08 October 2012

Antarctic sea ice and global warming

by Mark Robison, FactChecker, 6 October 2012

The claim
Record high amounts of Antarctic sea ice contradict global warming.

The background
Reno reader Judson Pierce contacted Fact Checker on Monday with a story from Newsmax headlined “Record Antarctica ice contradicts global warming trend”.
     He wanted to know whether it truly contradicts global warming and why the mainstream media seems to be ignoring this fact after widely reporting Arctic sea ice being at record lows.
    Pierce is right that, as of this writing, the mainstream media hasn’t reported much about the Antarctica ice. It’s likely they will, as the national data center for such statistics announced the news just this week with a story headlined “Arctic sea ice shatters previous low records; Antarctic sea ice edges to record high.”

    But the bigger question is one that seems to make sense: If Arctic sea ice at the north pole is at a record low and Antarctic sea ice at the south pole is at a record high, doesn’t this mean they are balancing each other out?
     To learn more, Fact Checker contacted Ted Scambos via email with help from the Climate Science Rapid Response Team. He has visited both polar regions several times, especially Antarctica. He is also lead scientist at the National Snow and Ice Data Center at the University of Colorado, where he works on Antarctic ice dynamics and polar climate change effects.
     Scambos said the trend for winter ice in Antarctica is to add about 5,000 miles each year whereas the Arctic summer loss is about 30,000 miles a year: “They certainly don’t offset each other.”
(Antarctica) has warmed by anywhere from 1 to 4 degrees Fahrenheit overall in the past 50 years,” he said. “This is based on weather stations, satellite data, climate models, and even the pattern of temperature left in the upper layers of the ice.
     But Antarctica is a cold cold place — the big difference between it and the north is that, in the north, a 4 degree warming can be the difference between skating and swimming. In Antarctica, it is the difference between one and two layers of long johns — beneath your parka and your fleece.
In other words, warming melts Arctic ice and it just keeps melting faster. But even with warming in Antarctica, it’s still cold enough that the ice doesn’t melt and can even increase.
Scambos said a big factor in increased Antarctic sea ice is the wind.
     The “westerlies” blowing around the continent have gotten stronger. This is because of the extreme cold but also because of the slowly warming ocean and land to the north, he said.
He said the wind shift is linked to both the ozone hole and greenhouse gases:
When ozone is not present, it does not absorb energy from the sun. So the atmosphere far above Antarctica is colder than it should be when the ozone is gone. This leads to a tendency to faster westerly winds.
The winds act to blow the ice around, and since melt is not much of a factor in Antarctic winters, there’s a trend toward more sea ice, with some exceptions.
    One exception is the warmest part of Antarctica, its peninsula that points up toward South America. Because temperatures are warmer there to begin with, global warming’s effects are more prominent, Scambos said, adding: “Sea ice has retreated regionally, the air has warmed at a very fast rate and 'permanent' ice shelves have retreated dramatically.”
     What about NASA’s James Hansen putting out a report predicting global warming would decrease Antarctic ice by 40 percent?
     Scambos said the new ice data is “a contradiction” to Hansen’s prediction, but he said Hansen’s assessment was done in the early 1980s. “We would not be doing our job very well if we had not learned something in 30 years,” he said.
    Aradhna Tripati — a climate scientist who has done research on polar climates for 11 years, has led teams of students at the Arctic and Antarctic, and is an assistant professor at the University of California, Los Angeles — said:
The observation of increased snowfall on Antarctica is entirely consistent with the global warming trend — and is what we’d predict using state-of-the-art climate models.
She added that advances in supercomputing have improved the ability to depict ice in models:
Climate models in the 1970s and early 1980s were incredibly simple in comparison to what scientists are using today... In fact, it has only been in the last decade or so that we’ve been able to do a decent job simulating sea ice in models.
Couldn’t these changes just be cyclical, the normal increases and decreases in ice that have happened for centuries? Scambos says:
     “In Antarctica, annual to decadal cycles might still push the overall trends in sea ice and climate back and forth. Long term, climate there will warm,” Scambos said.
     “In the Arctic, sea ice has not been as low as it is now in several thousand years (about 2000 BCE) — and so I ask, cycle of what? What other impact besides a warming trend — clearly expected considering what we’ve done to the atmosphere — could do this?”
     So, bottom line, what’s happening at the South Pole is consistent with global warming? “The conditions in Antarctica are, no question, a response to global climate change,” he said.

The verdict
This is not actually a new claim. In Michael Crichton’s 2004 thriller “State of Fear,” he used increasing Antarctic ice to dispute global warming. He gave a footnote to a study by Peter Doran to support his claim.
     Doran responded at the time, “Our results have been misused as ‘evidence’ against global warming by Michael Crichton.”
    The NewsMax story also misuses agreed-upon evidence that some Antarctic ice is increasing. Of course, the two sources NewsMax used to interpret this data —an anonymous blogger, a guy with an electrical engineering degree and zero climate scientists — would not pass muster for an eighth-grade science paper.
     To be clear, we’re talking about sea ice here, not land ice, which is decreasing at both poles and elsewhere. But an increase in Antarctic sea ice not only isn’t contradicted by trends toward higher global temperatures but is to be expected, according to the scientists who study it.

Truthmeter: 1 (out of 10)