Hurricane Sandy - The role of rising oceans

In the space of a week Hurricane Sandy, nicknamed 'Superstorm Sandy' and even 'Frankenstorm', hit the east coast of America and there was also the small matter of electing a new president. In the long-running election campaign, neither candidate had wanted to discuss climate change so it got pushed under the rug. Even with Sandy's presence, the issue of global warming was one which Obama, the Democrat, and Republican Romney spoke very little of in terms of anthropogenic impact.

Sandy certainly had a devastating effect on a number of countries including the US. The storm is thought to be responsible for the deaths of 132 Americans, to have caused £30-40 billion of damage, and to have left 6.2 million without power (BBC 2012). New York was one of the hardest hit areas thanks to a combination of population density, its location in the Hurricane's path, and the low lying nature of many parts of the city.

The twitter feed in the margin of this blog recently came to life with stories relating to sea level and the effect that this has had on storm events such as Hurricane Sandy. Before I move on further to talk about how Sandy could have influenced the election in my next post, I will first explore why climate change is being blamed.

You may be thinking hurricanes are a natural phenomenon and this is true. So what role have humans played in causing Hurricane Sandy? Well, the answer is that human-caused climate change amplified the hurricane's impact.

Figure 1: Yellow cabs line a flooded Queens, New York street as Hurricane Sandy passes 

Climate scientist Michael Mann has noted that over the past century, Battery Park, New York, has witnessed sea level rise of about a foot (Borenstein 2012). This has been attributed to a combination of land ice melt and thermal expansion in a ratio of approximately 6:4.

Hindsight is a wonderful thing. In a paper published in Nature in February earlier this year, Lin et al. (2012: 462) warned that:

‘The combined effects of storm climatology change and a 1 m sea level rise may cause the present New York City 100-year surge flooding to occur every 3–20 years and the present 500-year flooding to occur every 25–240 years by the end of the century.’

Thus, increased warming has led to sea level rise which will amplify a storm surge and cause even greater flooding! If more notice had been taken to this study by local authorities would the damage Sandy caused have been reduced?

In addition to rising sea levels a number of other factors played a role. Warming seas have the twinned effect of strengthening hurricanes and also increasing their likelihood (Emanuel 1987). Additionally, with a warmer atmosphere which can hold more water vapour, hurricane events such as Sandy are able to pull in more moisture, enlarging the size of the storm and the amount of rainfall, resulting in increased flooding (Trenberth 2012).

The path of Sandy has been analysed by several scientists, many of whom believe that the route would have been different were it not for a high pressure blocking ridge over Greenland which diverted the storm west (Masters 2012). As the ‘blocking high’ is rare for this time of the year it is thought that a record autumn Arctic ice melt is to blame.

Consequently it seems hard to argue that climate change is not shaping the world we live in today. While it was not to blame for Hurricane Sandy, several of its effects combined to contribute to the devastation that it caused in the US and the Caribbean.


References

BBC (2012) ‘Storm Sandy: eastern US gets back on its feet’ (WWW), London: BBC News (http://www.bbc.co.uk/news/world-us-canada-20150748; 17 November 2012).

Borenstein, S. (2012) ‘Scientists look at climate change, the superstorm’ (WWW), New York: Associated Press (http://bigstory.ap.org/article/scientists-look-climate-change-superstorm; 17 November 2012).

Emanuel, K. A. (1987) ‘The dependence of hurricane intensity on climate’, Nature, 326, 6112, 483-5.

Lin, N., K. Emanuel, M. Oppenheimer and E. Vanmarcke (2012) ‘Physically based assessment of hurricane surge threat under climate change’, Nature Climate Change, 2, 11, 462-7.

Masters, J. (2012) ‘Did climate change have a role in Hurricane Sandy’s unusual track into New Jersey?’ (WWW), ThinkProgress (http://thinkprogress.org/climate/2012/11/03/1125981/jeff-masters-why-did-hurricane-sandy-take-such-an-unusual-track-into-new-jersey; 18 November 2012).

Trenberth, K. (2012) ‘Opinion: super storm Sandy - what role did climate change play in this week’s massive hurricane?’ (WWW), New York: The Scientist (http://www.the-scientist.com/?articles.view/articleNo/33084/title/Opinion--Super-Storm-Sandy; 18 November 2012).