Susan Kraemer informs us that, for a second time, 90 degree river shuts down a Tennessee nuclear power plant.

With the temperature in the Tennessee River approaching that of a nice warm hot tub, for a second summer in a row, three Tennessee Valley Authority nuclear power plants had to shut down this week.

Her conclusion about these events might terrify those still in denial: “we are beginning to experience the seemingly benign first years of catastrophic climate change.”

Because hot rivers are not good for fish, by law nuclear plants must not heat rivers above 86.9 degrees with their discharged water.

But that now quaint-seeming environmental protection was passed decades ago, well before global warming began to impact air and water temperatures. Summers like these make environmenal niceties like not overheating rivers with nuclear cooling water a bit irrelevant, because the river in question is already as hot as a hot tub.

“When the river’s ambient temperature reaches 90 degrees, we can’t add any heat to it,” TVA’s nuclear spokesman Ray Golden told the Times Free Press.

The shutdown marks the second summer in a row that TVA has had to shut down nuclear power as local rivers have reached record temperatures.

Last year’s shutdown cost the company $50 million in replacement power, a cost it passed along to its customers. To forestall the same problem reoccurring in future years, TVA invested $80 million in a seventh cooling tower at Browns Ferry, which began construction last October.

The additional tower would have been ready to prevent another summer heat shutdown by now, but construction has also been impacted by this year’s extreme weather.

“It was delayed because of the impact of the tornadoes, and some spring storms and some heavy rains,” said Golden. “It’s probably about 98 percent complete, and we hope it will be in service in the next one to two months.”

Together with last years losses, that’s another $140 million added to our cost of living in a warming world. According to Climate Science Watch, even by mid-June, the US had already suffered a total of $32 billion in economic damages due to global warming.