Is Climate Change Really Going to Give us a 20-Foot Sea Level Rise?

You may have seen claims in recent weeks that historic records show a global temperature rise could give us sea levels 20 feet higher than the norm. How accurate are these claims, and why is it important that we take this issue seriously?

The reports are a result of a University of Florida study that was recently published in the journal Science. The researchers, including lead author Andrea Dutton, wanted to investigate how historically Greenland and Antarctic ice sheets have reacted to global temperature rises and therefore get a glimpse of how current climate change might impact our sea levels.

The international team of scientists wanted to look at evidence of peak sea levels during several different periods of history and how that affected the polar ice sheets. They used computer models and geological evidence to specifically identify when average temperatures were around 1 to 3 °C (1.8 to 5.4 °F) above preindustrial levels–this being the standard level that we use to assess modern climate change. The researchers then looked at how high global sea levels were compared to the base rate when the ice sheets in Greenland and the Antarctic had retreated.

They discovered that, 125,000 years ago, sea levels rose between 20-30 feet when the average global temperature was one degrees Celsius higher than preindustrial levels. The researchers point out that this is about the temperature we’re currently at. A global target is to keep global temperatures below 2 °C, something that experts warn is critical in order to prevent the worst effects of climate change.

“This evidence leads us to conclude that the polar ice sheets are out of equilibrium with the present climate,” Dr. Andrea Dutton is quoted as saying. “As the planet warms, the poles warm even faster, raising important questions about how ice sheets in Greenland and Antarctica will respond. While this amount of sea-level rise will not happen overnight, it is sobering to realize how sensitive the polar ice sheets are to temperatures that we are on path to reach within decades.”

Climate science skeptics often cite the fact that estimates on things like temperature and sea level are not as reliable the further back in time we go, and therefore try to undermine warnings like this. Famously, they lambasted Al Gore for “exaggerating” sea level rise claims in his film An Inconvenient Truth. However, we know that sea levels are already rising, and now at the fastest rate recorded in the past century. Thanks to research like the above, which is not unique and sits among a good body of other research, we know that sea level rises of more than one meter are possible, and that they correlate with global temperature rise and retreating ice sheets.

The question of whether sea levels could rise as much as 20 feet may sound like scaremongering, but the data seems to support it as a very real possibility even if it is unlikely to be a problem during most of our lifetimes. The point is, if we want to guard against that happening, or even getting close to that figure, we need our governments to take sea level rise seriously.

Given that this area of research isn’t well explored, more investigation is necessary and the researchers say that they want to investigate which areas of the ice sheets might be most susceptible to change, as well as developing a greater understanding of exactly how polar ice sheet decline tallies against the rate of sea-level rise so we can get an idea of what to expect in the near to long-term future.