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2013 Record Highs vs. Record Lows

If it seems like you haven't heard much about record high temperatures this year, you're not imagining it. For the first time in 20 years, the U.S. has recorded more record lows than record highs—and that 20-year gap is a major clue that our climate is changing.

Back in the middle of the last century, record highs and record lows pretty much balanced out. Not necessarily in any one year, or even in any one decade, because we will always experience weather extremes. For example, the 1950's saw somewhat more highs than lows before things flipped in the 60's and 70's. Then, they flipped back again in the 80s. But even during that time, individual years also flipped from high to low while the overall number of record highs and lows came out even.

Since the 80s, though, highs have outpaced lows by a bigger margin every decade, and warm records (the combination of high max and high min) have also regularly outpaced cool records (the combination of low max and low min). By in the 2000's, the U.S. set more than twice as many record highs as it did record lows. That's strong evidence that the climate is on a real warming trend, which is what you'd expect from the buildup of heat-trapping greenhouse gases scientists have measured.

Just because the U.S. is warming overall, along with the rest of the world, that doesn't mean we won't have cold snaps like the one currently gripping the country. And it doesn't mean we won't have more years where record lows outpace record highs. But the fact that it hasn't happened more than once since 1993 is something worth noting.