The recent suffering and economic losses caused by Hurricane Katrina and the parade of storms that affected Florida in 2004 has energized a debate on what may be causing such “anomalous” hurricane activity. One of the culprits that has emerged in the arguments of some decision-makers, stakeholders, scientists, and citizens is global warming. An important debate is ongoing in climate and meteorological communities to determine whether anthropogenic forcing (e.g. global warming) is leading to an increase in hurricane frequency or intensity. Research in the literature continues to provide evidence on both sides of the issue.

One recent paper suggested that recent critics of the global warming-hurricane linkage failed to discuss the relationship between global warming and rainfall, sea level, and storm surge as related to tropical cyclones. Another recent study, however, notes that there is no documented correlation between global warming and the observed behavior of tropical cyclone-related rainfall, sea level, or storm surge. The Intergovernmental Panel on Climate Change (IPCC) has predicted an accelerated hydrologic cycle, reflected in increased precipitation. This acceleration can be linked to the nonlinear relationship between saturation vapor pressure and temperature. Few global studies exist that establish any significant trends in tropical storm rainfall related to natural or human-induced variability. One study found no trends in U.S. tropical storm and hurricane precipitation, but this study did not examine other global ocean basins. A recent assessment that there is no observational basis presently for claiming a linkage between greenhouse gases and TC-related rainfall is accurate.

One difficulty is that hurricanes are inherently ocean-based systems. When tropical cyclones are over ocean, rainfall is well correlated with storm intensity. Satellites provide a viable capability for monitoring tropical cyclone rainfall over oceans yet the availability of reliable and long-term datasets is limited. We use unique satellite-based precipitation estimates and ground-based rainfall totals to investigate trends in rainfall associated with tropical cyclone ocean basins and landfalling hurricanes in the United States. Over the past 30 years or so, we found statistically significant increases in accumulated rainfall in the North Atlantic, Western Pacific, and Indian Ocean basins during peak tropical cyclone seasons. Our analysis of 45 years of landfalling tropical storms and hurricanes in the contiguous United States also reveal that approximately 82% of storms with the largest maximum storm total rainfall occurred after 1980. This study is possibly the first study to observationally record significant trends in hurricane-related rainfall over the past 30-40 years.