A new scientific report from the U.S. Climate Change Science Program has sharply reduced earlier estimates of global ice loss. The CCSP, which coordinates the efforts of 13 different federal climate agencies, has released updated figures estimating combined ice loss from Antarctica and Greenland at 48 cubic miles per year, a figure the Washington Post dolefully reports as "accelerated" ice loss.
But is it?
In 2006, a widely-reported study estimated ice loss from Greenland alone to be over 57 cubic miles per year. Another the same year reported Antarctic ice loss of 36 cubic miles -- a combined annual total of over 93 cubic miles. The new estimate, however, is only about half as high. In most rational circles, this would be cause for celebration.
Not for the Washington Post, however. Ignoring earlier estimates, it casts the figure in a threatening light by noting it's twice the amount of ice locked in the Alps. It fails to mention, though, that those 48 cubic miles, when spread out over the planet's 139 million square miles of ocean, works out to a sea level rise of only 2.1 inches per century. For you metric types, that's about half a millimeter a year. Even factoring in an additional increase for thermal expansion, the value is far too small for concern.
Glossing over all this, the Washington Post instead reports a potential rise of four feet by the year 2100. The figure is based on the assumption of unforeseen positive feedback effects which might accelerate ice loss, despite the fact that no evidence exists that this is happening, and even the report's own authors considered such a scenario "unlikely".
When one considers sea level has been rising for the last 18,000 years, at an average of about 25 inches a century, one sees even less cause for alarm. The rate of increase has actually slowed in past 4,000 years; before this, it often rose by as much as several meters per century.
The Post article also fails to point out the report doesn't include data for 2008, a colder year in which sea ice increased sharply, and preliminary estimates indicate that land-based ice sheets may have as well.
Some positive notes in the report are that "no clear evidence" for global-warming induced hydrologic changes (drought or floods) are being seen in the US, and that catastrophic events such as a shutdown of sea ocean currents ("thermohaline circulatory shutdown" ) or dramatic releases of methane (the "clathrate gun" hypothesis) seem increasingly unlikely.
To be fair to the Washington Post, 48 cubic miles/year is indeed larger than some estimates from the 1990s. But those figures were arrived at before the launch of advanced systems such as NASA's GRACE satellite. It's unclear how much of the difference in estimates is due simply to today's more accurate monitoring.
The report also indicates that current IPCC modeling doesn't accurately capture lubrication effects that may increase ice thinning and loss. However, a model prediction is not the same thing as actual measurements and observations.
The new figures obviously don't prove whether or not CO2 is warming the planet. However, they do strongly indicate that sea level rise isn't something that we -- or even our great-grandchildren -- need to worry about.
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