Hurricanes and Climate Change

While there is a very strong case that increasing greenhouse gases have been the primary driver of global mean warming since 1900, it is difficult to detect a clear greenhouse gas-forced signal in Atlantic hurricane activity, apart from sea level rise, which will bring greater potential for coastal inundation by Atlantic hurricanes, even if the hurricanes themselves do not change.

Key long-term Atlantic hurricane activity indicators include the annual count of U.S. landfalling hurricanes or major hurricanes, which show no significant increase since 1900. In contrast, over the shorter period since 1980, many measures of Atlantic hurricane activity have increased. The Atlantic basin climate, including many hurricane and hurricane-related measures, is characterized by pronounced multidecadal variability, which makes it difficult to detect long-term (e.g., multidecadal to century-scale) past trends forced by increasing greenhouse gases. The observed multidecadal variability of Atlantic hurricane activity is generally believed to be a combination of response to changes in anthropogenic aerosols, dust, and volcanic forcing, along with a natural internal variability component. A greenhouse warming-related component may also be causing some long-term trends. The presence of these different potential contributing factors complicates the quantitative detection and attribution of changes in Atlantic hurricane activity to any one causal factor. However, this is an important unresolved science question because it has implications for how Atlantic hurricane activity may change over the next several decades.

We use model simulations to project how Atlantic hurricane activity may evolve over the 21^st century under different future emission scenarios. If internal climate variability has been an important player in past Atlantic hurricane multidecadal variations, it can be expected to continue to occur alongside the projected greenhouse gas-driven changes. An assessment of multiple studies suggests that hurricane-related precipitation rates will increase with greenhouse gas-driven warming (about 7% per deg C sea surface temperature increase), and that a 2 deg C global warming scenario will lead to about 3% increase of wind intensities of Atlantic hurricanes, but possibly a decrease in their overall number.