Statisticians reject global cooling
A terrific story by the AP’s Seth Borenstein, “Statisticians reject global cooling,” not only debunks that myth — it will make your head spin once again on error-riddled Superfreakonomics (coauthored by Levitt).
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 debunking will be no surprise to CP readers [see The BBC asks “What happened to global warming?” during the hottest decade in recorded history! and “NYT’s Revkin pushes global cooling myth (again!)], but the AP made three nice contributions. First, the AP talked to NOAA:
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.”
Second, “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”:
“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.
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.”
UPDATE: AP details here “How temperature data was analyzed.”
Third, the AP talked to Superfreakonomics coathor Levitt and top climatologist Caldeira, with an amusingly predictable outcome:
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.
Yeah, the book is filled with such errors “irony” — see Error-riddled Superfreakonomics, Part 3: It takes a village to debunk their anti-scientific nonsense.
So Levitt now says he doesn’t believe there is a cooling trend! Awesome, because Dubner is baffled that Caldeira ‘doesn’t believe geoengineering can work without cutting emissions.’ and Nathan Myhrvold jumpsed ship on Levitt and Dubner (on their blog!) asserting: “Geoengineering is proposed only as a last resort to try to reduce or cope with the even greater harms of global warming! … The point of the chapter in SuperFreakonomics is that geoengineering might be good insurance in case we don’t get global warming under control.” Did he even read the book?
Does anybody associated with the book stand behind any part of it anymore?
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&
rsquo;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.
Kudos to the AP for such a thoughtful and informative story.