Ecocentric

Climate Change Equals Hot Summers. Case Closed.

An unusually explicit climate scientist drops the hedging and says what more and more people believe

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Spencer Platt / Getty Images

A man pushes a cart of bottled water during warm weather in New York City on July 6, 2012

Every time a major heat wave, drought or hurricane occurs, journalists call up climate scientists to ask if global warming is the cause. Nearly every climate scientist has the same stock response: while global warming can make extreme events more likely or more powerful, we can’t say climate change is causing that string of 100°F days or that Category 5 hurricane. This includes other extreme events like the severe dryness that has left more than three-fifths of the continental U.S. in some form of drought. Sure, we can expect more heat waves and extended dry periods in a global-warming future, but no reputable scientist would say that what’s exceedingly likely to unfold over time is directly responsible for what’s happening in 2012.

But James Hansen is different. The NASA climate scientist is one of the world’s foremost global-warming researchers, and almost certainly its boldest. It was Hansen who testified before Congress on climate change during the landmark hearings in 1988 — during another hot, dry summer — warning of the risks of man-made greenhouse gases. And it was Hansen who, over the past several years, has embraced the role of the scientist-advocate: marching in protests against the proposed Keystone XL oil sands pipeline, calling for a carbon tax as a way to cut greenhouse-gas emissions and authoring the popular science book Storms of My Grandchildren. Hansen has no reluctance to speak out about why man-made climate change is so dangerous — and how it should be fixed.

(PHOTOS: Summer Heat Wave Roasts the Midwest, Northeast)

So it shouldn’t be surprising that Hansen is willing to go further than most of his colleagues in tying extreme weather to global warming. In a new study published in the Aug. 6 issue of Proceedings of the National Academy of Sciences, he uses relatively straightforward math and analysis to reach an explicit conclusion: the recent extreme heat and drought of the sort that has sacked much of the U.S. is so unusual that the only thing that could be causing it is man-made climate change. No hedging, no yes-but, no cautious qualifying.

“Our analysis shows that it is no longer enough to say that global warming will increase the likelihood of extreme weather and to repeat the caveat that no individual weather event can be directly linked to climate change,” Hansen wrote in an op-ed in the Washington Post last weekend. “To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change.”

(LIST: How Hot Can It Get? The 10 Hottest Places in the U.S.)

Hansen and his team looked at the recent past — rather than trying to model the future — to see if they could find the signature of man-made climate change through day-to-day and season-to-season weather. They used the period of 1951–80 as a base because it was a meteorologically stable stretch that also had a wealth of global weather data, unlike earlier periods. During that time period, extremely hot summers — like the one much of the U.S. is experiencing now — occurred only in 0.1% to 0.2% of the globe in a given year. But since 1981, extremely hot summers have baked about 10% of the earth’s land area annually — and in recent years, that percentage has been even higher.

That means the odds of experiencing an extreme summer have risen from 1 in 300 during the 1951–80 period to nearly 1 in 10 now, according to Hansen’s calculations. “I don’t want people to be confused by natural variability,” he said in a statement. “We now know the chances these extreme weather events would have happened naturally — without climate change — is negligible.”

(MORE: The Great Drying Strikes Again)

Hansen’s math isn’t new, but he is much more willing to connect — in a peer-reviewed paper — extremely high temperatures to climate change instead of more natural weather phenomena like the El Niño and La Niña oscillations. Hansen also argues that global warming has made the climate more variable: while extremely hot weather is more likely to occur during the summer, about 15% of the summers over the past 30 years have actually been cooler than the 1951–80 average. To take the title from a new book by the nonprofit Climate Central — which includes the work of TIME contributor Michael D. Lemonick — what we may be experiencing is as much “global weirdness” as global warming.

For the public, the details of fingerprinting extreme-weather events may matter less than the fact of heat and drought itself. And this summer’s outlandishly tough weather — I’m beginning to expect that Oklahoma will simply burst into flames one of these days — is clearly having more of an impact on public opinion than a scientific paper ever could. A recent study found that for every 3ºF that local temperatures had risen above the norm in the week before a survey on climate change, belief in climate change rose by 1%. A July study by the University of Texas found that 70% of Americans surveyed believed the climate was changing, up from 65% in the cooler months of March. If there’s one thing we can take from Hansen’s work, it’s that those temperatures are more and more likely to hit extremes in the years to come, which means belief in climate change should continue to rise as well. Now we just need to do something about it.

PHOTOS: Extreme Heat: 10 Worldwide Spots with Tough Temperatures

84 comments
BrentWalker
BrentWalker

Try the sun.

Go back to the late 18th C and early 19th C and you will see similar climatic events. Look at the sunspot records based on the same methodology as Wolfer system at that time and you will see the current cycle of the sun is mimicking or possibly even lower activity than solar cycle 5 (late 17th early 18th C). We called them little ice ages back them but they were actually extreme weather periods.

Google Astrometria project on the Russian/u/Ukrainian section of the International Space Station. Read what Abdussamatov has to say. You have been hoodwinked into believing that we are to blame. The evolutionary forces that continue to shape our solar system and galaxy are infinitely greater.

S.F.Canyon
S.F.Canyon

typical liberal bull$hit...'nuff said! This is why the best use I can find for this publication is to line a pigeon cage....

Talendria
Talendria

It's willfully ignorant to think that humans have no effect on the ecosystem.  History offers numerous examples of how land and water management can change local weather phenomena, often for the worse.  Unfortunately, no one has developed a weather model that is sophisticated enough to predict the changes, and forestalling these changes would require a sea change in our behavior.

realheadline
realheadline

Hansen should just blame the weather on the witch next door, then sacrifice a chicken or two. His current fortune-telling is the most unscientific nonsense yet. Read what his own colleagues say about his activism ...Err... science. He is a Charlatan and may very well be in violation of the Hatch act. Shame on Time magazine for repeating the lies.

GOPvictory
GOPvictory

So why is it Europe is cooler and wetter than usual this summer? Oh by the way, what happen to all the record amount of tornadoes to be expected in July?

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Gary McCray
Gary McCray

As it continues to get hotter, dyer, more droughts and more bad weather and eventually we get famines and mass death from the lack of food caused by the heat and drought, will you believe it then.

Or will you simply say it's not our fault, God did it.

Just for the record, God didn't do it, we did.

nonpolitical
nonpolitical

 Extreme weather can be expected but the reason is found mostly in sun-activities or lack of activities. It cycles! It is definitely not man made. "God" did it! :-)

JohnDonohue
JohnDonohue

Did you make these statements based on plus/minus? If so, the minus must be really really really bad, since a somewhat warming world, perhaps the last until the next glaciation, will definitely have plus factors, such as vast areas of the north that cannot be farmed now, but which will during this bump up. Also, with all the sea ice melted, the shipping lanes across the North Polar Seas will bring gigantic advantage. Nations are already jockying for ownership of new seabed mineral rights that will open up.

Orson Olson
Orson Olson

"Hansen...uses relatively straightforward math and analysis to reach an explicit conclusion: the recent extreme heat and drought...could be causing it is man-made climate change. 

Actually, this is not "straightforward" but dumb: first, the US is not the globe in "Global Warming," which by the best and most accurate measures (ie, satellite) has not been warming for 10 to 15 years. Second, if later 20th century warming is compared with the mid-20th century cooling, you would expect to find warming patches. This is a circular natural fact, nothing uniquely causal about it. Thus, at best, Hansen offers another guess without any scientific merit supporting a positive (ie, man-made CO2 caused it) conclusion. 

my conclusion? Brian Walsh needs an intro stats course refresher, especially "How To Lie With Statistics."

nonpolitical
nonpolitical

Kevin. Exactly - change does not imply global heating nor man made climate!

Andy Yang
Andy Yang

as a student studying environmental science  at uc davis, i understand the probabilities behind climate research-- epa states global warming is "very likely" (~80% chance) caused by humans.. so i rarely comment on climate change even though i knew skeptics were clueless on how these numbers were derived.. but now i think people are more open and fair in judging these numbers.. sadly, only when the weather's gotten hotter