Opinion

Earth getting warmer, human activity the cause

Sailboats and a floating dock lie on the dry, cracked dirt in a harbor at Lake Hefner in Oklahoma City. This July was the hottest month in a century. Yes, the heat is on for climate-change skeptics. Sailboats and a floating dock lie on the dry, cracked dirt in a harbor at Lake Hefner in Oklahoma City. This July was the hottest month in a century. Yes, the heat is on for climate-change skeptics. Photo: Associated Press Photo: Associated Press Image 1 of / 1 Caption Close Earth getting warmer, human activity the cause 1 / 1 Back to Gallery

Listen carefully and you can almost hear nature, in a parched voice ask, “What part of ‘hottest month ever' do you people not understand?”

According to the National Oceanic and Atmospheric Administration, July was indeed the hottest month in the contiguous United States since record-keeping began more than a century ago. That distinction was previously held by July 1936, which came at the height of the Dust Bowl calamity that devastated the American heartland. The average temperature last month was 77.6 degrees — a full 3.3 degrees warmer than the 20th-century norm for July.

This follows the warmest 12-month period ever recorded in the United States, and it continues a long-term trend that is obvious to all except those who stubbornly close their eyes: Of the 10 hottest years on record, nine have occurred since 2000.

James E. Hansen, who heads NASA's Goddard Institute for Space Studies, summed it up in a piece he wrote for The Washington Post last week: “The future is now. And it is hot.” Hansen wrote that when he testified before Congress in 1988 and painted a “grim picture” of the consequences of climate change, he was actually being too optimistic. His projections of how rapidly temperatures would rise were accurate, he wrote, but he “failed to fully explore how quickly that average rise would drive an increase in extreme weather.”

Yes, scientists are finally asserting a direct connection between long-term climate trends and short-term weather events. This was always a convenient dodge for climate-change deniers. There might be a warming trend over decades or centuries, they would say, but no specific heat wave, hurricane or hailstorm could definitively be attributed to climate change.

“To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change,” Hansen wrote. “The deadly European heat wave of 2003, the fiery Russian heat wave of 2010 and catastrophic droughts in Texas and Oklahoma last year can each be attributed to climate change.”

Hansen went on, “The odds that natural variability created these extremes are minuscule, vanishingly small. To count on those odds would be like quitting your job and playing the lottery every morning to pay the bills.”

The other escape hatch for deniers is the question of why the Earth's atmosphere is warming. Yes, there may be climate change, this argument goes, but we know there have been ice ages in the past and other big temperature variations. What we're witnessing is due to natural processes — perhaps some long-term cycle we are too feeble to comprehend. You can't prove that human activity, specifically the burning of fossil fuels, is to blame.

University of California at Berkeley physicist Richard Muller, one of the leading skeptics on climate change, has reversed field and announced that his research indicated the atmosphere is warming rapidly. Last week, Muller announced in The New York Times that “I'm now going a step further: Humans are almost entirely the cause.”

We can't do anything about the greenhouse gases we've already spewed into the atmosphere, but we can minimize the damage we do in the future. We can decide what kind of environment we leave to our grandchildren. I'd like to hear President Obama and Mitt Romney talk about the future of the planet. What about you?