Statisticians Cool Down the Climate Controversy

Why didn’t I think of this?  I know an estimated 90 percent of scientists agree that our earth is warming. I’ve heard the conservative claims of just the opposite: that the climate is cooling. (They point to what they see as a downward trend in temperatures over the last decade.) I’ve also seen the results of the latest Pew poll suggesting that only 57 percent of Americans believe in global warming—a drop of 14 percent since April.

I don’t need my math and statistics degrees to recognize that these numbers all add up to dangerous misinformation. But whenever I’ve tried to convince a skeptic that, yes, the climate really is warming—not cooling—the conversation usually dead-ends. Both of us invariably accuse the other of approaching the data with preconceived notions, cherry-picking our numbers.

The Associated Press’s ingenious solution: Give the dataset to some independent statisticians to analyze, but take out the temperature and year labels—thereby also eliminating any emotional prejudice.

In the blind stat test unveiled this week, four out of four statisticians chose global warming over climate cooling.

How could any previous analyses, regardless of their emotional backing, have found a cooling trend? It’s all about the data you choose, and how you slice it, explains the AP.  There are many opportunities for intentional or unintentional manipulation, including the choice between ground and satellite data (the former tend to be warmer; both were given to the statisticians), the range of years, and how those temperatures are averaged.

As the AP story explains, the preferred dataset for many skeptics begins in 1998—a scorching hot year—and includes only satellite-recorded temperatures over a 10-year period. In this relatively small dataset, the influence of that single year can be huge.  It can be enough to produce a statistically weak downward trend through the highly variable temperatures. But start the analysis in 1997 or 1999, and the 10-year trend tilts up.

A fairer assessment would be to analyze what are called 10-year “moving averages”.  In other words, average temperatures between 1997 and 2006, 1998 and 2007, and so on. Then look for trends in those averages. This way, any one anomaly has less sway. Such an analysis, according to the AP, shows temperatures over the last five years were higher than in any previous years.

Of course, even this is too narrow a view.  Climate trends over Earth’s history, beyond just 10 years ago, offer a far more telling tale. “To talk about global cooling at the end of the hottest decade the planet has experienced in many thousands of years is ridiculous,” Ken Caldeira, a climate scientist at the Carnegie Institution at Stanford, told the AP.

So why does the talk continue? As more and more scientific data pours in, all pointing to rising temperatures in the decades ahead, why are fewer and fewer Americans accepting it? What will change their minds?

Some suggest it will take more extreme events, or other health concerns that affect people personally.  In fact, a series of five research papers will be published in the November 27th issue of the journal The Lancet, nicely timed just a couple weeks before talks begin in Copenhagen. The studies will lay out various health effects of climate change—from increases in the number of heat waves and stagnant air masses to a potential rise in insect and water-borne diseases. The issue will highlight how reducing emissions could have a positive impact on public health.

I’m still (irrationally) hopeful something more “innocent” could do the trick. Maybe this new video on Huffington Post, for example, will capture the attention of some of the more visual skeptics: “Supermodels Strip for Climate Change.”

Of course, this may not necessarily motivate viewers to fight warming, but at least it might make them believers.