By SETH BORENSTEIN
AP Science Writer

WASHINGTON (AP) — Have you heard that the world is now cooling instead of warming? You may have seen some news reports on the Internet or heard about it from a provocative new book. Only one problem: It’s not true, according to an analysis of the numbers done by several independent statisticians for The Associated Press.

The case that the Earth might be cooling partly stems from recent weather. Last year was cooler than previous years. It’s been a while since the super-hot years of 1998 and 2005. So is this a longer climate trend or just weather’s normal ups and downs?

In a blind test, the AP gave temperature data to four independent statisticians and asked them to look for trends, without telling them what the numbers represented. The experts found no true temperature declines over time.

“If you look at the data and sort of cherry-pick a micro-trend within a bigger trend, that technique is particularly suspect,” said John Grego, a professor of statistics at the University of South Carolina.

Yet the idea that things are cooling has been repeated in opinion columns, a BBC news story posted on the Drudge Report and in a new book by the authors of the best-seller “Freakonomics.” Last week, a poll by the Pew Research Center found that only 57 percent of Americans now believe there is strong scientific evidence for global warming, down from 77 percent in 2006.

Global warming skeptics base their claims on an unusually hot year in 1998. Since then, they say, temperatures have dropped – thus, a cooling trend. But it’s not that simple.

Since 1998, temperatures have dipped, soared, fallen again and are now rising once more. Records kept by the British meteorological office and satellite data used by climate skeptics still show 1998 as the hottest year. However, data from the National Oceanic and Atmospheric Administration and NASA show 2005 has topped 1998. Published peer-reviewed scientific research generally cites temperatures measured by ground sensors, which are from NOAA, NASA and the British, more than the satellite data.

The recent Internet chatter about cooling led NOAA’s climate data center to re-examine its temperature data. It found no cooling trend.

“The last 10 years are the warmest 10-year period of the modern record,” said NOAA climate monitoring chief Deke Arndt. “Even if you analyze the trend during that 10 years, the trend is actually positive, which means warming.”

The AP sent expert statisticians NOAA’s year-to-year ground temperature changes over 130 years and the 30 years of satellite-measured temperatures preferred by skeptics and gathered by scientists at the University of Alabama in Huntsville.

Statisticians who analyzed the data found a distinct decades-long upward trend in the numbers, but could not find a significant drop in the past 10 years in either data set. The ups and downs during the last decade repeat random variability in data as far back as 1880.

Saying there’s a downward trend since 1998 is not scientifically legitimate, said David Peterson, a retired Duke University statistics professor and one of those analyzing the numbers.

Identifying a downward trend is a case of “people coming at the data with preconceived notions,” said Peterson, author of the book “Why Did They Do That? An Introduction to Forensic Decision Analysis.”

One prominent skeptic said that to find the cooling trend, the 30 years of satellite temperatures must be used. The satellite data tends to be cooler than the ground data. And key is making sure 1998 is part of the trend, he added.

It’s what happens within the past 10 years or so, not the overall average, that counts, contends Don Easterbrook, a Western Washington University geology professor and global warming skeptic.

“I don’t argue with you that the 10-year average for the past 10 years is higher than the previous 10 years,” said Easterbrook, who has self-published some of his research. “We started the cooling trend after 1998. You’re going to get a different line depending on which year you choose.

“Should not the actual temperature be higher now than it was in 1998?” Easterbrook asked. “We can play the numbers games.”

That’s the problem, some of the statisticians said.

Grego produced three charts to show how choosing a starting date can alter perceptions. Using the skeptics’ satellite data beginning in 1998, there is a “mild downward trend,” he said. But doing that is “deceptive.”

The trend disappears if the analysis starts in 1997. And it trends upward if you begin in 1999, he said.

Apart from the conflicting data analyses is the eyebrow-raising new book title from Steven D. Levitt and Stephen J. Dubner, “Super Freakonomics: Global Cooling, Patriotic Prostitutes and Why Suicide Bombers Should Buy Life Insurance.”

A line in the book says: “Then there’s this little-discussed fact about global warming: While the drumbeat of doom has grown louder over the past several years, the average global temperature during that time has in fact decreased.”

That led to a sharp rebuke from the Union of Concerned Scientists, which said the book mischaracterizes climate science with “distorted statistics.”

Levitt, a University of Chicago economist, said he does not believe there is a cooling trend. He said the line was just an attempt to note the irony of a cool couple of years at a time of intense discussion of global warming. Levitt said he did not do any statistical analysis of temperatures, but “eyeballed” the numbers and noticed 2005 was hotter than the last couple of years. Levitt said the “cooling” reference in the book title refers more to ideas about trying to cool the Earth artificially.

Statisticians say that in sizing up climate change, it’s important to look at moving averages of about 10 years. They compare the average of 1999-2008 to the average of 2000-2009. In all data sets, 10-year moving averages have been higher in the last five years than in any previous years.

“To talk about global cooling at the end of the hottest decade the planet has experienced in many thousands of years is ridiculous,” said Ken Caldeira, a climate scientist at the Carnegie Institution at Stanford.

Ben Santer, a climate scientist at the Department of Energy’s Lawrence Livermore National Lab, called it “a concerted strategy to obfuscate and generate confusion in the minds of the public and policymakers” ahead of international climate talks in December in Copenhagen.

President Barack Obama weighed in on the topic Friday at MIT. He said some opponents “make cynical claims that contradict the overwhelming scientific evidence when it comes to climate change – claims whose only purpose is to defeat or delay the change that we know is necessary.”

Earlier this year, climate scientists in two peer-reviewed publications statistically analyzed recent years’ temperatures against claims of cooling and found them not valid.

Not all skeptical scientists make the flat-out cooling argument.

“It pretty much depends on when you start,” wrote John Christy, the Alabama atmospheric scientist who collects the satellite data that skeptics use. He said in an e-mail that looking back 31 years, temperatures have gone up nearly three-quarters of a degree Fahrenheit (four-tenths of a degree Celsius). The last dozen years have been flat, and temperatures over the last eight years have declined a bit, he wrote.

Oceans, which take longer to heat up and longer to cool, greatly influence short-term weather, causing temperatures to rise and fall temporarily on top of the overall steady warming trend, scientists say. The biggest example of that is El Nino.

El Nino, a temporary warming of part of the Pacific Ocean, usually spikes global temperatures, scientists say. The two recent warm years, both 1998 and 2005, were El Nino years. The flip side of El Nino is La Nina, which lowers temperatures. A La Nina bloomed last year and temperatures slipped a bit, but 2008 was still the ninth hottest in 130 years of NOAA records.

Of the 10 hottest years recorded by NOAA, eight have occurred since 2000, and after this year it will be nine because this year is on track to be the sixth-warmest on record.

The current El Nino is forecast to get stronger, probably pushing global temperatures even higher next year, scientists say. NASA climate scientist Gavin Schmidt predicts 2010 may break a record, so a cooling trend “will be never talked about again.”

An op-ed about (and hopefully debunking) the myth that global warming has plateaued.  From the Raleigh NC based News & Observer.  Thanks to KRT from the N&O for the great image above and to N&O op-ed editor Allen Torrey.

Warming is fact; denial is harmful

“The earth is cooling!”

Actually it isn’t, but we have all heard that so many times recently, we’re starting to wonder.

Globally, the last few years have indeed been cooler than 1998 and 2005. But this has no relevance for whether the planet’s climate is changing or whether people are the cause. The US civilian unemployment rate dipped this summer too, but would anybody credibly argue that was evidence that unemployment hadn’t risen during and as a result of this recession?

According to NASA, the hottest ten years since 1880 (when continuous instrument records begin) have occurred since 1996, and the planet’s temperature is still increasing. The only way to arrive at the conclusion that global warming has “plateaued” as George Will suggested last week in the N&O, is to begin your analysis in 1998; the warmest year on record.  In science, the technical term for choosing your data to make a point is “cherry picking”.

Like many climate change skeptics, Will is confusing weather with climate, which encompasses longer time periods; generally 30 years or more. The shorter-term fluctuations Will is fretting about are natural, have been happening for centuries, are well understood by climate scientists and are predicted by global climate models. It is the longer-term progressive warming that began over a century ago – and coincides with the buildup of greenhouse gases in the atmosphere – that is cause for concern.

Climate change skeptics like Will are successfully making the public think the evidence of our impact on the earth’s climate is confusing and contradictory. The details are complicated, but the basic science is actually simple. Have you ever climbed into a closed car on a sunny August afternoon?  Pretty hot wasn’t it?  That is essentially what the growing layer of gases in the atmosphere does to the earth, trapping in the heat caused by the sun warming up the land, just like it warms up the dashboard in your car.

Here in the world’s wealthiest nation the impacts of climate change on most of our lives have been relatively minor. Elsewhere, crops are failing, temperature sensitive diseases like malaria and cholera are increasing, and coastal villages are preparing to move to higher ground. In the US, arguing about whether the earth is warming is political sport. Elsewhere, the argument has moved on to which new technologies might reverse climate change, how societies can adapt to it, and who should pay for the costs.

Elsewhere, though, climate change is a bread and butter issue. When a coral reef in Papua New Guinea is wiped out by warming oceans, local fisheries collapse and fisherman can’t afford to send their kids to school. When Arctic permafrost melts, the physical underpinning of entire Alaskan villages is endangered. Nearly 1 billion people, or 1 in 7 worldwide, live at low coastal elevations and are experiencing flooding, erosion, and other direct impacts of climate change.

We haven’t experienced impacts of that scale here in North Carolina, but we eventually could. As sea level continues to rise, coastal communities here, too, will be threatened, and economies based on tourism and agriculture will suffer. Some of our fisheries could be affected too. One of the many affects of increasing the concentration of carbon dioxide in the atmosphere is that the oceans are becoming more acidic. This will affect economically important marine life like shrimp, crabs and oysters by making their skeletons more brittle and energetically costly to grow.

Given the clarity and relative certainty of the science and the scale of the potential social and economic impacts, why do newspapers publish articles denying climate change is happening? Social commentators like George Will certainly have freedom of speech and a general license to express their opinions on the editorial page. But would newspaper editors publish essays denying other major threats to humanity? Imagine an editorial arguing that cancer, poverty, HIV-AIDS or genocide don’t exist and are merely the product of a well-orchestrated scientific hoax.

In some countries, you actually do see such lies in the media. To Americans, this seems crazy, which is what the rest of the world thinks when they read denials about global warming in our newspapers. To everybody else, climate change is something they are already experiencing and are trying to find solutions to, rather than just another talking point in a never-ending culture war.

October 6, 2009

John Bruno, Carol Arnosti and Mark Sorensen

John Bruno, PhD, is an Associate Professor in the Department of Marine Sciences at The University of North Carolina at Chapel Hill

Carol Arnosti, PhD, is a Professor in the Department of Marine Sciences at The University of North Carolina at Chapel Hill

Mark Sorensen, PhD, is an Associate Professor in the Department of Anthropology at The University of North Carolina at Chapel Hill

Mark Sorenson and I just published an op-ed in response to George Will’s misguided essay denying global warming.  Not anthropogenic global warming, but simply global warming.  He argued on Oct 4 in the WaPost (and countless other papers around the country) that the warming has plateaued.  Sadly, he is wrong.

Will picked up on an equally incorrect story, by the usually on target Andrew Revkin who runs the DotEarth blog.

Revkin said “temperatures have been relatively stable for a decade”…The plateau in temperatures has been seized upon by skeptics as evidence that the threat of global warming is overblown. And some climate experts worry that it could hamper treaty negotiations and slow the progress of legislation to curb carbon dioxide emissions in the United States.” (link)

But there is no “plateau”.  The global temperature has continued to increase even during the last decade.

We have been blogging about (and attempting to correct) this for over a year (here, here, and here) as have many other bloggers and environmental writers including the NASA climate scientists who run the Real Climate web site (here). Their most recent article very succinctly debunks the “plateau” argument.  They include the graphic below, based on the NASA GISS dataset of global land and sea surface temperatures:

Global temperature according to NASA GISS data since 1980. The red line shows annual data, the larger red square a preliminary value for 2009, based on January-August. The green line shows the 25-year linear trend (0.19 ºC per decade). The blue lines show the two most recent ten-year trends (0.18 ºC per decade for 1998-2007, 0.19 ºC per decade for 1999-2008) and illustrate that these recent decadal trends are entirely consistent with the long-term trend and IPCC predictions. Even the highly “cherry-picked” 11-year period starting with the warm 1998 and ending with the cold 2008 still shows a warming trend of 0.11 ºC per decade (which may surprise some lay people who tend to connect the end points, rather than include all ten data points into a proper trend calculation). - from www.realclimate.org

Where’s the recent cooling or plateau you ask?  Nowhere in fact.

Below is a graphic of global temperature trends from five databases between 1999 and 2009.  They are all positive, i.e., no cooling, no plateau.  Note the hadcrut data (the green line)(the HadCRUT3v  data are developed in part by the Hadley Centre of the Met Office which is the UK’s National Weather Service and by the CRU ) displays the shallowest slope, yet the slope is still positive.

There is an incorrect meme in the blogosphere that this widely used dataset, unlike the NASA data (the rss  line in the graph below), does show a decline or at least a plateau.  But in fact it doesn’t:

It is well known that the Hadley data tend to run cool due to missing observations from the Arctic, one of the places on earth that have warmed the most (i.e., the Hadley HadCRUT3v  data tend to underestimate global warming – read the full explanation on RealClimate here).

The Met Office has posted a seemingly clear statement titled Climate change fact 2; temperatures continue to rise, in an attempt to make it clear that their data do not indicate warming has stopped.

Take another look at the Hadley data plotted below. The red line is the monthly temperature anomaly (deviations from a baseline) and the green line is the fitted curve beginning in 1999 (an intense El Nino year and the warmest year on record).  Note, again, there is no cooling or plateau.

The people coming to the conclusion that the earth is warming based on the Hadley data are not doing any type of trend analysis (or listening to the Hadley Centers interpretation).  They are instead simply drawing a line from the peak in 1999 to the dip in late 2008.  This is bogus for three reasons: (1) it is cherry-picking (picking the data to make a point, i.e., biased), (2) not a legitimate way to do a trend analysis (you can’t just ignore what happened in between the beginning and end points), and (3) it is totally irrelevant anyway!  It just doesn’t matter what happened last year or what happens next year.  The issue at hand is the effect of humans on climate not on day-to-day or year-to-year weather.  It is the long-term trend (see the graph below), that began over a hundred years ago, that we are concerned about.  (Can you see now why this whole issue – over the simple fact of whether the earth is even cooling – is driving scientists bonkers!)

Finally, as we point out in our op-ed; “According to NASA, the hottest ten years since 1880 (when continuous instrument records begin) have occurred since 1996, and the planet’s temperature is still increasing.”  You can see the current ranking (for what it’s worth) here.

To recap, we can see the data don’t show a plateau or a cooling trend and the British government even says their Hadley data don’t show a plateau or a cooling trend.

George Will’s WaPost colleague Ezra Kline has a great article explaining all this (again) to Will and millions of other AGW skeptics:

Will, whether he knows it or not, is relying on temperature measurements out of the U.K. Met’s office. Will thinks they show a “plateau” in global warming. Here’s what the Met says: “The rise in global surface temperature has averaged more than 0.15 °C per decade since the mid-1970s. Warming has been unprecedented in at least the last 50 years, and the 17 warmest years have all occurred in the last 20 years. This does not mean that next year will necessarily be warmer than last year, but the long-term trend is for rising temperatures.”

Brad Johnson, a climate blogger who does spend his days immersed in this stuff, writes that Will’s thesis is “pinned on an ambiguity of the English language. Just as the Yankees are a winning team but did not win their last game, global warming is terribly real even if 2008, one of the hottest years in recorded history, was cooler than 2007.” As Johnson explains, global warming is not shorthand for “every day will be hotter than the next everywhere on the planet.” It is shorthand for the observation that an “anthropogenic increase in greenhouse gases into the atmosphere is amplifying the natural radiative forcing of the troposphere’s temperature,” thus creating a general trend toward higher temperatures. The year-to-year variability that forms the basis of Will’s column is not a challenge to this theory. It is built into it.   [the Global Climate Models that have forecasted long-term warming over the next several centuries actually predict lots of year-to-year variability and even short-term declines, read about this here]

Is there a chance Will will issue a correction?  This is a matter of fact after all, not simply an opinion of political interpretation.  Will the WaPost Ombudsman suggest such a correction?  Or the editorial page editor?  This isn’t the first time Will has made demonstrably incorrect misstatements about global warming in his column  (see an account of his last run in with “facts”  here and a compilation of all the articles debunking his arguments here).  And in the past he and the WaPost editorial page editor haven’t been willing to make corrections or to even discuss the factual accuracy of his pieces rejecting that the earth is even warming.

Although I am more or less liberal and Will is a conservative (in the traditional, non-neo-conservative sense) I often find his arguments at least well-reasoned and sometimes insightful.  I even agree with him sometimes and he has more than once changed my mind.  But jeez, how can a guy who understands the Federal tax code and baseball get himself so confused about climate change?  I do not think he has ulterior motives or is in anyway corrupt.  I also don’t think he comes from this position out of ideology-he is usually, but not always, a skeptic, even of conservative ideology.  I suspect he is just getting bad information from the wrong places. Although, ironically, this time he was misled by the New York Times and moreover, by a highly respected enviro-journalist.

But I suspect Will has other sources.  As many have pointed out, the “the earth is cooling” and “global warming has plateaued” memes are taking over the blogosphere.  There are also passages in Will’s op-ed that are suspiciously similar to another recent op-ed by house member Joe Barton. Somebody is probably distributing briefings with talking points for climate change skeptics:

…to achieve the Waxman-Markey legislation’s 83 percent baseline reduction in carbon dioxide emissions by the year 2050, we will have to reduce the CO2 output in the United States to the level that we had back in 1910.  – Barton

The U.S. goal is an 80 percent reduction by 2050. But Steven Hayward of the American Enterprise Institute says that would require reducing greenhouse gas emissions to the 1910 level. – Will

The link to our op-ed in the Raleigh NC based News & Observer is here.  My co-author Dr. Mark Sorensen is a biological anthropologist at UNC.  We are co-teaching a class for non-majors on global change: From the Equator to the Poles: Case Studies in Global Environmental Change.  Dr. Carol Arnosti, a biogeochemist in my department assisted with the piece and is also an instructor in the class.

One question that keeps coming up in our class is why so few americans believe in Anthropogenic Global Warming (< 50% by some estimates).  The students have come up with a number of good explanations.  One is that the public – e.g., their parents – is so frequently misinformed, i.e., lied to, by widely respected authorities in the media such as Will. As Ezra Kline put it (link):

All this might be fine, if not for the credibility Will has by virtue of his column. But people who are reading Will’s column at their breakfast table and are not otherwise immersed in this debate might find Will’s thinking convincing, unaware that the points he’s raising have been continually and convincingly rebutted, and that his read of the evidence sharply differs from those of the scientists who are actually collecting and analyzing the evidence. That would be a shame.

We agree and essentially made the same point at the end of our op-ed:

Given the clarity and relative certainty of the science and the scale of the potential social and economic impacts, why do newspapers publish articles denying climate change is happening? Social commentators like George Will certainly have freedom of speech and a general license to express their opinions on the editorial page. But would newspaper editors publish essays denying other major threats to humanity? Imagine an editorial arguing that cancer, poverty, HIV-AIDS or genocide don’t exist and are merely the product of a well-orchestrated scientific hoax. In some countries, you actually do see such lies in the media. To Americans, this seems crazy, which is what the rest of the world thinks when they read denials about global warming in our newspapers. To everybody else, climate change is something they are already experiencing and are trying to find solutions to, rather than just another talking point in a never-ending culture war.