Sea level rise: Models and observations are starting to agree
Climate change models have typically underestimated the amount of sea level rise observed over the past century. The difference could point to a problem with the models, which attempt to account for effects such as the loss of glaciers and ice caps and the fact that a warming ocean takes up more space. Or it could simply be an artifact of sea level records from tide gauges (pictured), which are particularly spotty in the early part of the 20th century. Now it turns out that the gap between models and observations isn’t as big as scientists thought. A new analysis of tide gauge data has found that oceans rose just 1.2 millimeters a year between 1901 and 1990, researchers report online today in Nature. That’s less than the 1.5-millimeters-a-year rate calculated in 2011 and cited in the latest report of the Intergovernmental Panel on Climate Change (IPCC). It’s also much closer to the 0.5 millimeters per year calculated by IPCC climate models. The study, which relies on a sophisticated probabilistic technique that identifies patterns linking the sparse tide gauges, also found that from 1993 to 2010, sea levels rose 3 millimeters a year—in line with other tide gauge analyses. The jump from 20th century rates to 21st century ones supports what models have been saying all along: Sea level rise is accelerating at a frighteningly rapid rate.