A common argument made by climate change deniers is the fact that the antarctic ice shelf hit a record high earlier this year. But that argument doesn't hold water (so to speak).
Nobody is disputing that the antarctic ice shelf has posted record gains over the last couple of seasons, because it has. In fact, according to a recent report by NASA Goddard using datasets from the National Snow and Ice Data Center (NSIDC), the five-day average of Antarctic sea ice on September 19th of this year exceeded 20 million square kilometers for the first time since 1979.
However, these gains, which occur in one small quadrant of the Earth, don't constitute damning evidence against global warming. That's because, you see, our planet has more than one pole and the rate of ice loss in the Arctic is 300 per cent that of the rate of ice gain in the Antarctic. We're experiencing an overall (and accelerating) loss of ice at the global level regardless of what's happening along Western Antarctica.
"The planet as a whole is doing what was expected in terms of warming," Claire Parkinson, a senior scientist at NASA's Goddard Space Flight Center, said in a press statement. "Sea ice as a whole is decreasing as expected, but just like with global warming, not every location with sea ice will have a downward trend in ice extent." Just because someone dips your hand in cold water doesn't mean the rest of you isn't still on fire.
Since the late 1970s, the Arctic has lost an average of 20,800 square miles (53,900 square kilometers) of ice a year; the Antarctic has gained an average of 7,300 square miles (18,900 sq km). On Sept. 19 this year, for the first time ever since 1979, Antarctic sea ice extent exceeded 7.72 million square miles (20 million square kilometers), according to the National Snow and Ice Data Center. The ice extent stayed above this benchmark extent for several days. The average maximum extent between 1981 and 2010 was 7.23 million square miles (18.72 million square kilometers).
The single-day maximum extent this year was reached on Sept. 20, according to NSIDC data, when the sea ice covered 7.78 million square miles (20.14 million square kilometers). This year's five-day average maximum was reached on Sept. 22, when sea ice covered 7.76 million square miles (20.11 million square kilometers), according to NSIDC.
Only considering one side of the story (or globe) can confuse an already exceedingly complex global phenomenon. And that doesn't help anybody, whether you believe in global warming or not. [NASA]