Despite an unusually chilly Arctic, and El Niño’s absence, July 2017 tied for warmest such month on record

By Tom Yulsman | August 16, 2017 11:22 am

That makes last month one of the warmest our planet has experienced since record-keeping began in 1880

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This graph shows how each month since 1880 has varied from the annual mean for the entire globe. The curve shows the seasonal cycle, with the warmest temperatures occurring during summer in the Northern Hemisphere. July 2017 tied with July 2016 for the second warmest such month on record — and was one of the warmest months in the record overall. (Source: NASA GISS)

Up in the high north, it was unusually cool last month. And unlike last year, there was no El Niño to help amp up temperatures for the globe overall.

Yet July 2017 was in a statistical tie for warmest such month in 137 months of record keeping, according to the monthly climate, according to a monthly analysis of global temperatures by scientists at NASA’s Goddard Institute for Space Studies.

July 2017 was 0.83 degrees Celsius warmer than the mean July temperature for the 1951-1980 period. Only July 2016 showed a similarly high temperature — 0.82 °C.  All previous July’s were more than a tenth of a degree cooler, according to NASA.

The graph above allows us to visualize not only how July 2017 stacked up to previous July’s but also all other months. It shows how each month since 1880 has varied from the annual mean for the entire globe.

The result is a visualization of the seasonal cycle, with summer in the Northern Hemisphere naturally being the warmest months (for a reason I’ll get to in a minute). As the graph shows, July 2017 and July 2016 were second only to August of last year as being the very warmest of all 137 months in the record.

Why is summer in the Northern Hemisphere naturally warmer than summer in the south? There’s much more land compared to ocean in the north. And land absorbs and releases heat much more quickly than water. So the greater amount of water in the south tends to tamp down wide, seasonal temperature swings, at least when looking at the hemisphere as a whole.

July’s anomalous heat is quite surprising for a couple of reasons. The first is seen in this animation of two global maps:

Source: NASA GISS

Source: NASA GISS

The two maps in the animation show how temperatures have compared to the long-term mean during two different periods. In one map, I’ve shown how things looked last month. Note the blue temperatures in the Arctic, indicating that temperatures up north were mostly cooler than normal in July 2017. Meanwhile, in most other regions, anomalous warmth was the norm.

The second map shows how the globes temperatures varied from the long term mean on an annual basis from 2012 through 2016. I chose this five-year period to smooth out month-to-month variations and show a longer-term pattern. Note the reds up north, indicating that over that longer-term period, the Arctic has been considerably warmer than any other region.

In fact, over the long term, the Arctic has been warming twice as fast as the rest of the globe.

The Arctic chill should have helped temper the overall global picture in July. But quite surprisingly, it did not.

And then there’s the other surprising factor. During July of last year, global temperatures received a significant boost from El Niño. But El Niño and its after-effects are now long gone. Yet even without a boost, last month still managed to tie with July of 2016.

This is clearly a testament to the continuing impact of human-caused warming on our planet.

Where might 2017 as a whole wind up?

The Tweet above shows the prediction from Gavin Schmidt, who heads NASA’s Goddard Institute for Space Studies. Based on 2017’s data through July, it’s quite likely that this year will go down in the record books as second only to 2016 as warmest on record.

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  • Not_that_anyone_cares, but…

    I’ve no doubts about recent climate change and human contributions to green house gasses that are accelerating said climate change.

    But I am really tired of ”on record”.

    That’s it. That is all I came here to say – at this time.

    • Tom Yulsman

      I am definitely open to other ways of expressing that!

    • OWilson

      Take away all that RED stuff, and the graphs using extrerme and inappropriate XY scales that show the record running off the chart, not even enough paper to contain them, and:

      At the bottom of it all you have this:

      “All previous July’s were more than a tenth of a degree cooler, according to NASA”

      (We won’t ask about margins of error or scientific stuff like that! :)

      • Mark R Horne

        You’re cherry-picking one phrase and then twisting it’s meaning.

  • jonathanpulliam

    The miniscule sampling size makes the NASA temperature record numbers statistically insignificant hence meaningless. But you knew that.

    • Mark R Horne

      This is a huge and trending sample with great meaning. Saying otherwise doesn’t make the NASA records any less important. You have argued that satellite records are the only reliable sources of data, yet are unable or unwilling to point out their flaws as well. One of those flaws was recently corrected and the satellite data is much more aligned to the ground and sea-based measurements.

      • jonathanpulliam

        You are confused. I’ll leave it at that.

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ImaGeo

ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.

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