@gmail.com
Great Lakes Echo
Aug. 18, 2009
Four Great Lakes states recorded their coolest July this summer in 115 years of record keeping. Two more recorded their second coolest July.
What ever happened to global warming?
“Nothing,” said Jeff Andresen, Michigan’s state climatologist.
“The long term patterns are still pretty much in the same direction as they’ve been,” he said. “And that’s a warmer region and world.”
While Great Lakes cities and states set records for cool July temperatures, New Mexico had its third warmest July. Arizona and Washington each had their ninth warmest July.
Globally, the combined land and ocean surface temperature for July 2009 was the fifth warmest on record, according to the preliminary data from the National Oceanic and Atmospheric Administration’s National Climatic Data Center. It was also the 33rd straight July with an average global temperature above the 20th century normal.
“At the same time that we were cooler than usual, there were other areas that were the exact opposite,” Andresen said. “Much hotter than normal.”
But there’s still no doubt that this has been a cool summer in the Midwest.
This was the coolest July on record in Ohio, Illinois, Indiana and Pennsylvania. It was the second coolest in Michigan and Wisconsin and the third coolest in Minnesota.
Michigan hasn’t seen a July this cool since Mount Pinatubo’s massive eruption over the Philippines in 1991, Andresen said. That explosion sent so much dust into the atmosphere that enough sunlight was blocked out to drive down global temperatures.
“But this year we don’t have any volcanoes,” Andresen said.
Instead, we have the jet stream, a narrow band of fast moving air that circles the globe and blows from west to east. Throughout June and July, the jet stream snaked north into Canada and picked up masses of cold air, Andresen said. Then it turned south and brought that cold air to the Midwest.
It’s not unusual for the jet stream to bring cool Canadian air to the region. But it usually doesn’t persist for as long as it did this summer, Andresen said.
And a stubborn jet stream doesn’t just mean fewer days at the beach. Corn and soybean crops aren’t maturing as quickly as they have the last five years, said Gerald Tillman, deputy director of the Michigan Agriculture Statistics Field Office.
A few cool summer months don’t mean that there’s no hope for this year’s harvest.
“Sometimes mother nature catches up with the crop,” Tillman said. “If we’ve got a warm August and a warm September, and the fields have enough moisture, than it’ll catch up.”
Andresen said it’s reasonable to expect cool spells to drive some confusion about global warming. But changes that occur over the span of a few weeks don’t mean that long-term patterns have changed.
“These relatively short term variations in weather don’t make shifts in climate,” he said. “It has to take place on long, extended periods of time.”
David Thornton hasn’t noticed any uptick in climate change skepticism in Minnesota driven by the cool summer.
But that doesn’t mean that the region’s cooler short term trend is not playing into national politics regarding the long term issue of global warming, said Thornton, an assistant commissioner of that state’s Pollution Control Agency and part of a climate change advisory group.
He has seen national media reports connecting the cool summer to the ongoing debate in Washington D.C. over a bill that would regulate greenhouse gas emissions.
“I do think folks are pointing to the cooler summer as a reason to be skeptical of the need for climate change legislation,” Thorton said.