From the top, I want to include important context for the research results I am presenting. This research is based on peak warming of only either 1.5°C or 2°C. It is my educated opinion that such goals are unrealistic. Prevention of warming past 2°C is no longer a viable option based on the globe’s history of burning carbon-intensive fossil fuels as well as the medium- to long-term future, which doesn’t promise much of a difference. Furthermore, as I have stated numerous times in the past year, policy discussion would be better served if scientists would conduct research on developments that are much likelier to occur and not the world they want to see (i.e., higher vs. lower emissions scenarios). That said, this research fulfills an important role in the overall discussion because I think some of the results can be used as a “floor” – conditions are likely to reach higher magnitudes than those found in this and similar papers.
Michiel Schaeffer, William Hare, Stefan Rahmstorf & Martin Vermeer’s Nature paper was published on June 24, 2012. They examined sea-level rise in response to warming scenarios using a semi-empirical model. By 2100, global sea-level rise would be ~60cm above the 2000 level if global GHG emissions were zeroed by 2016. This is an obvious fantasy world, but it provides a useful benchmark for other scenarios the scientists examined. The reason sea-level rise would continue through the 21st century even if we haled emissions completely in the next 3-4 years is the response of the climate system to the anthropogenic forcing imparted on it through the 20th and early 21st centuries. If 1.5°C or 2°C warming is not exceeded, global sea-level rise would be 75-80cm above the 2000 level. The authors also report that unmitigated emissions could result in 100cm rise above 2000 levels. It is important to note that 20th century sea level rise has been estimated to be ~20cm. It doesn’t require much thought to realize that the rate of sea-level rise has increased throughout the 20th century and continues to do so in the 21st. Moreover, it is clear that since we will most likely warm beyond 2°C, the 75-100cm projection can be viewed as a reasonable estimate for a “floor”: actual sea-level rise could be greater than this.