Whither Hurricane Activity?

摘要

A key question in the study of near-term climate change is whether there is a causal connection between warming tropical sea surface temperatures (SSTs) and Atlantic hurricane activity (1-3). Such a connection would imply that the marked increase in Atlantic hurricane activity since the early 1990s is a harbinger of larger changes to come and that part of that increase could be attributed to human actions (3). However, the increase could also be a result of the warming of the Atlantic relative to other ocean basins (4), which is not expected to continue in the long term (5). On current evidence, can we decide which interpretation is likely to be correct? To appreciate the problem, consider the observed relation between hurricane activity [power dissipation index (PDI)] (6) and SST in the main development region of Atlantic hurricanes (hereafter "absolute SST"). Between 1946 and 2007, this relation can be defined by a simple linear regression between the two quantities (see Supporting Online Material). This observed relation can be extrapolated into the 21st century using absolute SSTs calculated from global climate model projections (see the figure, top panel) (7). By 2100, the model projections' lower bound on 5-year averaged Atlantic hurricane activity is comparable to the PDI level of 2005, when four major hurricanes (sustained winds of over 100 knots) struck the continental United States, causing more than $100 billion in damage. The upper bound of the projected 5-year average exceeds 2005 levels by more than a factor of two. This is a sobering outlook that, combined with rising sea levels, would have dramatic implications for residents of regions impacted by Atlantic hurricanes.