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Climate: Discussions raging on possible links between global warming and superstorm Sandy

Hurricane Sandy bearing down on the East Coast. Satellite image courtesy NOAA.

Record-breaking storm spurs more public awareness about the potential for more frequent extreme weather events

By Bob Berwyn

SUMMIT COUNTY — With several all-time weather records shattered and early estimates that Hurricane Sandy may cost the U.S. economy some $20 to $25 billion, it’s clear that the storm lived up to its billing. Along with the cleanup, there’s also a raging debate about whether global warming was a factor in the storm’s development and path.

On the one side, environmental activists seeking to limit heat-trapping greenhouse gases have jumped on the so-called super storm as an opportunity to tout their cause. On the other side, global warming deniers and others have pulled out timeworn statistics about past hurricanes that supposedly were equally as strong.

The arguments at the extreme sides of the spectrum don’t ring true. Of course, there is no way to scientifically prove that increases in air and ocean temps directly contributed to this storm. There’s still so much natural variability in nature that you just can’t establish a causal link.

But it’s also not true to say that there’s no link between climate and weather, as well-known über-deniers Anthony Watts like to claim. Weather is a function of the overall climate, and to say that climate and weather are unrelated shows the fundamental ignorance of the fringe global warming deniers.

The discussion has even reached the mainstream media, which is definitely a step forward for climate activists clamoring for more public awareness about links between global warming and extreme weather. U.S. News & World Report is running a poll that directly asks the question. As of late Tuesday, about 60 percent of respondents said they didn’t believe there is a link, but almost 40 percent said yes, which is a big deal in terms of public perception.

And here’s how the Associated Press reported on it in a lengthy science story that, remarkably, did not include a single link to any source documents or to the research by the scientists quoted in the story.

Here’s what we do know. Sandy hit the New Jersey shoreline with winds of 90 mph, a record storm surge and a barometric pressure of 946 mb, equalling the Great Long Island Express Hurricane of 1938 as the most powerful storm ever to hit the Northeast U.S. north of Cape Hatteras. It was the strongest hurricane to ever hit New York City and brought extreme weather to more than 100 million Americans, from Florida all the way to New England. Offshore buoys recorded waves as high as 40 feet.

We also know that Sandy set numerous records for barometric low pressure as she moved inland. We also know, according to NOAA, that both the overall frequency of Atlantic hurricanes, and the number of major hurricanes have increased since the 1970s, about the time greenhouse gases started becoming a major player in the atmosphere.

According to a NOAA fact sheet on climate and hurricanes, “Much of this recent increase in Atlantic hurricane activity began in 1995 as the tropical North Atlantic warmed and atmospheric conditions became conducive for increased hurricane activity, similar to the mid-20th Century.”

It’s not clear to anyone if that increase can be attributed to global warming or if it’s due to a combination of other cyclical climate factors, the World Meteorological Association concluded in a 2010 assessment.

The same organization found that, based on the best available science, greenhouse warming could actually decrease the total number of cyclones by up to a third, but that the average strength of those storms is likely to increase by 10 percent, and that near-storm rainfall rates could increase by 20 percent.

Other models suggest the number of storms could increase by as much as 60 percent, or decrease by that same amount. Clearly, scientists are all over the map on this question, but there is consensus that coastal areas will be more vulnerable to storm-surge flooding because of rising sea levels. Sea level in the New York area may be up to 12 inches higher than 100 years ago, but it’s not clear whether that’s all attributable to global warming. And sea surface temperatures in the Atlantic are, on average, about 2 degees warmer than 100 years ago.

In short, it’s purely circumstantial to say Sandy was caused by global warming, but it does fit a pattern of events suggesting storms with this scale of impacts may become more frequent.

“This is the kind of thing we’ve anticipated we’ll see a lot more of,” said Stephen Hamburg, a scientist with the Environmental Defense Fund. “We’ve seen 8 inches of sea level rise in last 75 years, and we’re going to see that accelerate. Then you add those storm surges, with infrastructure at or below sea level … The really big challenge is there’s natural variability associated with weather. That’s not going away, but with an event like this, we can say it’s consistent with we’re expecting to see.

“It’s beyond science to say that one storm is directly linked with rising CO2, but there’s strong science to show  it is happening with higher probability,” Hamburg continued. “We’ve got to plan accordingly, and try, at best, to mitigate the causes. We shouldn’t be having discussions about causality. We should be talking about adaptation and mitigation.”

 

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One Response

  1. (Copied from my post at another blog)

    Sandy’s left hook into New Jersey is an extremely unusually move for a hurricane, but it is consistent with some of unexpected effects from global warming.

    Global warming is more pronounced at the poles (especially the North Pole) than it is at the equator. The atmosphere’s normal west to east steering winds are produced by the temperature difference between polar and equatorial regions. When you reduce the temperature difference you reduce these winds. Once you reduce the wind flow, it becomes easier for high pressure areas to occasionally “get stuck”. The result is what is referred to as a “blocking high” (Alternately, a “blocking anticyclone”)

    I’ve posted a weather map at http://www.durangobill.com/Sandy500mb.jpg that shows the winds at the 500 mb level over North America a few hours before Sandy took the left hook into New Jersey. (Map was originally at http://weather.noaa.gov/fax/barotrop.shtml , and the 500 mb level is about half way up through the atmosphere as measured by pressure.)

    There is one low pressure area centered over western North Carolina, a second low pressure area to the southeast of New Jersey (which is hurricane Sandy), and a high pressure area off the east coast of Canada. In the northern hemisphere, winds blow counter clockwise around low pressure areas and clockwise around high pressure areas.

    The wind flow around the high pressure area east of Canada and the low pressure area over North Carolina generates a strong southeast to northwest wind field in between. Hurricane Sandy is right in the middle of this southeast to northwest wind field, and this is what caused the storm to hook to the northwest.

    The important part of the above is the blocking high pressure area to the east of Canada. If we had a normal west to east flow in the atmosphere, the high could have easily moved eastward, and the southeast to northwest wind flow (that picked up Sandy) would never have developed.

    The blocking high will break down over the next few days, but it will be a little late for the east coast. The bad news is that there will be more of these blocking highs over coming years. Where and when they develop will be random. Global warming deniers will continue to call them “weather”. Scientists will know that Global Warming is loading the dice for future “blocking high unusual events”.

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