Charts: Climate Change Indicators: Tropical Cyclone Activity

Figure 1. Number of Hurricanes in the North Atlantic, 1878–2015

This graph shows the number of hurricanes that formed in the North Atlantic Ocean each year from 1878 to 2015, along with the number that made landfall in the United States. The orange curve shows how the total count in the green curve can be adjusted to attempt to account for the lack of aircraft and satellite observations in early years. All three curves have been smoothed using a five-year average, plotted at the middle year. The most recent average (2011–2015) is plotted at 2013.

Data source: NOAA, 2016;  Vecchi and Knutson, 2011
Web update: August 2016

Figure 2. North Atlantic Tropical Cyclone Activity According to the Accumulated Cyclone Energy Index, 1950–2015

This figure shows total annual Accumulated Cyclone Energy (ACE) Index values, which account for cyclone strength, duration, and frequency, from 1950 through 2015. The National Oceanic and Atmospheric Administration has defined “near normal,” “above normal,” and “below normal” ranges based on the distribution of ACE Index values over the 30 years from 1981 to 2010.

Data source: NOAA, 2016

Web update: August 2016

Figure 3. North Atlantic Tropical Cyclone Activity According to the Power Dissipation Index, 1949–2015

This figure presents annual values of the Power Dissipation Index (PDI), which accounts for cyclone strength, duration, and frequency. Tropical North Atlantic sea surface temperature trends are provided for reference. Note that sea surface temperature is measured in different units, but the values have been plotted alongside the PDI to show how they compare. The lines have been smoothed using a five-year weighted average, plotted at the middle year. The most recent average (2011–2015) is plotted at 2013.

Data source: Emanuel, 2016
Web update: August 2016