John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
Satellites have picked up on vast gravitational shifts from melting Antarctic ice.
There are many dumb ways to deny climate change: noting the recent (and temporary) slowdown in heating, pointing to a snowy winter in your hometown, crying that it's part of the natural climate cycle. But it's pretty hard to look the other way on global warming when it's happening on such a massive scale that it's being felt in the earth's dang gravity field.
Satellites can image the planet in a slew of interesting ways, and one of these is gravitational. For instance, here's a 2011 model from the Gravity Field and Steady-State Ocean Circulation Explorer, which is operated by the European Space Agency. "The colours in the image represent deviations in height (–100 m to +100 m) from an ideal geoid," writes the ESA. "The blue shades represent low values and the reds/yellows represent high values":
European scientists recently were analyzing data from this satellite and another NASA one when they noticed a remarkable transformation around the South Pole. From 2009 to 2011, widescale dips in gravity appeared in western Antarctica. The researchers deduced that these deformations represented a huge loss of glacial ice, in some cases as much as 67 gigatonnes per year. That attrition is due in part to the fastest-known warming rates in the world.
Here are those places of altered gravity:
The space agency adds this historical context to Antarctica's melting woes:
ESA’s CryoSat satellite, which carries a radar altimeter, has recently shown that since 2009 the rate at which ice is been lost from the West Antarctic Ice Sheet every year has increased by a factor of three.
Ice change from CryoSat And, between 2011 and 2014, Antarctica as a whole has been shrinking in volume by 125 cubic kilometres a year.