"But the scientists understood that it was serious, and science journalists passed along their predictions of sea-level rise and other problems. (Later research confirmed the predictions. For example, a 2004 study estimated that a rise of 3°C sustained over centuries would suffice to melt the Greenland ice cap and put the world’s coastal cities deep under water.)"Gloomsday Predictions Have No Fault" was how Science magazine summarized the report of one authoritative review panel. The report was noticed even by the New York Times, although only deep on an inside page.(76)"
The above is from an excellent series of articles The Discovery of Global Warming by Spencer Weart. I came on it while hunting for a trustworthy resource on whether there is / should be an "upper limit" on the temperature effects of raising CO2 / Methane levels in earth atmosphere. No luck (literally) so far.
If one reads all the (huge) articles on the site, they will find authoritative answers to almost all issues discussed here on GW / GHG. That Greenland Icecap melt amounts to approx. 30 ft rise in sealevel. Granted, "Centuries", but it's a far cry from what many on these threads have said, eg. "Nobody's predicting entire icecap will melt".