Their letter, from the Pacific Institute, is nothing but propaganda, which is a just a continuation of all they have presented.
Hte actual rise in temp is much less than they claim. No one can consistently sense within 4 degrees F and that means other organisms are just as well adapted. Also, ~4 degrees F is 2K.
The average temp. of the Earth is 288K. The new total energy is 290K, if there's a 2K rise in T. That means there's only a 0.7% increase in the total energy of the system. According to the equipartition of energy principle, that means there'll only be a 0.7% increase in the average storm intensity, climate shift, or any other event.
Their claims are simply falsehoods and half truths presented as propaganda for the purpose of gaining control of political and economic decisions in general, and of the energy supply in particular.
As I understand it, global warming of the type pushed by warmists means significantly higher temperatures in the Arctic and very similar temperatures in the tropics.
The severity of the storms is driven primarily by the difference in temperature of these areas, not by the absolute temperature.
So global warming should in theory result in less severe storms.