Hi All,

Below are some talking points that the Climate Nexus team pulled together regarding Hurricane Michael. Feel free to share and let me know if you have any questions. 

Cheers!

TROPICAL CYCLONES AND CLIMATE CHANGE

Science Talking Points

One of the clearest and most devastating impacts of climate change has been the dramatic amplification of damage done by hurricanes/tropical cyclones.

Sea level rise to date has elevated storm surge, increasing the reach of coastal flooding driven by hurricanes, especially along low-lying areas. As a result, the damages done by Superstorm Sandy extended another 27 square miles and added over $2 billion in damages.

Warming seas and a wetter atmosphere are supercharging the deluge delivered by tropical cyclones, increasing flood risk. Five different attribution studies documented the increase in rainfall dumped by Hurricane Harvey due to global warming. One study estimated that climate change increased Harvey’s rainfall by up to 38%.

Global warming is also directly driving tropical cyclone activity in some regions. The fingerprint of climate change has been documented in tropical cyclone activity in the Northwest Pacific (e.g. Japan and Philippines) and in the Central Pacific (e.g Hawaii). In the Atlantic, the U.S. National Climate Assessment reports that human factors have "contributed to the observed increase in hurricane activity since the 1970s.” While the balance of those factors is not known, at a minimum, global warming is increasing the potential speed limit for hurricanes, and we may be seeing that climate signal emerge in the Atlantic. This is what the future is projected to look like in a warming climate.

HURRICANE MICHAEL AND CLIMATE CHANGE

Science Talking Points

Increasing rainfall:

• Unusually warm seas and a warmer atmosphere are expected to help supercharge the rains delivered by Michael and amplify local flash flooding.

• The seas over which Michael traveled were up to 3.6°F (2°C) warmer than the historic average, a significant increase.

• The extremely heavy rainfall forecast along Hurricane Michael’s path is consistent with the UN IPCC Report published this week, which found the 1.5°C of warming human activity has increased overall extreme rainfall rates, and that we can expect more heavy rains from storms like this as warming continues.

• Unusually warm seas were identified as a major contributor to Harvey’s historic rainfall one year ago.  

Extending storm surge:

• Global warming is driving up sea levels, which allows storms along low-lying areas to push more seawater further inland.

• A study in the wake of Hurricane Florence found that sea level rise was responsible for 20% of the homes impacted by the storm.

• Sea level rise due to climate change extended the reach of Hurricane Sandy’s storm surge by 27 square miles, affecting 83,000 additional individuals and adding over $2 billion in storm damage.  

• Storm surge is often the most important impact of tropical cyclones in coastal regions. It accounted for 49 percent of storm-related fatalities between 1963 and 2012.

Increasing limit for wind speed:

• Global warming is heating up sea surface temperatures, which in turn raises the maximum potential energy (or potential speed limit) a storm can reach.

• Michael is fueled by unusually warm seas that have heated past the 83.3°F (28.5˚C) threshold for powering a major hurricane. Warming seas are a signal of climate change.