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28 September 2005

Is there a link between the Arctic and hurricanes?

NSIDC scientists Mark Serreze and Ted Scambos answer some questions about the connection between the Arctic, sea ice, and hurricanes.

Is there a cause-and-effect link between the warming trend in the Arctic and the recent increase in Atlantic hurricane activity?

No. There is no evidence that Arctic warming invokes changes in conditions in the tropics that influence hurricanes. Similarly, there’s no obvious evidence that if we alter the frequency or intensity of hurricanes, the Arctic will respond.

Might Arctic warming and changes in hurricanes both be linked to the same underlying cause–global warming?

Maybe. One of our areas of expertise is Arctic change. The evidence is becoming strong that there is a growing greenhouse warming signal in this region. The recent sea ice losses may be an indicator of this effect, and warming appears to be the main underlying cause of changes in the Arctic sea ice and permafrost. But there are still skeptics; one of the big issues is that the Arctic is home to pronounced natural variations in climate.

Is global warming influencing hurricanes? This is presently a matter of vibrant and often polarized debate. Some prominent scientists are saying that the recent severe hurricanes are just part of a natural cycle. Others argue that global warming—which also warms the oceans—is playing a role. The basic argument is that the warmer the oceans get, the more likely it is that we’ll get hurricanes and that they’ll be intense.

But if more glaciers and polar ice melts, couldn’t that affect hurricanes?

Not in a direct sense. The real issue here is that if glaciers and ice sheets melt, this will contribute to a rise in sea level. So, low-lying areas like New Orleans will become more susceptible to flooding from storm surges associated with hurricanes.

A couple of other points should be kept in mind. First, increasing sea level is also related to ocean warming, because as the ocean warms, the water expands a bit. Second, sea ice is already floating in the ocean, so when it melts, it has little effect on sea level. (There is a tiny effect associated with salinity that we can pretty much ignore.)

Will the changes that we are seeing in the Arctic make the planet even warmer?

It’s likely that we will find this to be the case in coming decades, because of something called a positive feedback loop, in which an initial warming sets in motion a chain of events that causes further warming. The Arctic is very susceptible to this.

Sea ice is white, and therefore reflects a lot of the sun’s energy back into space, whereas dark, open ocean absorbs a lot more energy. As sea ice melts, it exposes more of the ocean. Similarly, over land, losses of snow cover expose more of the dark land surface. Because of this, the Earth’s overall albedo—its reflectivity—decreases.

So, a warming Arctic leads the planet to absorb more energy. That, in turn, could cause global average temperatures to rise still more.

Since 1979, satellite measurements have documented a general decline in the area of the ocean covered by sea ice. Especially large sea ice losses have been observed in the past four years. We may be just at the beginning of many changes in the coming decades.

More information:

All About Sea Ice
General information about Arctic sea ice formation, cycles, trends, affects on climate

State of the Cryosphere
Home page: An overview of the status of snow and ice as indicators of climate change
Sea ice
Specific information about how we measure sea ice

2005 Sea Ice Minimum Press Release
The latest scientific report on sea ice numbers for 2005

Union of Concerned Scientists
This organization’s take on the connection between hurricanes and global warming

Real Climate Change
Another view on the connection between hurricanes and global warming