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Why the IPCC Report Neglects the Benefits of Global Warming
It needs catastrophe scenarios.


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With the clock ticking toward December 2015 and the last chance to conclude a global treaty at the Paris climate conference, the job of the Intergovernmental Panel on Climate Change (IPCC) is to ratchet up the alarm. This it did in its report, released at the beginning of the week, on the impacts of climate change. It scored a bull’s-eye in the Financial Times: “Climate change harms food crops, says IPCC,” the headline ran. “Climate Signals, Growing Louder,” the New York Times opined, though the reality is that the volume is being turned up by the IPCC, not the climate itself. For the IPCC, this is mission accomplished — at considerable cost to the body’s residual credibility and integrity.

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The IPCC’s Working Group II, tasked with assessing the risks and impacts of climate change, could have chosen to make amends for its previous effort in 2007, which was widely panned for bias and numerous errors. Such was the outcry over the 2007 report that the Dutch parliament ordered the country’s Environmental Assessment Agency to carry out an audit. It found that the working group was dismissive of the potential benefits of climate change, and it criticized the group’s process for being insufficiently transparent. Similarly, a report by the InterAcademy Council, chaired by Princeton’s Harold Shapiro, noted that the group’s Summary for Policymakers had been criticized “for various errors and for emphasizing the negative impacts of climate change.” The summary contained many statements that “are not supported sufficiently in the literature, not put into perspective, or not expressed clearly,” the Council said.

The summary, as the object of intensive political editing by government officials, is a document designed to generate talking points for sympathetic politicians and pundits to re-spin. Scientific coherence is not its goal. Instead of raising the bar in pursuit of objectivity, the current working group doubled down on its 2007 summary: It unfurls a series of distortions designed to magnify the threats, ignore the benefits, and downplay the possibility of adapting to climate change.

Its most eye-catching claim is that negative impacts of climate change on crop yields are more common to date than positive impacts are. This improbable claim finds only the weakest support in the main body of the report, with its qualification that climate change played a “minor role.” It is, the report states, “extremely difficult” to define a clear baseline from which to assess the impact of climate change, and many non-climate factors are often difficult to quantify.

More egregiously, the summary speaks of rapid price increases following climate extremes since the 2007 report. This negligence amounts to downright dishonesty, as the summary omits mention of one of the principal causes of the 2007–08 spike in food prices, which is highlighted in the main body of the report. It was not climate change that increased food costs, but climate policies in the form of increased use of food crops in biofuel production, exacerbated by higher oil prices and government embargoes on food exports.

In attempting to attribute changes in farm output to climate change, the IPCC makes heavy use of models linking climate to agriculture, most of which assume that farmers don’t change their behavior as the climate changes. Instead of relying on speculative models based on the condescending assumption that farmers are robots and don’t adapt, a more intelligent approach would be to examine how farmers and agricultural output have reacted to climate change in the past. But the IPCC rendered this approach impossible when it erased previous periods during which temperatures might have been higher than they are now (symbolized by the Hockey Stick in the IPCC’s 2001 report). In 2005, Jonathan Overpeck, one of the drafting authors of the 2014 summary, e-mailed a colleague, saying he intended to “deal a mortal blow” to the supposed “misuse” of the Medieval Warm Period in the 2007 report. Overpeck succeeded in his aim of getting rid of the Medieval Warm Period.

A feature of the Working Group II is that it is dominated by by natural scientists, led by Chris Field, a biologist from Stanford. “It is true we couldn’t find very many benefits of climate change,” Field told the Financial Times. “We worked really, really hard to identify every benefit we could find.” But not that hard. As journalist Matt Ridley wrote in the Wall Street Journal in January 2013 on the greening of the planet, analysis of satellite data shows that between 1982 and 2011, 20.5 percent of the world’s vegetated area got greener, while just 3 percent grew browner; the most likely causes are higher temperature, higher levels of carbon dioxide, or both.

Of the 71 authors of the summary, only three are economists; of these, one did not engage in work on the summary for the last two years; and one, Richard Tol, insisted his name be removed from the summary because it is, as he put it, too alarmist and it makes silly claims. The IPCC’s own analysis suggests that a warming of 2 degrees Celsius could cause losses equivalent to 0.2–2 percent of world gross domestic product. Climate change is not, Tol says, humanity’s biggest problem. Nor is it even our biggest environmental problem.

In 1972, the British government appointed an environmental commission chaired by a botanist that produced a report entitled “Pollution: Nuisance or Nemesis?” The majority, comprising scientists, thought civilization was facing nemesis. The minority, led by the economist Wilfred Beckerman, opted for nuisance. Two years later, Beckerman wrote of his experience on the commission, observing that scientists “do not have a minimal understanding of the way that the world of human beings operates.” As the IPCC has shown this week, plus ça change.

— Rupert Darwall is the author of The Age of Global Warming: A History.



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