Hansen: Huge sea level rises are coming

I find it almost inconceivable that “business as usual” climate change will not result in a rise in sea level measured in metres within a century. Am I the only scientist who thinks so?

Last year I testified in a case brought by car manufacturers to challenge California’s new laws on vehicle emissions. Under questioning from the lawyer, I conceded that I was not a glaciologist. The lawyer then asked me to identify glaciologists who agreed publicly with my assertion that sea level is likely to rise more than a metre this century if greenhouse gas emissions continue to grow: “Name one!”

I could not, at that moment. I was dismayed, because in conversations and email exchanges with relevant scientists I sensed a deep concern about the stability of ice sheets in the face of “business as usual” global warming scenarios, which assume that emissions of greenhouse gases will continue to increase. Why might scientists be reticent to express concerns about something so important?
“Business-as-usual global warming will almost surely send the planet beyond a tipping point, guaranteeing a disastrous degree of sea level rise”

I suspect it is because of what I call the “John Mercer effect”. In 1978, when global warming was beginning to get attention from government agencies, Mercer suggested that global warming could lead to disastrous disintegration of the West Antarctic ice sheet. Although it was not obvious who was right on the science, I noticed that researchers who suggested that his paper was alarmist were regarded as more authoritative.

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