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Vision Prize: scientists are worried the IPCC is underestimating sea level rise

Sea Level Rise: Graph by Stefan Rahmstorf

Graph by Stefan Rahmstorf comparing measured sea level rise (red and blue) to previous IPCC estimates (grey and dashed lines), showing sea level rise is happening faster than expected.


Powered by article titled “Vision Prize: scientists are worried the IPCC is underestimating sea level rise” was written by Dana Nuccitelli, for on Tuesday 18th February 2014 14.00 UTC

The Vision Prize is an online survey of scientists about climate risk. It’s an impartial and independent research platform for incentivized polling of experts on important scientific issues that are relevant to policymakers. Some of their previous survey results have found that about 90 percent of participating scientists believe that humans are the primary cause of global warming over the past 250 years.

In its latest survey, the Vision Prize asked participants questions about technologies to limit climate change, and about the latest IPCC report. Two of these questions asked about the likelihood that global average sea level will rise less than the IPCC lowest estimate (0.25 meters, or 10 inches), or more than the IPCC highest estimate (0.91 meters, or 3 feet) by 2100. These estimates are about 60 percent higher than in the 2007 IPCC report, which intentionally left out dynamic processes that cause effects like the calving of ice shelves into the ocean, because at the time they were not well understood. As expected, research has shown that the previous IPCC report underestimated the rate of sea level rise.

The Vision Prize results revealed that despite the much higher sea level rise estimates this time around, the survey participants are worried that the IPCC is still underestimating future sea level rise. 41 percent responded that it’s likely or very likely that sea level rise will exceed the IPCC highest estimate, and 71 percent answering that it’s at least as likely as not. Conversely, only 5 percent responded that it’s likely sea level rise will be less than the IPCC lowest estimate, and 83 percent called this scenario unlikely.

Global Average Sea Level Rise

These results broadly agree with a recent survey carried out by scientists in Germany and the US. In this survey, 90 researchers who’d published sea level research in the last 5 years concluded that sea level rise by 2100 is likely to be between 0.7 and 1.2 meters if we continue on a business-as-usual greenhouse gas emissions path. Two-thirds of the experts responded that sea level could rise more than the upper end of the IPCC’s projected range by 2100, consistent with the Vision Prize survey results.

On the other hand, if greenhouse gas emissions are reduced strongly, the experts expected sea level rise to be between 0.4 and 0.6 meters by 2100. These results suggest that the Vision Prize participants may be pessimistic that we’ll transition away from a business-as-usual emissions path.

Another Vision Prize question asked about the IPCC estimate of the planet’s sensitivity to the increased greenhouse effect. The latest IPCC report estimated that the planet will eventually warm between 1.5 and 4.5°C in response to the increased greenhouse effect if the amount of carbon dioxide in the atmosphere doubles. The 2007 IPCC report put the estimate at 2 to 4.5°C, but the three IPCC reports before that and the 1979 Charney Report had all estimated a 1.5 to 4.5°C climate sensitivity.

In the Wall Street Journal, climate contrarian Matt Ridley claimed that the change from the 2007 report to the latest version,

“…points to the very real possibility that, over the next several generations, the overall effect of climate change will be positive for humankind and the planet.”


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