Sea rise scenarios barely possible, says climate scientist Judith Curry

A catastrophic rise in sea levels is unlikely this century, according to a report by US climate scientist Judith Curry.

US climate scientist Judith Curry.

A catastrophic rise in sea levels is unlikely this century, with ­recent experience falling within the range of natural variability over the past several thousand years, according to a report on peer-­reviewed studies by US climate scientist Judith Curry.

Writing in The Australian today, Dr Curry says predictions of a 21st-century sea level rise of more than 60cm are increasingly difficult to justify, even if the predicted amount of global warming is correct.

“Predictions of higher than 1.6m require a cascade of ­extremely unlikely to impossible events using overly simplistic models of poorly understood processes,” Dr Curry says.

The review coincides with ­debate about whether some warnings about climate change relied too heavily on worst-case scenarios.

Dr Curry, a professor emeritus form Georgia Institute of Technology, said extreme, barely possible values of sea level rise were driving policies and local ­adaptation plans. She said an ­additional sea level rise of 60cm or less over a century could be a relatively minor problem if it was managed appropriately.

She said there was not yet any convincing evidence of a human fingerprint on global sea level rise because of the large changes driven by natural variability. “An increase in the rate of global sea level rise since 1995 is being caused by ice loss from Greenland,” she said. “Greenland ice loss was larger during the 1930s, which was also associated with the warm phase of the Atlantic Ocean circulation pattern.”

Dr Curry said predictions of sea level rise depended on climate models to predict the correct amount of warming.

Based on current greenhouse gas emissions, temperature rises to 2100 have been predicted by the Intergovernmental Panel on Climate Change reports to be 3C.

However, there were reasons to think the climate models were predicting too much warming. She said observed warming for the past two decades was smaller than the average warming predicted by climate models.

When compared with observations over the past 150 years, climate models produced too much warming in response to increasing atmospheric carbon ­dioxide, she said.

The latest IPCC report on 1.5C warming said there was a medium confidence that sea level rise would be about 10cm less by the end of the 21st century in a 1.5C compared to a 2C warmer world. Projections for a 1.5C and 2C global warming cover the ­ranges of 20cm to 80cm and 30cm to 100cm respectively.

There was high confidence in the IPCC report that sea level rise would continue well beyond 2100.

“Marine ice sheet instability in Antarctica and/or irreversible loss of the Greenland ice sheet could result in multi-metre rise in sea level over hundreds to thousands of years,” the IPCC report said. “These instabilities could be triggered at around 1.5C to 2C of global warming (medium confidence).”