Fact-Checking the Clean Energy and Climate Change Fact Sheet for Tennessee

The Southern Alliance for Clean Energy has a “fact sheet” asking, "How Will Climate Change Impact Tennessee?"

Of course, climate change has impacted Tennessee to such a degree that there has been absolutely no trend in its statewide average temperature since records began in 1895.

According to the fact sheet, "changing weather patterns also means increased drought events. Drought and heat waves have a particularly negative effect on Tennessee's dirty, high-risk energy generation resources."  Instead, what we find are statistically significant trends toward fewer droughts – not more – in the state over the past 120 years, which is consistent with the "fact" that there is a statistically significant trend towards more annual precipitation since 1895.  The long-term correlation toward less drought is also evident in each of the state's climate divisions.

The alarmism continues:

The May 2010 deluge that flooded much of Middle and West Tennessee is one of the more recent examples of the dangers posed by increasingly common weather events across the Southeast. We will face an increase of extreme weather events, including severe storms, heat waves, and crop-killing cold snaps, in a world impacted by climate change. These events take a large toll in terms of physical damage, lost economic productivity, higher insurance costs, and public health disasters.

Increasing heat waves?  Since the 1800s, the average summertime maximum temperature in the state has decreased.  There have been no significant trends in the number of days above 95º F across the state each year since records began in the first half of the 20th century, nor since 1970 or over the last three decades.

As for the statement that "the May 2010 deluge that flooded much of Middle and West Tennessee is one of the more recent examples of the dangers posed by increasingly common weather events across the Southeast," when one looks at the historical records, there are no significant trends toward greater maximum one-day rainfalls in this region since records began in the 1870s, nor since 1970 or over the last three decades.  The state government also probably oversold the concerns:

On May 1-2, 2010, the combined effects of a stalled frontal boundary and warm, moist air rising from the Gulf of Mexico caused West and Middle Tennessee to be inundated with record-breaking amounts of rainfall ... The entire region experienced '1000-year floods' caused by the fact that many locations received 10-20 inches of rain over a 48-hour period. The Cumberland River flooded both Clarksville and Nashville. On May 3 in Nashville the river, with a flood stage of 40 ft., crested at 51.86 ft., a level not seen since 1937. The next day in Clarksville, where the flood stage is 46 ft., the Cumberland crested at 62.58 ft. Other rivers flooded as well: the Duck River at Centerville and Hurricane Mills, the Buffalo River at Lobelville, the Harpeth River at Kingston Springs and Bellevue, and the Red River at Port Royal.

Thousand-year floods were observed? The flood peak for the Cumberland River at Nashville was well below the flood peak from 1927, as evidenced by the USGS annual peak streamflow data for this hydrometric station, and equal to the 1937 peak.

There is no evidence of climate change causing higher flood peaks in the Cumberland River, and absolutely no evidence of upward trends in peak flows at any of the other hydrometric stations mentioned in the state government article.  In fact, one could perhaps argue that peak flows are declining over time at these sites.

What about this claim?

Farmers are losing crops to drought and unreliable winter weather, expected to become more frequent in a warmer world. For example the entire state of Tennessee was designated a disaster area twice in 2007 – once for the 'Easter freeze,' and once for the crippling drought.

According to the National Association of State Departments of Agriculture, "Tennessee's top agricultural commodities include cattle and calves, soybeans, broilers, horticultural products, corn, cotton, dairy products, tobacco, hay, tomatoes, eggs, wheat, snap beans, grain sorghum, apples, peaches, farm chickens, squash, goats and sheep."

Here are the yields of soybeans, corn, cotton, and wheat for the state going back to when records began.  While the poor year of 2007 is evident, there is no trend to lower yields or more frequent years with bad yields.  The opposite is true.  Yields of all major crops in Tennessee are increasing, and have rebounded after 2007 to continue their upward trend.

There are no declining trends for other major crops such as tobacco, hay, tomatoes, sorghum, apples, or peaches, either, and certainly no sign of an impending climate change-induced farming catastrophe.  Overall, agriculture in Tennessee looks to be on solid ground.

This optimism and lack of imminent doom may be inconvenient for the clean energy groups, but it is reality.