SIEGEL: And is it wrong to draw any link between the warming temperature and the weather over the ocean?
HOERLING: So this is an interesting point. So the ocean temperatures adjacent to the Eastern Seaboard, this late to summer, have been running several degrees warmer than normal. Now, here’s a bit of a technical aspect. In terms of hurricanes formed over warm waters in the tropics, and they tend to begin decaying as they encounter cooler waters. The unusually warm waters off the Eastern Seaboard were however in areas where the background temperature is like 60 degrees Fahrenheit. So adding a few degrees Fahrenheit at that cool water temperature doesn’t matter too much for the intensity of a hurricane.
The commission quoted data from the National Oceanic and Atmospheric Administration that “the temperature of the surface waters from which Sandy drew energy were three to five degrees warmer than average”.
However, senior NOAA climate scientist Martin Hoerling said the higher sea-surface temperatures quoted by the Climate Commission were not significant in relation to Sandy.
Dr Hoerling told US public radio in the aftermath of Sandy that ocean temperatures adjacent to the US eastern seaboard had been running several degrees higher than normal.
But he said the unusually warm waters were in areas where the background temperature was relatively cool. “So adding a few degrees Fahrenheit at that cool water temperature doesn’t matter too much for the intensity of a hurricane,” Dr Hoerling said.
Dr Hoerling is a research meteorologist, specialising in climate dynamics, in NOAA’s Earth System Research Laboratory located in Boulder, Colorado.
He is chairman of the US CLIVAR (Climate Variability) research program, has served as editor of the American Meteorological Society’s Journal of Climate, and has published more than 50 scientific papers dealing with climate variability and change.
Late yesterday, Professor England conceded the sea-surface temperature highlighted in the Climate Commission document was not significant.
“The ocean temperature anomalies of 3-5C off New York that would feed energy into the extra-tropical cyclone in that part of the world matter much less than if such anomalies were located under the storm in the tropics,” Professor England said.
“Basically tropical cyclones are very sensitive to underlying ocean temperatures, but cyclones outside the tropics care somewhat less about the underlying ocean temperatures.
“So the climate change signal in Sandy is largely due to sea-level rise, the increased humidity in the world’s atmosphere, and the tropical ocean temperature anomalies. The temperatures up near New York, while still a factor in the storm, are less of a factor than the above three changes.”
Dr Hoerling said Sandy was not unprecedented. He said a storm surge at New York in 1821 was greater than that of Sandy. However, like the Climate Commission, he said rising sea levels could exacerbate the damage from big storms.
He said the record showed a rise in the total sea level of about 30cm over the past 150 years in New York. “We have a 14-foot (4.2m) rise related to Sandy,” he said. “So one foot out of 14 may not be something that is critical, but it may very well be in the sense that that last foot may be the foot that moved the water into very prone areas.”