May Was Earth's Second-Warmest in 137 Years; Only 2016 Was Hotter

Chris Dolce
Published: June 15, 2017

May 2017 was the second-warmest May since records began 137 years ago, topped only by the all-time high mark that was clinched last year.

NASA's Goddard Institute for Space Studies calculated the Earth's mean temperature over land and water in May was 0.88 degrees Celsius above the 1951-1980 average, second only to May 2016's 0.93 degree Celsius departure from average. May 2017 beat out May 2014 by just 0.01 degrees Celsius for the second-place ranking.

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Graphic of monthly global surface temperature anomalies from 1880 through 2017, color-coded by year, in degrees Celsius, relative to 1980-2015 average. (NASA)

This is the fifth month so far this year to rank among the top three warmest on record for each respective month. February, March and April 2017 ranked as second-warmest, while January 2017 finished in third place.

The largest May warm temperature anomalies were in western Europe, northern Africa, Asia, eastern South America, northern Alaska, northern Canada and near Antarctica. Northern Russia was the most significantly cooler-than-average location.

These temperature anomalies may not sound like much, but in the realm of global monthly temperatures, they are very significant.

Since April 2014, 35 of 38 months have tied or surpassed the third-warmest respective month in NASA's database. Sixteen of those months either tied or set new respective monthly records, including 11 straight months from October 2015 through August 2016.

May 2017 temperatures compared to average. Darker orange and red areas were the farthest above average. (NASA)

May 2017 marked 382 months since the last colder-than-average month in NASA's database – July 1985.

The last three consecutive years – 2014, 2015 and 2016 – each set a new warm record for the globe, according to NASA.

What's ultimately most important is not whether a given month is a fraction of a degree warmer or colder; rather, it's the overall trend, which continues its upward climb since the late 1970s.

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