Hurricane Michael: The Science Behind Another Very Active Hurricane Season

Extreme weather continues to break its own records as the one-upper nobody wants around. Weather and climate-related damages caused an unprecedented $320 billion in damage in 2017, according to the United Nations research, and as of September 19, there had already been 30 percent more named storms than average in the western Pacific and the Atlantic, with Hurricane Michael joining the club this week. Arriving at the Florida panhandle on Wednesday, it was a Category 4 (130–156 mph), the most violent storm that’s ever hit the region.

Evidence is piling up, showing the connection between climate change and extreme weather, say scientists, despite that

“The most common misunderstanding is that we cannot attribute any role of climate change. We can,” Michael Mann, a professor of atmospheric science at Penn State tells Inverse in an email. “The fact is that we are seeing increasingly extreme floods, droughts, heat wave, wildfires, hurricanes and superstorms can be related to the warming of the planet and the impact that is having on weather systems.”

Research from the federal government’s Geophysical Dynamics Laboratory confirms Mann’s assessment. Warming will cause 21st century hurricanes to be higher in intensity, and rates of rainfall. Although hurricanes in the Atlantic are projected to decrease in frequency, their maximum intensity will increase by 5 percent.

Hurricane Michael easily claims its place in this trend as the third strongest hurricane to make landfall in the US with pressure of 919 millibars and windspeed of 155 mph, a mere two miles away from Category 5.

Researchers at the lab recently published their report on the 2017 hurricane season, noting that six major hurricanes classified last year’s season as “highly active,” an apt descriptor for anybody who witnessed the damage caused by Harvey, Irma, and Maria, which all made landfall last year.

Higher Intensity Increases Potential Damage

The complexity of hurricanes from varying times of formation or atmospheric temperature makes it difficult to pin down exact relationships between natural disasters and climate change for many years. But some consequences are clear. For example, rising sea levels, currently increasing 3.2 millimeters per year but accelerating, amplifies coastal flooding in the face of natural disasters, according to NASA. Waves may travel inland more easily, as the distance to travel between the surface of water and land closes.

Plus as global temperatures rise, the range of extreme temperatures expands. A warmer overall climate actually decreases the number of potential storms, but leaves more moisture in the air to form more intense storms, according to NASA. The increased gap in temperatures make droughts and floods more extreme as well.

Paired with the way humans tend to prepare for natural disasters, this makes lower frequency disasters at higher intensity potentially devastating. The Philippines is the unfortunate recipient of Category 5 typhoons on a regular basis, but as this level of intensity is a regular event, they’re prepared. But when Typhoon Haiyan’s peak wind at landfall in November 2013 was 190 mph instead of the 170 mph the region is accustomed to, 20 mph made the difference of more than 6,300 deaths.

What Can or Can’t Science Prove? The Emergence of Event-Attribution Studies

In the past few years, new research has reframed the connection between climate change and natural disasters in a subfield called extreme event attribution. Instead of asking whether an event was caused explicitly by climate change, researchers compare simulations with and without climate change to determine how climate change affects the risk of an event.

“I think it’s not so much that the philosophy has changed, but that the technology has changed,” Frederike Otto, professor at Oxford University told Scientific American. It’s a hot topic — from 2012-2015, the number of papers investigating event attribution jumped from 6 to 32, according to the National Academy of Science’s 2017 report.

Different events are also easier to analyze than others. Heat waves and droughts may be straightforward, but the complexity of hurricanes limit exactly how much scientists can figure out. But a few papers have breached a boundary where models suggest that events only could have happened if climate change conditions existed.