A look at weather extremes and the big-picture climate connections.

When Weather and Climate Gets Cloudy

On February 11, the Wall Street Journal posted an op-ed from London-based editorial writer Anne Jolis, about trends in severe weather. She described some preliminary results from the 20th Century Reanalysis Project that look back at indices of climate and weather variability over the past 130 years. The reanalysis project found no significant change to certain broad-scale weather patterns, a fact that Jolis used to contrast with what climate models have predicted for future trends in extreme weather. The words she choose to describe this — “researchers have yet to find evidence of more-extreme weather patterns over the period, contrary to what the models predict" — seem to be aimed at debunking what most climate model projections, and a growing body of detection and attribution studies, show: that climate change increases the odds of certain extreme weather events, and may intensify them as well. 

Jolis, unfortunately, confuses the readers by treating these issues too superficially.

The results from the 20th Century Reanalysis Project, which I also wrote about a few weeks ago, showed that the patterns of three specific climate variability indices hadn’t changed much over the past 130 years, but that doesn’t mean there aren’t any detectable trends in some types of extreme weather. There is more driving weather than just those three climate circulation measures, and many scientific studies have documented changing trends in extreme weather events. Furthermore, contrary to what a University of Colorado scientist is quoted as claiming, several studies, two of which were published just last week in the journal Nature, have linked these changing trends to increased greenhouse gases in our atmosphere. 

The other way in which Jolis confuses readers is by blurring the distinction between what the 20th Century project aims at, which is an improved understanding of past climate, and what the climate models have been projecting, which is future changes.

Today, three of the leading researchers involved with the 20th Century Reanalysis Project replied to Jolis via a letter published in the WSJ. They wrote to clear up the confusion that Jolis’s piece has very likely caused. In their words:

The article notes that the findings are "contrary to what models predict." But models project forward, while our analysis looked back at historical observations. We see no conflict between the 100-year-projection of changes in weather extremes resulting from additional carbon dioxide and the fact that our look back at three indicators showed no historical trend.

So, because of what Jolis’s piece may have wrongly suggested to the casual reader, it is important to recognize that the findings from the 20th Century Reanalysis Project do not contradict what the large body of research says about how increasing levels of carbon dioxide are expected to affect future weather extremes.

Jolis’s editorial was likely read widely. Within just a day or so, hundreds of comments appeared in response to it. It would be a shame if not as many people saw the scientists’ response, considering it’s the version of the story that represents the science straightforwardly, without distorting the facts. 

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