January is the vanguard of climate change in the US

map mean temperature anomalies january 2014

Mean temperature anomalies for the continental US from January 1-26 (courtesy of the National Weather Service).

It’s been freaking cold in the Eastern half of the US, and it’s only gotten colder in the past 12 hours or so.

Another section of the dreaded Polar Vortex has broken off and is hovering over the Midwest. This morning, temperatures hovered around -9°F in Cleveland, just shy of the record low for the date. Further inland, however, temperatures plummeted to -14°F or lower.

There’s no question that this January has been abnormally cold and snowy for the region. Through yesterday, the average temperature this month was 22.6°F, which is 5.4°F below the long-term average of 28.1°F. The only way for the monthly temperature to reach that mark would be if the next 5 days were, on average, 63°F. Given that it’s currently 5°F and tomorrow’s high will be 12°F, that isn’t going to happen.

Yet, by most regards, this January has been far from record-breaking in Northeast Ohio. To date, it is only the 16th coldest January since 1964, and the temperature anomaly is not statistically significant (for fellow nerds, the z score is -0.723). Furthermore, just 5 years ago in 2009, the average monthly temperature for January was 19.4°F, the third coldest on record.

But, as we know, one cold month or even winter does not a trend make; the world is warming steadily. And, in the US, January has warmed at a faster rate than any other month. It has been the vanguard of warming.

From 1970-2013, January warmed by a rate of 1.14°C per decade, nearly twice as fast as any other month. [Interestingly, this trend does not hold worldwide. October, which has the lowest rate of warming in the continental US, has warmed at the greatest rate (0.33°C per decade) globally. This result is likely due to the fact that global temperatures include data from both sides of the equator.]

monthly average temperature anomalies

Monthly average temperature anomalies for the United States for 1970-2013 (Data from NOAA National Climatic Data Center).

Cleveland has followed a similar trend. Over the last 50 years, January has demonstrated the greatest rate of warming, with average monthly temperatures increasing by 1.371°F per decade. This number is nearly two-thirds larger than second-place February, which has warmed at a rate 0.826°F.

cleveland monthly temperature anomalies

Monthly average temperature anomalies for Cleveland from 1970-2013 (data from Northeast Ohio Media Group).

Moreover, the number of days on which temperatures dip below 10°F has fallen steadily during this period, decreasing by 2.31 days per decade. This winter has clearly bucked that trend, as there have already been 12 days below 10°F since the beginning of December. That’s the most since we had 15 such days in 2009, and we aren’t even into February yet.

number of frigid nights in cleveland

The number of frigid nights in Cleveland per year, 1970-2013 (courtesy of Climate Central).

Interestingly, for as far below average as temperatures have been in the Midwest, they’ve been even higher than average throughout the West. While mean temperatures have been 4-5°F below average throughout much of the country, nearly all of California, Montana, and Nevada have seen temperatures upwards of 8-9°F higher than normal. This disparity doesn’t even account for Alaska’s abnormally warm winter weather. Fairbanks, for instance, has been three times warmer than normal this January.

Climate change deniers have consistently tried to use the cold snap blanketing most of the eastern US as evidence that, as noted climatologist Donald Trump put it, global warming is “bulls#*t.” Cold weather in January doesn’t disprove climate change. In fact, January has been the proverbial canary in the coal mine for global warming, and that trend hasn’t changed in the last 28 days.

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