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Posted at 01:18 PM ET, 07/10/2012

NOAA scientist: 80 percent chance recent heat records due to climate change

Is climate change giving our weather just a little nudge to make setting heat records - like Washington, D.C. just experienced - vastly more likely? That’s the opinion of one NOAA scientist.

Meet Martin Hoerling, a research meteorologist at NOAA’s Earth System Research Laboratory. I recently participated with him and several other climate scientists in a Google Hangout conversation.

What Hoerling had to say about climate change and record-setting temperatures was fascinating. He makes a compelling case that human-caused climate change isn’t causing heat waves, but - in many instances - adding to their intensity. Consider these excerpts from his commentary, about 34-38 minutes into the 60 minute panel discussion.

“....the globally averaged temperature of the planet has risen beyond any doubt beyond where you would expect ... with natural variability alone...”

. . .

“... [O]n the heat wave story. Sometimes you’ll see ‘that heat wave was due to climate change’ That’s not a very accurate statement, not a very helpful statement. But it’s not entirely untrue either.”

Above: Google hangout to discuss climate change and severe weather. Stanford Professor Noah Diffenbaugh is joined by Harold Brooks of the NOAA National Severe Storms Lab, Martin Hoerling of the NOAA Earth System Research Lab, Angela Fritz of Weather Underground, Dave Metz of the FM3 opinion research firm, and Jason Samenow of the Washington Post.

. . .

“It may well be that 90 percent of [a given] heat wave was natural, but that the 10 percent that pushed it to record proportions was due to climate change.”

“There’s a certain chance that ... a daily maximum temperature record is going to be set any place any given day...”

“. . . [Presently] we’re breaking high temperature records much more frequently than by chance. And, by some estimates, the ratio of that exceedance of breaking highs compared to what you would expect by chance would lead to us say to that there’s about an 80 percent chance that the record high you experienced was due to climate change.”

“That’s a very nuanced statement when you start thinking about it but it’s a very interesting statement. It speaks to the power at which climate change is operating.”

“A heat wave itself - most of it is due to natural variability. But that extra little step to record proportions pushing over a prior threshold is what climate change is doing. It’s adding an edge to that heat wave.”

How confident is Hoerling in his statement that there’s an 80 percent chance record highs being set are due to climate change?:

“[It’s] a strong statement and a defensible scientific statement,” he said.

Consider Hoerling is no climate change alarmist. An expert on detection and attribution of climate change, Hoerling has even been criticized by peers and bloggers for being too conservative in connecting the dots between climate change and extreme weather.

As such, what Hoerling is claiming about heat records and climate change is not controversial in the climate science community. A joint study by UK Met Office and NOAA scientists published today draws similar conclusions about this link.

The study, “Explaining extreme events of 2011 from a climate perspective” (PDF), notes for example, climate change is increasing the odds of La Niña-related heat waves like the one that occurred in Texas last summer. It found a heat wave of the intensity of last summer is about 20 times more likely now compared to the 1960s.

It also describes how climate change altered the odds of recent weather experienced in the United Kingdom. It examined very warm weather that occurred in the UK in November 2011 and very cold weather in December 2010 and possible connections to climate change. NOAA summarizes its findings:

“In analyzing these two very different events, UK scientists uncovered interesting changes in the odds. Cold Decembers are now half as likely to occur now versus fifty years ago, whereas warm Novembers are now 62 times more likely.”

Whereas scientists are making advances in linking climate change and extreme weather, the NOAA/UK Met Office study cautions: “Currently, attribution of single extreme events to anthropogenic climate change remains challenging.”

But the study also notes considerable progress has been made in this area of research, and it’s not unreasonable to link certain weather events and climate change provided percentages or probabilities are used to characterize any connection.

Linking climate change and heat wave intensity is less controversial than linking climate change and the intensity of precipitation extremes. The study found that in some cases, extreme weather occurred with no apparent link to climate change. For example, no strong connections was identified between climate change and the devastating Thailand floods of 2011.

A key conclusion of the NOAA/UK Met Office study reads accordingly:

While much work remains to be done in attribution science, to develop better observational datasets, to improve methodologies, to make further progress in understanding and to assess and improve climate models, the contributions in this article demonstrate the potential that already exists for meaningful assessments of the connection between specific extreme weather or climate events that occurred in a particular year and climate change.

By  |  01:18 PM ET, 07/10/2012

Categories:  Latest, Climate Change, Extreme Heat

 
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