You may remember headlines like these last summer:
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With Blow-Out March Heat Wave, Meteorologist Masters Says ‘This is not the atmosphere I grew up with’
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The 2012 Heat Wave: “Almost Like Science Fiction” | Popular Science
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Record Heat Wave Pushes U.S. Belief in Climate Change to 70%
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US heatwave may have been made more likely by global warming …
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Global Warming May Have Fueled March Heat Wave Odds
A new paper by a team of NOAA scientists published in the Bulletin of the American Meteorological Society finds that the US extreme heat wave of March 2012 was due to natural variability, not AGW. According to the authors, “Several lines of evidence strongly implicate natural variations as the primary cause for the extreme event,” and “We conclude that the extreme warmth over the central and eastern U.S. in March 2012 resulted primarily from natural climate and weather variability, a substantial fraction of which was predictable.”
They go on to show how synoptic scale weather forecasting models like GFS predicted the event, indicating it was a “weather, not climate” event. Now that the analysis says ‘natural variability”, will there be followup headlines? Doubtful. News of “normalcy” doesn’t sell, hype and sensationalism does. However, I’m going to take this opportunity to call out Climate Central’s Andrew Freedman, who is one of the more reasonable people who sensationalized the event, to post a follow up to his collection of stories on it here.
The full paper is below.
The Making of An Extreme Event: Putting the Pieces Together
Randall Dole 1, Martin Hoerling 1, Arun Kumar 2, Jon Eischeid 1,3, Judith Perlwitz 1,3, Xiao-Wei Quan 1,3,George Kiladis 1, Robert Webb 1, Donald Murray 1,3, Mingyue Chen 2, Klaus Wolter 1,3, and Tao Zhang 1,3
1 NOAA Earth System Research Laboratory, Boulder, Colorado 2 NOAA Climate Prediction Center, Camp Springs, MD 3 University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, Colorado
Abstract
We examine how physical factors spanning climate and weather contributed to record warmth over the central and eastern U.S. in March 2012, when daily temperature anomalies at many locations exceeded 20°C. Over this region, approximately 1° C warming in March temperatures has occurred since 1901. This long-term regional warming is an order-of-magnitude [10 times] smaller than temperature anomalies observed during the event, indicating the most of the extreme warmth must be explained by other factors. Several lines of evidence strongly implicate natural variations as the primary cause for the extreme event.
The 2012 temperature anomalies had a close analogue in an exceptionally warm U.S. March occurring over 100 years earlier, providing observational evidence that an extreme event similar to March 2012 could be produced through natural variability alone. Coupled model forecasts and simulations forced by observed sea surface temperatures (SSTs) show that forcing from anomalous SSTs increased the probability of extreme warm temperatures in March 2012 above that anticipated from the long-term warming trend.
In addition, forcing associated with a strong Madden-Julian Oscillation further increased the probability for extreme U.S. warmth and provided important additional predictive information on the timing and spatial pattern of temperature anomalies. The results indicate that the superposition of a strong natural variation similar to March 1910 on long-term warming of the magnitude observed would be sufficient to account for the record warm March 2012 U.S. temperatures.
We conclude that the extreme warmth over the central and eastern U.S. in March 2012 resulted primarily from natural climate and weather variability, a substantial fraction of which was predictable.
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Full paper (draft revision submitted) is available here:
Click to access Making_Extreme_Event_revised_04_12_13.pdf
h/t to The Hockey Schtick
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Andrew Freedman’s Guardian article actually quoted Randall Dole, who is the lead author of the new study:
As to whether global warming might be contributing to the recent hot wave, Randall M. Dole, a deputy director of research at NOAA’s Earth System Research Laboratory (ESRL) in Boulder, Colo., said, “Absolutely. The planet as a whole is warming, the continents on average are warming faster than the oceans, so there is a great body of scientific evidence that would support such an interpretation. The question is how much.”
” . . . It’s hard to attribute more than a modest fraction of the event magnitude to [manmade climate change] itself. It could well have made a truly extreme event even warmer,” Dole said.’
That’s pretty much what the new paper says.
“Overall, our results indicate that the extreme magnitude of the March 2012 temperature anomalies can be largely explained by natural variability, with an additional contribution from a long-term warming trend of approximately 1°C that is likely due mostly to human influences.”
Freedman presented Dr Dole’s view as in line with his article, and I think it is. It’s just saying that the meteorological causes were superimposed on a 1° rise. This is a small part of the heat wave excess, but not nothing. That’s the standard scientific view of the effect of AGW on extreme events. Heat waves aren’t different, just apt to be a bit hotter.
Nick Stokes:
Since we’re discussing the US, actually the SE US has actually been cooling since the start of the 20th century. See this.
In particular, the Chicago region has had near neutral temperatures over that period, so AGW could not have played a role in their local temperature extremes.
You also need to look at trends in daytime high temperatures, rather than mean temperatures, since that is what is relevant for “tagging AGW onto high temperature extremes”.
Carrick,
” SE US has actually been cooling since the start of the 20th century. See this.”
You’ve shown a map of June trends. But this was a March heatwave. The March trend map shows a rise pretty much in line with the paper’s 1°’C.
Good catch. I was thinking summertime weather..
Here’s March.
I don’t see Chicago at 1°C there either. You have to go outside of the affected region to find a 1°C increase. And again, this is (tmax + tmin)/2, and I’d expect the trend in maximum temperature to be smaller than what’s shown here.
I’d rate this as a case where AGW contributions aren’t very important, if present at all, in the observed extreme weather.
NOAA: Another ‘AGW caused heat wave’ is actually just natural variation
Not according to the paper cited.
That would seem to be in line with the mainstream view. Heatwaves will still happen, but the underlying long-term warming will make them hotter. The articles from last year don’t diverge from this view either. Quoting some of them (The Pop Science link is wrong),
“Having an influence”
“Natural variability… key role”
What is the controversy here?
barry,
As Jeff Glassman points out above:
“…to the extent that AGW exists, it is not measurable. What would be news is the first bit of evidence of the existence of AGW.”
CO2 may cause some minor global warming. But at current concentrations it is too small to measure, so you are getting your knickers in a twist over something so minor that it can be completely disregarded as inconsequential.
Don’t you have anything better to do?
If you’re at a loss as to something constructive to do, may I suggest writing comments on various blogs attacking the anti-environment, anti-wildlife, bird-chopping windmills we see going up everywhere? That would certainly be a lot more productive than endlessly arguing about something that is too small to even measure.
Also, the NOAA position you quoted is nothing but their opinion; their belief. There is NO verifiable, testable, measurable, quantified AGW occurring. NOAA is simply speculating, and they should label it as such.
It comes from the same paper Anthony quoted to make his point in the article. All I’m showing is that it is consistent with last year’s views, contrary to the headline above.
“NOAA: Another ‘AGW caused heat wave’ is actually just natural variation”
Really, Anthony?
Near as I can see, the scientists a year ago thought that the heat was was natural variation plus a bit of AGW (although they carefully stated that analysis needed to be done to confirm that). Well, now that the studies have been done, the scientists now think {{{ drum roll }}} that the heat was was natural variation plus a bit of AGW.
It is one thing to argue the relative merits of AGW — there are lots of issues there that are clearly up for debate. It is another thing altogether to leave out one key point from the earlier reports and leave out the opposite key point from current reports, and then say the two have opposite conclusions.
If storm, hurricane, and heat wave frequency are within historical norms, how does “more likely” manifest?
I think we have a new definition of likely.
This is professional baffle-gab.
Reblogged this on CACA and commented:
NOAA found 2012 US drought not caused by global warming. Now Obama’s same Govt agency finds 2012 heat-wave not caused by anthropogenic climate change?!
Phone line busy, both times when Obama dialled NOAA for updates or…?!