Nebulous Climate Claims in Louisiana

On Monday, Tulane University in New Orleans hosted the French Ameri-Can Climate Talks.  The Times-Picayune newspaper covered the event and published the following:

Without a significant reduction in greenhouse gases, including carbon dioxide produced by burning oil, gas and coal, sea levels could rise dramatically, threatening many coastal communities, [Donald Boesch, a New Orleans native who is president of the University of Maryland Center for Environmental Science] said. Changes in weather patterns caused by increased heat also will cause problems, including both drought and intense rainfall events in the same locations.

In south Louisiana, he said, these changes might produce severe drought-like conditions during the summer and fall, but at the same time, increased rainfall in northern and western parts of the Mississippi River's watershed could result in more frequent high river events.

'Climate change already has impacted water, plants, animals and people, especially those who rely on their local environments,' said Valerie Masson-Delmotte, a paleoclimatology expert with the French Climate and Environmental Sciences Laboratory.

She said temperature increases doubled between the 1960s and 1980s, and doubled again from the 1980s until today. If no cutbacks are made on greenhouse gases, she said, the future temperature increases 'bring us out of the range that our species has known.'

The climate record for southern Louisiana doesn't show any signs that climate change might produce more severe drought-like conditions – using the standard Palmer Drought Severity Index as an indicator – during the summer and fall.  Since records began in 1895, there has been absolutely no trend toward more drought-like conditions during the summer months in any of the state's three southern climate divisions.  And during the fall months, there is actually a statistically significant trend toward less drought over the past 120 years in the southwest Louisiana climate division, and non-significant correlations toward less drought in the other two southern climate divisions, during this time frame.

There are certainly no significant trends toward less summertime or autumn precipitation in southern Louisiana.  Quite the contrary.  There are, instead, significant trends toward more autumn precipitation in the southwest and south central climate divisions, and a near-significant trend toward more autumn rain in the southeast division.  Of course, there are also no significant trends in average summertime or autumn temperatures in southern Louisiana, either, since 1895.  As a result, the climate trends in the southern part of the state do not appear headed toward severe droughts.

This leads us to the state as a whole, where there has been no significant trend in the average temperature since records began.

The claim that “at the same time, increased rainfall in northern and western parts of the Mississippi River's watershed could result in more frequent high river events” also requires more information to fully assess.  The USGS hydrometric station on the Mississippi at Vicksburg shows a near-significant declining trend in annual peak flows since records began in 1858.  Similarly, peak flows at Baton Rouge don't appear to have any significant trends, either, since records began in 1828.

As is so often the case, the public is being provided with far too little information in the media to allow an informed opinion.  Rather, we get disjointed facts and vague claims that don't serve to properly educate those who are most interested in the issues.