Last week on his radio show, Rush Limbaugh began to dig a hole for himself when, in a bid to cast doubt on global warming, he postulated that the heat index was “manufactured by the government.” He then alleged that the heat index was “playing games with us” and that other media outlets were being sucked in by the artificial heat index numbers. Despite ridicule and debunking by meteorologists, Limbaugh decided he would continue his digging.

He told his audience that, in Boston, temperatures one day fell short of breaking the record set back in 1926 by one degree. To Rush, this proved that “there is almost nothing true in mainstream, drive-by media” and all their reports, including weather, are to “advance a political agenda of liberalism.”

And then Limbaugh dug even deeper. Yesterday, he suggested that the reason people believe in global warming is because air conditioning use has increased over the past 30 or 40 years and people therefore feel hotter than they used to feel when they step outside. He claims “it's all about the baseline you're using for comparison.”

LIMBAUGH: I have a theory about global warming and why people think it's real. Go back 30, 40 years when there was much less air conditioning in the country. When you didn't have air conditioning and you left the house, it may in fact have gotten a little cooler out there, because sometimes houses become hot boxes. Especially if you're on the second or third floor of a house in the summer time and all you've got is open windows and maybe a window fan. Or you have some servant standing there fanning you with a piece of paper. When you walked outside, no big deal, it's still hot as hell. Now, 30, 40 years later, all this air conditioning, and it's a huge difference when you go outside. When you go outside now, my golly, is it hot. Oh. Global warming. It's all about the baseline you're using for comparison.

Limbaugh is utterly denying the scientific facts that surround global warming. Suggesting that the use of air conditioning over the past few decades is causing merely the perception of global temperature increase is preposterous. In fact, virtually every dataset used to measure global temperature confirms a warming trend on a global scale.

This graph shows global temperature data derived from satellites (for lower atmosphere rather than surface) by both the University of Alabama at Huntsville (UAH) and by the research firm Remote Sensing Systems (RSS), dating back to 1979 when the first satellite information is available. The chart also plots data from the three primary global surface temperature datasets. The black line is an average of all five records.

[Climate4you.com, accessed June 2011]

His global warming theories are consistently out of touch with reality, yet they appear to be in tune with others in the right-wing media. Sadly, Limbaugh is not alone in downplaying the extreme heat wave that hit the United States. It has yet to be seen, however, whether others will echo his air conditioner theory.

Media Matters intern Shayna Gilmore contributed to this blog post