Here is a brief roundup
We used to believe that the polar ice caps would be gone sometime around 2080-2100 and that by that time the ocean's sea level rise would be about 1 meter at the most. We didn't really think that the earth was going to warm up more than 1-3 degrees Celsius before 2100 and that was IF global warming was actually happening due to greenhouse gasses (remember, we used to call it the "greenhouse effect").
Not too much to worry about, at least not for the next 75 years or so. . .
Then we began to see rapid warming and our understanding of aerosol particulates and their cooling effect on the upper atmosphere and how they had been masking the effect of global warming. We also began to understand that this masking effect was localized, specifically to the northern hemisphere where the emissions came from, and now that the amounts of sulfates in the air were being removed that the northern hemisphere was where the most rapid warming was occurring.
We then started to grasp the fact that even small changes in regional average temperatures could produce wild swings in temperature patterns, from later freezes to earlier thaws to periodic and unprecedented heat waves to super floods and 500-year droughts.
To increases in hurricane sizes and frequencies.
Over the next several years we began to refine our models to include the expansion of the Hadley Cell over the northern hemisphere and began to see that we would lose the Colorado river by around 2025 and that spring rainfall and summer monsoon rains in America's Midwest would decline by 40% (at minimum) by 2100.
And then we began to realize that the permafrost was melting much more quickly than we thought it would, that the polar amplification effect was happening at a rate over 50% faster than our models predicted, that the polar caps were going to be gone sometime around 2045, not 2080.
We began to see that sea level rise was the least of our concerns.
We saw that climate-induced pests (pine beetle) were increasing at an exponential rate and that their effects were beginning to create real economic impact as well as reduce the earth's ability to get rid of the CO2 already in the atmosphere. We began to see the collapse of northern hemisphere grain production due to prolonged heat waves that prevent germination of crops and droughts that stunt growth. And that the 40% decline in spring and summer midwest rainfalls was going to happen sometime around 2035 not 2100.
Then we found huge pockets of methane burping out of the arctic tundra, then from the shallow Eastern Siberian Arctic Shelf. We began to realize that the Arctic ice cap was going to be gone sometime around 2020. We realized that the reflectivity index of the polar cap was going to go from .95 (ice) to .65 (water) and that this would amount to a warming effect equal to 20 years of current CO2 production levels.
We started to see that, even though our models did not include an increase in methane emissions our models were off by 2.5 degrees Celsius and 50 years, so that, instead of 1 to 2 degrees Celsius average increases by 2050 we are starting to see what may be 3.5 to 4.5 degrees by 2050 and instead of 5-6 degrees by 2100 we are beginning to suspect it will become 7-8.5 degrees Celsius under business as usual scenarios.
We then began to realize that for every single degree Celsius rise increase of average temperature, the caloric production capability of the earth would decrease by, at least, 15%. (the 10% was based on calories from grain production rates but, if one factors in the grain feed of beef, pork and poultry calories this total goes up significantly).
We started to realize that the warming signals of the last 12 years were masked by China's sulfur dioxide emissions and now that China has begun aggressively reducing it's air pollution, the northern hemisphere temperatures have skyrocketed in the last 4 years.
And now we see that superstorms are threatening our population centers and mega-droughts and heatwaves are destroying our abilities to feed ourselves and that massive population areas are beginning to experience perpetual drought that will produce forced relocations of millions of people and that the boreal peatlands are going to emit more carbon in the next 10 years than humans have in the last 5. And that the boreal forests are going to (mostly) burn away in the next 10 years and that the ice caps will be completely gone by June 21, 2020.
And the AMOC (Atlantic Meridonal Overturning Circulation) current will be effectively halted by 2027, preventing the natural removal of 3% of current atmospheric CO2 each year. And the Arctic and Boreal Forests becoming net carbon emitters instead of capturing carbon (as they currently do).
Which now will prove to even the most optimistic realist that we are headed for 3.5 degrees Celsius warming by 2035, even in the best case scenario, and 8.5 degrees by 2100. Unless we decide to devote the entirety of our U.S. domestic economy to combat greenhouse gas production and prepare for the coming climate catastrophes.
And that sea level rise is the least of our worries right now.