Are we cooling?

After a cool Arctic summer, sea ice at the North Pole has recovered somewhat from last year’s record low extent. While this is a welcome pause in the downward trend of sea ice extent, some are taking it a step further and hailing this rebound as evidence that the Arctic is no longer warming. But does the recent uptick mean that we have entered a period of global cooling? NSIDC scientists point out why we shouldn’t be reading too much into one summer of less sea ice decline.

A modest recovery

Data graph showing Arctic sea ice extent compared to the 1981-2010 average

This graph shows Arctic sea ice extent as of September 4, 2013, along with daily ice extent data for the previous five years. 2013 is shown in light blue, 2012 in green, 2011 in orange, 2010 in light purple, 2009 in dark blue, and 2008 in dark purple. The gray area around the average line shows the two standard deviation range of the data. Although sea ice extent has recovered somewhat this year, it is still below the 1981-2010 average. Photo credit: NSIDC

NSIDC scientists Julienne Stroeve and Ted Scambos indicated that a cooler summer prevented the dramatic ice melt seen in previous record years. Scambos added that the recovery could have been even more robust, saying, “The increase in sea ice extent in 2013 is in fact rather modest, considering the cool conditions that prevailed in the Arctic this summer.”

As well, the Arctic ice is still very thin. “The ice cover is still much thinner, even thinner than last year, and ice volume remains far lower than it was in the 1990s,” Scambos said. So despite the growth in extent, the overall condition and resilience of the year-to-year ice pack is still tenuous.

On top of meager ice conditions, some talk has focused on the percentage increase of sea ice this year over last year, which properly calculated, is close to 47 percent, according to Scambos. However, a large percentage increase in a small number may not amount to a meaningful increase; sea ice extent currently remains well below the 1981 to 2010 average. “Let’s not lose sight of the fact that the 2013 sea ice extent is low,” Scambos said. If you are low on gas, adding another gallon or two is a big increase, but the tank is still near empty. “The Arctic is just plain running low, and a single summer refill is not going to take us very far,” Scambos said. “2013 will still have lower ice extent than any year prior to 2007—to at least 1950.”

NSIDC scientists will issue their final analysis after this year’s melt season is complete, in early October on the Arctic Sea Ice News and Analysis site.

Variability or a trend?

Data image showing the decline in multiyear sea ice extent from 1980 through 2012

Multiyear ice, or ice that has made it through at least two summers, has diminished over the last three decades. The extent of multiyear ice, which includes all areas of the Arctic Ocean where multiyear ice covers at least 15 percent of the ocean surface, is diminishing by about 15 percent per decade. Photo credit: NASA/Goddard Space Flight Center Scientific Visualization Studio

Scambos also cautioned against relying on a single year to indicate a new trend of global cooling. There is simply not enough data. “We can’t use year-to-year variability to imply that the Earth is no longer warming,” Scambos said. “The decadal trend remains quite clear.” NSIDC scientist Mark Serreze also urges taking a longer view. He said, “The pattern over the last 100 years has been characterized by overall warming, with signals of natural climate variability.”

The underlying cause of sea ice decline—atmospheric warming caused by high levels of CO2 in the atmosphere—has not changed. Scientists expect some variability from year to year due to wind and weather patterns. This means it is well within the bounds of normal sea ice behavior to see some increase after last year’s record low.  “We may even recover for a few more years,” Serreze said. “However, the long term trend is downward, and will continue to be downward.”

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