Hurricanes and Climate

Hurricane Florence has called attention to the uncertainties associated with hurricane prediction and with efforts to attribute some change in hurricane characteristics to climate change.

The primary event which focused this attention was the Washington Post editorial which accused President Trump of being “complicit”, presumably not in the occurrence of the hurricane, but rather in some model-estimated increase in the severity of the hurricane, because he has not taken actions to reduce climate change. This meme was picked up by many other media outlets and repeated frequently.

A study by the Climate Extremes Modeling Group at Stony Brook University “used a climate model (CAM5) to produce near real-time experimental forecasts of Hurricane Florence to assess how much human induced climate change has altered the anticipated rainfall, intensity and size of the storm. They concluded that the rainfall from the storm would be ~50% greater in the areas of intense precipitation, that the hurricane was ~80 km larger in diameter than it would otherwise have been and that the intensity of the storm would remain higher longer in its cycle as the result of human interference in the climate system.

The study did not mention that the speed of the hurricane was constrained by a blocking high pressure region to the North and West of the storm, which would result in higher precipitation totals due simply to longer residence time over the affected areas. The study did not also anticipate that the eye wall of the hurricane would breakdown and the intensity of the hurricane would decline from Category 4 to Category 1 on the Saffir-Simpson scale prior to landfall. The blocking high is a weather phenomenon apparently unrelated to climate change. The breakdown of the eye wall is not currently understood, but has not been attributed to climate change.

The self-appointed spokesperson for the consensed climate science community was quick to attribute the size, speed and intensity of Florence in part to climate change; and, to opine that there was more and worse to come if climate change were not effectively addressed.

The Washington Post attributed an increase in storm surge to the fact that sea levels have risen over the past century due to climate change. Their implication is that this increase is human induced, though sea levels have been rising at a relatively stable rate since the trough of the Little Ice Age.

Dr. Roy Spencer pointed out that Hurricane Florence was ”Nature’s Business as Usual, Not Climate Change”. He noted that there was no trend in major hurricanes making landfall in the US. He has also noted that while hurricane damage has increased over time, it is not as the result of an increase in hurricane intensity, but rather it is due to ill-advised increases in human building and development in coastal areas; and, that major US landfalling hurricanes have declined significantly since the1930s.

There has been little mention of the 12-year hiatus in major landfalling hurricanes prior to 2017, largely because it is not understood, but also because it does not support the narrative that human-induced climate change will worsen the frequency and intensity of hurricanes.