1 November 2012

What Those Who Understand Atmospheric Physics Are Talking About After Sandy

Posted by Dan Satterfield

Hat tip to Climate Central for making this graphic that explains why Sandy followed such a rare path. That Greenland High is what everyone who has taken a course in atmospheric physics is talking about.

Asking if Hurricane Sandy was caused by climate change is like asking someone at the South Pole which way is north. This kind of storm could almost certainly form in a world where the CO2 levels have been unchanging and Arctic sea ice levels were stable. That said, anyone who claims Sandy was ( or was not) caused by the changing climate just doesn’t get it.

If it seems like extreme storms are increasing over the Northeast USA, then you are right. The climate extremes index by the NOAA NCDC agrees.

It may be possible with some attribution and detection studies to say something about how much more likely it was for this storm to have occurred but that is for the future, and it will not be easy. So, what can we say about Sandy that is scientifically accurate??


1. The oceans are over a degree Celsius warmer than they were a century ago, and we saw record warm oceans (2-3 degrees C above normal!) off the East Coast for most of the last several months.

2. The planet itself is also a degree Celsius warmer than it was a century ago, and this means the atmosphere (on the whole) is holding 5-7% more water vapor than it was a century ago.

3. Sea level has risen at least a foot over the past century, but that is just on average. Along the coast of Delaware and Virginia, the sinking shorelines combined with the rising water, mean the water has risen over 18 inches in the past 60 years alone. Ask someone in New Jersey, who had a foot of water in their house, if they wish it were 18 inches lower.

What we CAN say is this:

If a storm exactly like Sandy hit in October of 1912, it would have been less wet  and the storm surge would have been a foot lower at least.. We can also say that a storm exactly like Sandy 90 years from now will be much wetter with water levels at least 24 inches higher. (The Mid-Atlantic coast is sinking at the rate of a foot a century, and the sea is rising at the same rate already. That’s two feet if nothing changes! The best science says the sea alone will rise 36 inches over the next century as the planet warms and the oceans expand.)

What meteorologists like myself, and climate researchers are talking about is the huge blocking high over Greenland.  October or November hurricanes re-curve into the Atlantic because of a much stronger fall jet stream, but the Greenland block turned Sandy into the coast. The track of Sandy was very RARE. Nearly unheard of actually, especially for this time of year. Dr. Jeff Masters has an excellent post about the Greenland block and how rare it is this time of year. Finish this post then read his.

Could the loss of Arctic sea ice be a factor in that big Greenland high pressure system. Dr. Jennifer Francis has research that says yes. (Andy Revkin at Dot Earth has a good post about this as well here.) Would the high have developed anyhow? Perhaps, but it would seem ridiculous to assume that the amazing loss of Arctic Ice would have little effect on the atmosphere over the Northern Hemisphere. That claim would be an extraordinary supposition that goes against the laws of physics and would require some profound evidence. The shoe is on the other foot now I think.

Rising sea levels and a warming planet are sneaking up on us little by little, but it will not be perceived that way. Instead, it will be realized in sudden and catastrophic events like floods, hurricanes and heat waves and droughts.

As I write this, 6.3 million people across 7 states are still in the dark…