Lately it seems like climate science is being portrayed by the media and politicians as a rapidly fracturing field — with a state of knowledge that is getting less and less certain with each passing day. Thus, it’s refreshing to be able to present a concrete and newsworthy example of how distorted that view really is.
A new study from some of the top researchers on the question of how climate change may affect hurricanes, several of whom have publicly sparred with each other in the past, published a study in Nature Geoscience this week that provides a consensus view of the state of scientific knowledge of how tropical cyclones may change in a warming world.
Their conclusions: Tropical cyclones are likely (greater than 66 percent confidence) to have stronger wind speeds and drop more rainfall due to climate change, and there is a 50 percent chance or greater that some ocean basins would see a large jump in the frequency of the most intense storms. However, the overall global number of tropical cyclones is likely to decrease or stay about the same as it is now.
Or to put it more simply, future storms are likely to be fewer in number, but stronger and wetter.
Tracks of simulated Atlantic Category 4 and 5 hurricanes for the present climate and for a warmer climate condition projected for the late 21st century. Source: Bender et al. 2010.
The study found that projections of globally averaged tropical cyclone intensity show increases of two to 11 percent by 2100. These numbers may vary significantly from region to region, though. For example, National Oceanic and Atmospheric Administration (NOAA) researchers using computer modeling recently found that the frequency of strongest hurricanes (Category 4 and 5 storms) could increase by 80 percent in the western Atlantic by 2100, even though the total number of tropical cyclones would decrease during the same period.
The new study refines the findings of the U.N. Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report of 2007, which put more weight on what, at the time, were new studies that showed the existence of detectable trends in storm intensity, particularly in the North Atlantic.
Given advances in scientific understanding and computer modeling since the IPCC report was prepared, the new study found that uncertainties in tropical cyclone observations are too large to conclude that there has already been a detectable increase in storm intensity, although they noted that several studies have found such trends in some areas.
“… considering available observational studies, and after accounting for potential errors arising from past changes in observing capabilities, it remains uncertain whether past changes in tropical cyclone frequency have exceeded the variability expected through natural causes,” the study states.
The conclusion that future storms are likely to be more intense has important implications for coastal residents, since the combination of increased coastal development, rising sea levels and stronger storms is likely to result in increased damages from future hurricanes.
“The future characteristics of intense tropical cyclones (Category 3-5) deserve particular attention, as these storms historically have accounted for an estimated 85 percent of US hurricane damage, despite representing only 24 percent of US land-falling tropical cyclones,” the researchers warn.
By providing a useful and newsworthy snapshot of where research on the hurricanes-climate change debate stands, the authors of the study have provided an example of how climate scientists can help communicate key findings to the public. Perhaps others in the climate research community can follow this example.
The authors of the study include Thomas Knutson of NOAA’s Geophysical Fluid Dynamics Laboratory, Kerry Emanuel of MIT, Chris Landsea of NOAA’s National Hurricane Center, Greg Holland of the National Center for Atmospheric research, and six other experts. Landsea and Emanuel, in particular, have had significant scientific disagreements in the past regarding the role of human activities in changing tropical cyclone behavior.
