A couple weeks ago, Seth Borenstein from the Associated Press published an astonishingly bad piece of climate science journalism on The Big Story board entitled “US hottest spots of warming: Northeast, Southwest.”
I debunked this AP story here soon after it was released. In short, the AP had claimed to use “the least squares regression method” to analyze National Climatic Data Center temperature trends in the lower 48 states, 192 cities, and 344 smaller regions within the states between 1984 and 2013. The AP then reported that “all but one of the lower 48 states have warmed since 1984” and that “92 percent of the more than 500 cities and smaller regions within states have warmed” since 1984.
As I noted in my previous article:
Here is what happened. The AP used ‘the least squares regression method’ to calculate the annual temperature trend for all these regions, but then proceeded to ignore entirely whether the regression method indicated if the trend was statistically significant (the typical criteria would be a p-value<0.05). This is first-year statistics level stuff. Quite simply, if your statistical test ('least squares regression method') tells you the trend isn't significant, you cannot claim there is a trend, since the null hypothesis (i.e., no trend) cannot be rejected with any reasonable degree of confidence. When I reanalyzed the data using the same approach the AP did – except I didn't ignore the statistical significance of the results, or lack thereof – I found that the AP should have reported that only 18 of the lower 48 states have statistically significant warming trends since 1984, and that only 31 percent of the cities and smaller regions within states have significant warming trends over this period, not the absurdly high 92 percent that the AP claimed.