Cold Nights Are Decreasing Across the U.S.

http://www.climatecentral.org/news/cold-nights-decreasing-across-us-18587

Jan. 23, 2015

It’s easy to think of global warming as something that happens at a steady pace everywhere. But that’s not the full story. It’s true that the global average temperature has been rising overall since modern record-keeping began, and it’s true that 2014 was the hottest year on record, but the rise hasn’t been perfectly steady. Each year isn’t always warmer than the one before, and some places — the Arctic, for example — have warmed faster than others.

When you zoom in, even regions in the U.S. have warmed at different rates. Some seasons have warmed faster than others. And the pace of warming can even vary depending on the time of day. For example, a Climate Central analysis in 2013 showed that winter nights in the U.S. have warmed about 30 percent faster than nights over the entire year.

Now we've done a new city-level analysis showing the trend in daily low temperatures below freezing. That is, for most of the country. In places where the temperature dips below freezing so rarely that it's hard to establish a trend at that cutoff, we used 40°F or 45°F. You can find your city in the dropdown menu above to see how cold nights have changed since 1970.

Of course, daily lows don’t always happen at night but they usually do. And the rise we see in daily lows is consistent with the overall pattern you’d expect in a warming world. Due to regional variability, the lows haven’t been on an upward trend in every city — but that’s just one more example of how global warming can have a distinctly local flavor.