Since when has the sierra club had any say in,the matter anyhow? Last time I checked, the sierra club is in charge of jack-shit.
So if that cabal of useful idiot tree & bunny huggers want to shut down power plants, and are successful, SUE the living shit out of them for ths replacement technology and lost megawatt capacity.
Use their own tactics against them and their financial backers.
I was once a member of the SC. We specialized in taking inner city kids to back pack camping. I had to quit when I saw the left taking over the concept of wilderness. The SC could not even come out against unrestricted immigration, because it meant more votes (even though it also meant more growth and more power generation).
The power companies at one time planned their future power facilities based on expected growth of the population. Not since the SC has become the dominant force in the energy business. Now, if it gets too hot they have a device on your thermostat that turns the AC down until you are uncomfortable and in the winter when too cold you are invited to put on a sweater.
In a reasonable world, people would be free to spend their money on AC or heat if they wished. They would not be able to force their neighbors to use expensive and intermittent power, and if they were convinced that CO2 was “really” a problem, they would back nuclear and find a place to store nuclear waste. What is happening now is clearly a sham.