Expect more water to lap at your shores. That’s the take-home message from two studies out this week that look at the latest data on sea level rise due to climate change.
The first shows that current projections for the end of the century may seriously underestimate the rise in global sea levels. The other, on the ice sheets of Greenland and Antarctica, looks at just how much of the water stored up there has been moving into the oceans.
Both demonstrate that global warming is a real and imminent threat.
When we think of rising sea levels, we think of global climate change and melting ice caps. Yet there’s a disparity in the raw data. During the second half of the last century, global sea levels rose 1.8 millimeters per year, according to tide gauges. But it’s been determined that melting ice caps and glaciers have only contributed to 1.1 millimeters per year of that. So where did the other 0.7 millimeters come from? A new study has a remarkably simple answer: from you.
The extra rise in sea level not accounted for by melting ice caps can be explained by taking into account all the water we are pumping out of the ground and dumping into the ocean, says a team of researchers reporting in Nature Geoscience. Which actually makes a lot of sense.
Greenland’s ice sheet is more sensitive to global warming than previously thought and may already be approaching a critical threshold, researchers in Spain and Germany found.
The ice sheet may lose its ability to grow once warming reaches 1.6 degrees Celsius (2.9 degrees Fahrenheit) since pre- industrial times, according to a study published yesterday in Nature Climate Change. That’s below the previous best estimate of 3.1 degrees, the scientists at Madrid’s Complutense University and Germany’s Potsdam Institute for Climate Impact Research found.
“We might already be approaching the critical threshold,” Alexander Robinson, the paper’s lead author and an academic affiliated with both institutions, said in an e-mailed statement. “The more we exceed the threshold, the faster it melts.”
The United Nations estimates the Greenland ice sheet contains enough water to raise global sea levels by about seven meters (23 feet), threatening coastal cities from New York to London and Bangkok. Even so, the researchers said it could take thousands of years for the entire sheet to melt.
Temperatures have warmed 0.8 degree since industrialization began in the 18th century, an increase that marks the lower limit of the 0.8 degree to 3.2 degree range of uncertainty within which the melt threshold could be reached, according to the paper.
With 2 degrees of warming, it would take 50,000 years to melt the ice sheet, the scientists said. At 4 degrees, the time frame decreases to 8,000 years, and at 8 degrees, it’s 2,000 years.