Extreme warmth has dominated U.S. weather records since 2010. This is climate change.

By Jason Samenow June 1 at 1:42 PM

Temperature difference from normal over Lower 48, January to April 2017. (NOAA)

If it seems as if America’s record heat is in the news much more so than record cold in recent years, it is not a media conspiracy to ignore extremely cold weather. There is a simple and scientifically sound reason for it: Record warmth is happening much more often.

Record-warm weather has occurred five times as frequently as record cold in U.S. cities since 2010, according to a new analysis. The imbalance represents a striking example of climate change affecting the nation’s extreme weather in a clear and tangible way.

Washington is among the cities that has witnessed the most disproportionate record warmth, setting nearly 15 record highs for every record low.

Reno, Nev., and Phoenix lead the pack of cities sizzling much more often than shivering, setting around 24 and 19 record highs for every historically low mark.

(Adapted from Christopher Burt, Weather Underground)

These shifts toward more extremely warm temperatures are being seen all across the nation, from California to New York and from Texas to Michigan.

Not one of the 60 cities and towns analyzed experienced more records for cold weather than warm.

Weather historian Christopher Burt conducted the analysis and reported these findings on Category 6, the blog at Weather Underground, on Tuesday.

For his analysis, Burt examined temperature readings in cities and towns spread more or less evenly across the Lower 48 and analyzed data from Alaska and Hawaii.

Sites chosen for extreme=temperature analysis. (Christopher Burt, Weather Underground)

He then counted how many record-high and -low temperatures were set at each location since 2010 and calculated the corresponding ratio. For example, if a location experienced 20 record highs and five record lows, the ratio would be 4 to 1 or 4.0.

Here are some interesting nuggets from Burt’s analysis:

• Tampa set the most record highs: 210, averaging more than two per month during the analysis period.
• Grand Junction, Colo., logged the most reports of record lows, 51, but still substantially fewer than its 85 record highs.
• The locations with the smallest ratio of record highs to record lows were Eureka, Calif. (1.18), Kansas City (1.40) and Grand Junction (1.67).
• Record highs vastly outnumbered record lows in Alaska and Hawaii.
  • Fairbanks, Juneau and Nome had three to four record highs for every record low, but Barrow — Alaska’s northernmost town — had a remarkable 66 record highs for every record low (a total of two).
  • Both Honolulu and Lihue set around 15 record highs for every record low.

Particularly in city locations, it is likely that urbanization has contributed to the marked increase in record-warm weather, in addition to climate warming from rising greenhouse-gas concentrations.

However, Burt included some locations outside of cities in his analysis — revealing that disproportionate increases in record-warm weather is occurring there, too. “I also made a point of including some small towns in significant geographical locations such as Cape Hatteras, North Carolina, and Glasgow, Montana,” he wrote. These locations posted four to six times as many record highs as record lows.

If the climate was not changing, we would expect to see roughly even numbers of record highs and lows in all locations, and that has not even been close to the case in recent decades.

Burt’s results are supported by peer-reviewed published studies, most notably work performed by Gerald Meehl at the National Center for Atmospheric Research.

In 2009, Meehl published a paper that found about twice as many record highs as record lows were set in the United States during the first decade of the new millennium.

Meehl’s latest study, published late last year, projects that by later this century, heat records could outnumber cold records by a factor of 15.

Guy Walton, a meteorologist who previously worked at the Weather Channel, has found that record-high temperatures have outnumbered record lows in the Lower 48 for 29 straight months (from December 2014 to April 2017). No previous streak has been this long. (The next-longest streak, of 19 months, occurred March 2011 to September 2012, Walton found.)

At the same time, the nation has witnessed its warmest one-, two-, three-, four- and five-year periods in 122 years of record-keeping, according to the National Oceanic and Atmospheric Administration.