The above video, taken about three hours before high tide, shows how Sandy’s storm surge was already having a strong impact on Union City, New Jersey. The video serves as a nice counterpoint to evidence uncovered by Grinsted et al in a new study entitled Homogeneous record of Atlantic hurricane surge threat since 1923 showing that hurricanes and other severe ocean storms are growing more intense.
(Hat tip to Jeff Masters at Weather Underground for his excellent analysis of this emerging issue.)
Traditionally, wind speed has been used to gauge the force of storms. But since wind evidence has been less accurate until recent years, it has been difficult to provide a record of storm intensity over time. To avoid this problem, Grinsted turns to another, more reliable, measure — tidal gauges.
In his study, Grinsted used six tidal gauges at different locations along the US Gulf and East Coast to track storm surges from major events occurring from 1923 to the present. And what Grinsted found was evidence for increasingly powerful storms.
The above graph illustrates the number of major storm surges in any given year. Averages in 1923 steadily climbed from about 4 per year then, to nearly 7 per year now. This new, higher rate of powerful storm surges is also occurring in areas where ocean levels are 1 foot higher than they were during the 1920s and were development has encroached the shoreline boundary like never before. This combination of rising seas, increasingly powerful and more frequent storms, and runaway development has put a vast coastal region on a precipice. In coming years, this region will face at least a 1 meter rise in sea level, and, if the rate of increase illustrated in Grinsted’s study bears out, as many as ten major storm surge events per year on the East and Gulf Coasts by 2100.
(My personal opinion is that the 1 meter sea level rise predictions under business as usual fossil fuel emissions is a highly optimistic notion. More likely, unless emissions are reigned in, we will probably see at least 3 meters in sea level rise as first Greenland, then West Antarctic enter periods of rapid melt. In my view, the 1 meter range may be achieved only through rapid reductions in greenhouse gas emissions.)
We find that warm years in general were more active in all cyclone size ranges than cold years. The largest cyclones are most affected by warmer conditions and we detect a statistically significant trend in the frequency of large surge events (roughly corresponding to tropical storm size) since 1923. In particular, we estimate that Katrina-magnitude events have been twice as frequent in warm years compared with cold years.
In this statement, Grinsted establishes a direct link between storm intensity and human caused global warming. This statement also corresponds with a meteorological theory called heat engine theory, which shows that storms grow stronger as more heat energy becomes available.
Aslak Grinsted, John C. Moore, and Svetlana Jevrejeva (2012), Homogeneous record of Atlantic hurricane surge threat since 1923, PNAS, http://www.pnas.org/content/109/48/19601.