|Above: Departure of surface temperature from average for December 28, 2017. Areas in red and orange are not necessarily warm, but they are above the average for this time of year at that location. While the Northeast U.S. was experiencing near-record cold, the globe as a whole was 0.5 °C above average, thanks to global warming. Image credit: ClimateReanalyzer.org, University of Maine Climate Change Institute.|
Are we safe to ignore global warming because it’s cold outside? In a tweet published on December 28, President Donald Trump wrote this:
In the East, it could be the COLDEST New Year’s Eve on record. Perhaps we could use a little bit of that good old Global Warming that our Country, but not other countries, was going to pay TRILLIONS OF DOLLARS to protect against. Bundle up!— Donald J. Trump (@realDonaldTrump) December 29, 2017
Indeed, some parts of the eastern U.S. are expecting bitter, record-breaking cold for New Year’s Eve. Unfortunately, this doesn’t mean human-produced climate change is something we’ve put behind us.
The United States is not the world. The eastern U.S. occupies less than 1% of the world’s surface. Most of the planet is expected to be warmer than average over the next few days. But the coldest departures from average will be located over the eastern United States and Canada, so it’s easy to focus on that one part of a much bigger picture.
Climate change doesn’t get rid of weather. We can still expect cold waves and heat waves, even as greenhouse gases make our overall climate warmer over time. And since global warming doesn’t change the fact that Earth is tilted on its axis, winter still happens.
This has been one of the warmest years in U.S. history. For January through November, this year’s average U.S. temperature was the third warmest in records going back to 1895. The only warmer years (for Jan.-Nov.) were 2012 and 2016, according to NOAA. As of Dec. 24, NOAA reported more than 33,000 daily record highs this year, but only about 9000 daily record lows.
Climate change may be raising the odds of winter cold waves in the eastern U.S. Several groups of scientists have found that warming in the Arctic and the resulting loss of sea ice are making it more likely that the jet stream will take dramatic wintertime dips and push intense cold outbreaks into midlatitude areas, such as the eastern U.S. These cold waves aren’t enough to compensate for the overall warming of the climate across the whole planet.
Not all of the U.S. will be colder than normal on New Year’s. Temperatures will be above average for most of the 50 million Americans who live in the Southwest. Las Vegas, Phoenix, and Albuquerque will each get within a few degrees of their warmest New Year’s Eve on record. The unusually warm, dry weather of early December fed into the catastrophic wildfires that struck Southern California. Meanwhile, Alaska is having one of its mildest Decembers on record, causing problems for transportation.
Two weeks do not a winter make. Most of December was warmer than average over the central and eastern U.S. Looking ahead, NOAA’s 3- to 4-week temperature outlook calls for above-average temperatures to prevail across much of the nation in mid- to late January.
Jeff Masters contributed to this post.