Does the expanding Antarctic sea ice disprove global warming?



First, the Arctic sea ice reached a record low extent this summer since satellite monitoring began, falling to 1.32 million square miles according to the National Snow & Ice Data Center. The previous record low, set in 2007, was 1.61 million square miles.

According to the center, the recorded decrease is significant:


Graphically, the all-time low during the satellite era looks like this:


Environmentalists and some climate scientists, such as Cambridge ocean physicist Peter Wadhams, have cited this rapid melting of the Arctic sea ice as a global disaster, and warn that a full summer collapse of the Arctic sea ice will happen fairly soon.

This loss does seem significant and worrisome.


However, climate science skeptics have seized upon the relatively stable and slightly growing Antarctic sea ice as evidence that this whole climate change is a bunch of hokum.

James Taylor, noting that the Antarctic sea ice is close to having a record high year, wrote for Forbes, “Please, nobody tell the mainstream media or they might have to retract some stories and admit they are misrepresenting scientific data.”

And blogger Steven Goddard, suggest the NSIDC is actively downplaying this news, writing that “NSIDC’s dissonance about this is astonishing.”

Here, from the NSIDC, is the actual trend in Antarctic sea ice.

Antarctic sea ice anomaly shows slight growth. (NSIDC)

So does this disprove global warming? The skeptics are saying that the Antarctic sea ice is growing as the Arctic shrinks. But are the two comparable? Not really.

Compare the modest (0.6 percent per decade) growth in the Antarctic sea ice with a comparable graphic showing the reductions in Arctic sea ice:

Monthly Arctic sea ice anomalies. (NSIDC)

The Arctic has been losing ice at a rate of more than 10 percent per decade, and the rate appears to be accelerating.

So what we can say is that while the Arctic has been losing ice, Antarctica has been holding steady, and perhaps growing slightly. Instead of using this as a wedge in the climate change debate, would it not be more proper to ask: If the world is warming, why isn’t the Antarctic sea ice melting?


Scientists have thought a lot about this question.

Unlike the Arctic, Antarctica is surrounding by water, so its less responsive to changes in air temperatures. Its climate is more governed by wind and ocean currents. Paradoxically, the ozone hole also may play a role in keeping Antarctica cool, scientists say.


Only recently have scientists begun to understand why, in part due to research by Judith Curry among other. In a 2010 paper (see abstract) in Proceedings of the National Academy of Sciences, Curry said the answer is tied up in a combination of natural variability and global warming. (By the way, skeptics, before you dismiss Curry you’d do well to understand that she’s a harsh critic of the IPCC.)

Here’s a deeper explanation of what she found, based upon an interview I conducted with her:

So give me a non-sound bite answer.

Sea ice can melt from both above and below, either heating from the ocean below or the atmosphere above. In the case of the Arctic most of the melting is driven from the warmer atmosphere above. In the Antarctic most of the melting has been driven from the ocean below. What our study has identified is that there’s been increased precipitation over the last few decades that has freshened the upper ocean, which makes it more stable so the heat below doesn’t make it up to the sea ice to melt it.

Freshens the upper ocean?

It decreases the saltiness. When you have a fresh layer on top that’s less dense it acts as a barrier to prevent the mixing of warmer water from below. It insulates the ice to some extent. We’ve also seen a big role of natural variability, over the past 30 years or so the dominant climate signal has been from the Antarctic Oscillation rather than from global warming. The net effect of all this has been an increase in precipitation, mostly snow. This diminishes the melting both from below and above. It stops the melting from above because snow has a higher albedo and reflects more sunlight.

At some point does this result in a net loss of ice rather than gains?

What happens in the 21st century projections is that the global warming signal begins to dominate. We still have the freshening of the upper ocean, but the upper ocean is getting warmer because of a warmer atmosphere. And the precipitation starts to fall more as rain than snow. Rain falling on ice speeds the melting from above.


Eric Berger