Image:Hurricane Intensity Shift.png

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Description

History of recorded tropical storm tracks showing the major storm forming basins and land areas vulnerable to major storms.

This figure, which reproduces one of the key conclusions of Knutson & Tuleya (2004), shows a prediction for how hurricanes and other tropical cyclones may intensify as a result of global warming.

Specifically, Knutson & Tuleya performed an experiment using climate models to estimate the strength achieved by cyclones allowed to intensify over either a modern summer ocean or over an ocean warmed by carbon dioxide concentrations 220% higher than present day. A number of different climate models were considered as well as conditions over all the major cyclone forming ocean basins. Depending on site and model, the ocean warming involved ranged from 0.8 to 2.4 °C.

Results, which were found to be robust across different models, showed that storms intensified by a about one half category (on the Saffir-Simpson Hurricane Scale) as a result of the warmer oceans. This is accomplished with a ~6% increase in wind speed or equivalently a ~20% increase in energy (for a storm of fixed size). Most significantly these result suggest that global warming may lead to a gradually increase in the probability of highly destructive category 5 hurricanes.

This work does not provide any information about future frequency of tropical storms. Also, since it considers only the development of storms under nearly ideal conditions for promoting their formation, this work is primarily a prediction for how the maximum achievable storm intensity will change. Hence, this does not directly bare on the growth or development of storms under otherwise weak or marginal conditions for storm development (such as high upper level wind shear). However, it is plausible that warmer oceans will somewhat extend the regions and seasons under which hurricane may develop.

This work also suggests that the smaller changes in sea surface temperature occurring over the last century are unlikely to lead to detectable changes in the intensity of hurricanes. Despite this, some authors have reported apparent changes in the frequency and intensity of tropical storms (Webster et al. 2005, Emanuel 2005), though it is unclear if such changes can be attributed to global warming.

Copyright

This figure was prepared by Robert A. Rohde and closely follows a figure prepared by Knutson & Tuleya (2004). It is claimed that closely reproducing aspects of their figure for the purposes of discussing the conclusions of their work qualifies as fair use under United States copyright law. The unique elements of this image are released under the Global Warming Art license described below. Reusers of this image should consider whether their intended use would also meet the standards for fair use.

Aspects of this work are copyrighted and unlicensed. However, the individual who uploaded this work asserts that this use qualifies as fair use of the material under United States copyright law. Anyone wishing to make further use of this image should carefully consider fair use law and make an individual determination of whether their use is likely qualify for this protection.

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References

[abstract] [DOI] Kerry Emanuel (2005). "Increasing destructiveness of tropical cyclones over the past 30 years". Nature 436: 686-688.
[abstract] [full text] Knutson, Thomas R. and Robert E. Tuleya (2004). "Impact of CO₂-Induced Warming on Simulated Hurricane Intensity and Precipitation:Sensitivity to the Choice of Climate Model and Convective Parameterization". Journal of Climate 17 (18): 3477-3494.
[abstract] [DOI] Webster, P. J., G. J. Holland, J. A. Curry, and H.-R. Chang (2005). "Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment". Science 309 (5742): 1844-1846.