In January, U.S. Saw Vastly More Daily Warm Records Than Cold Records. February, Too.

Feb 21, 2015 by



January saw a coolish (“below average” temperature) North East but, ed a relatively hotter (“much above average”) West Coast. Recent research links this pattern to human-caused climate change.

The U.S. had the 24th warmest January in the 1895-2015 temperature record, sick NOAA reported this week. And we saw four times as many daily warm temperature records as daily cold records. Globally it was the second-hottest January on record.

Yes, medical those of us on the East Coast were cold, but the West Coast was sizzling, as seen in the chart above. NOAA explains that seven Western states — California, Idaho, Nevada, Oregon, Utah, Washington, and Wyoming — “had a top 10 warm January.” But while “parts of the Southern Plains and Northeast were cooler than average… no state had a top 10 cool January.” A new 2015 study links this bifurcated weather pattern to climate change (see below).

Global warming of 1°F since 1950 doesn’t mean the end of winter or the end of record daily low temperatures. It’s still going to be much, much colder on average in January than July — and one of the most iconic indicators of winter for many Americans, northeastern blizzards, is actually going to get worse for the foreseeable future, as climatologists have long explained.

As for daily temperature fluctuations, they are so large at the local level that we will be seeing daily cold records — lowest daily minimum temperature and lowest daily maximum temperature — for a long, long time. That’s why climatologists prefer to look at the statistical aggregation across the country over an extended period of time, since it gets us beyond the oft-repeated point that you can’t pin any one single, local temperature record on global warming.

NOAA reports “during January, there were 3,499 warm daily temperature records broken or tied (1,906 warm maximum and 1,593 warm minimum), compared to 775 cool daily temperature records broken or tied (441 cool maximum and 334 cool minimum).” That’s a ratio of more than 4-to-1.

If you want to know how to judge whether that is a big deal, here’s what a 2009 National Center for Atmospheric Research study found over the past six decades (see “Record high temperatures far outpace record lows across U.S.“):

record daily highs to record daily lows

The ratio of record daily highs to record daily lows at 1,800 weather stations in the lower 48 states from January 1950 through September 2009. Each bar shows the proportion of record highs (red) to record lows (blue) for each decade. The 1960s and 1970s saw slightly more record daily lows than highs, but in the last 30 years record highs have increasingly predominated, with the ratio for the 2000s about two-to-one for the 48 states as a whole.

Interestingly, NOAA also reports the hot and cold records for the month of February through the 18th. It is more than 4800 to 1500, over 3 to 1. Again, cool East Coast, hot West Coast.

As you may recall, in spring 2014, a NASA-funded study directly connected both the cool east and hot west to the same weather “dipole” pattern — and then connected that dipole pattern to global warming pollution.

The news release for that study explained that the research provides “evidence connecting the ampli?ed wind patterns, consisting of a strong high pressure in the West and a deep low pressure in the East [labeled a ‘dipole’], to global warming.” Researchers have “uncovered evidence that can trace the ampli?cation of the dipole to human in?uences.” (In September, NSF-funded research also found that the Western high pressure ridge was “very likely linked to human-caused climate change.”)


The lead author of the 2014 dipole study, Dr. Simon Wang of the Utah Climate Center, emailed me recently that in a new journal article they reexamined their results using 17 of the latest (CMIP5) climate models — and “found the same conclusion” as their 2014 paper.

Rutgers extreme weather expert Jennifer Francis explains the climate science behind this weather pattern in her new essay on “A melting Arctic and weird weather.” In particular, the jet stream appears to be getting weaker and, as a result, wavier. As she notes, her “new work, published last month in Environmental Research Letters, uses a variety of new metrics to show that the jet stream is becoming wavier and that rapid Arctic warming is playing a role. If these results are confirmed, then we’ll see our weather patterns become more persistent.”

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