2011 Atlantic Hurricane Season very active, but doesn't tell global story | Environment

With the end of the 2011 Atlantic hurricane season yesterday, it is time to review what actually happened.

Having noticed the increasing trend in extrapolating Atlantic basin tropical cyclone activity worldwide to suggest "climate change / global warming", my mentor and I embarked on a research project to analyze global tropical cyclone data, and let it speak for itself.

The 2011 forecast for the Atlantic told of an active year ahead regarding the number of storms that would form. This prediction verified, with 19 named tropical systems, seven of which became hurricanes. With 19 named systems, we were 73 percent above the average of 11 storms per year.

Our study covers the period from 1965 to 2010, with supplemental 2011 data. In looking at yearly numbers, we found that, on average, 69.5 named tropical systems form per year around the globe (Fig. 1).  For easier use in our graphs and charts, we rounded this number to 70.

In 2011, there were 61 named tropical systems worldwide, which is about 12 percent below the 45-year average. When NOAA issued their seasonal forecasts, they keyed on an ongoing La Nina event and forecast an above average season in the Atlantic, and a below average season in the Eastern Pacific. In 2011, Eastern Pacific tropical activity was 31 percent below average, with 11 named storms.

This long-term tropical cyclone record, during a period of increasing atmospheric carbon dioxide levels and warmer sea surface temperatures, has significant implications when it comes to discussing “climate change” (i.e., is the climate really changing?).

Recent information from the Intergovernmental Panel on Climate Change (IPCC, 2007) noted that, “…there is a less certain possibility of…a global decrease in total numbers of tropical cyclones.” It also keyed on, “… numbers of hurricanes in the North Atlantic have also been above normal in 9 of the last 11 years, culminating in the record-breaking 2005 season.”

Since accurate weather data for most global locations is limited to about 100 years or so, and satellite data is limited to only about 50 years, our study focused on short period weather averages, rather than longer-term climatic considerations.

What we found (see Fig. 2, Fig. 3, and Fig. 4) is that there are significant inter-basin relationships.  And, only one basin, the Atlantic, has shown a long-term upward frequency trend.  All other basins show stable to decreasing numbers of storms.

Due to data limitations, inconsistencies in basin-specific classification systems, and other factors, we have not yet examined frequency distributions of tropical storms and more intense hurricanes.  We have also not computed trends by basin and global statistics of Accumulated Cyclone Energy (ACE), a measure of overall storm energy.

However, this study does not support any global “climate” pattern shift. Rather, it shows that, globally, tropical cyclone frequency has remained mostly unchanged for almost the past 50 years.

For additional information on this study and other information about weather pattern linkages to climate change, please feel free to contact H. Michael Mogil.

***Disclaimer: Funding from external sources was not used in this independent research project and no such funding is planned for our ongoing research.***

***Research was conducted by Matt Bolton, meteorological intern, under the supervision of meteorologist H. Michael Mogil, CCM, CBM of How The Weatherworks.***