I have not seen any explicit comment on this but it seems that there has been a large change over the years in what Warmists try to scare us with. There has been a Warmism 1 and a Warmism 2.
Warmism 1 is the Warmism of Al Gore, with sea level rises of 20 feet drowning most coastal cities. That was certainly scary and warranting of urgent action. But it was most implausible. 96% of the earth's glacial ice is in Antarctica and even at the continental margins the temperature there is many degrees below zero. So a few degrees of temperature rise might melt some sea ice but nothing more would happen. Melting sea ice cannot raise the sea level. So where was the required great volume of water going to come from? Mars?
Warmism 1 had another fault as well. It assumed a most implausible effect of clouds. It said that warming would be gradual until the cloud cover became much more extensive than it now is. And there is no doubt that a warmer world WOULD have more clouds as more water evaporated off the oceans.
But Warmism 1 at that point made two great theoretical leaps. They said that the increased cloud cover would warm the earth when clouds in fact normally cool the earth by blocking out the sun. But let's glide over that point and accept their assumption that clouds would warm us. The Warmist at that point makes another great leap. He says that at some point a "tipping point" would be reached so that warming would suddenly accelerate and we would really roast.
Normally, when scientists try to predict the future they make a straight line extrapolation from existing trends. But Warmism 1 aborts that. Because of the tipping point, the past is no longer a guide to the future. Things will get a lot hotter very suddenly. They will get much hotter than they would under a normal extrapolation from the past. So while scientific prediction of the future is possible in some instances -- by looking carefully at the past -- Warmism 1 abandons that and makes a prophecy based purely on speculation.
I have tried to tell the story of Warmism 1 as straight as I can but I think its implausibilities are nonetheless obviously gross. And, although it has never been formally abandoned by anyone, it has quietly faded away from most Warmist discourse. It is, for example, years since I have heard anything of the tipping point.
So Warmism 1 has been replaced by Warmism 2.
Warmism 2 is much less fantastical. It has reverted to the normal scientific method of predicting the future by extrapolations from the past. There is no Deus ex machina that causes warming to suddenly leap. It hypothesizes a steady process of warming at some specified rate. But finding that rate is the issue. Vast guesses about what CO2 does are used to get a rate.
Different authors assume different rates and the actuality always seems to be less than any predicted rate. So the accepted rate of warming has trended steadily down in the face of all the predictive failures. So under Warmism 2 we will have a temperature rise of only about 2 degrees Celsius and a consequent rise in sea levels of inches, not the yards predicted by Al Gore.
But that is rather boring. It is hard to frighten people with just a few inches of sea level rise so a whole new industry has arisen which says that the few degrees of predicted warming will lead to catastrophic weather events -- hurricanes etc. But even that is a dead end as dramatic weather events considered overall do not seem to be increasing and may even be decreasing.
So Warmism has in a way disappeared up its own back passage. It no longer has any pretence of science behind its warnings of doom. It is merely an example of telling a big enough lie often enough so that less informed people will believe it. And while it continues to give scientists a golden shower of research grant money, the myth will be maintained -- JR.'
Note added 3 April 2018. For useful background on the gestation of part of Warmism 2, see: http://quadrant.org.au/magazine/2018/04/climate-change-trial/