Hurricane Harvey and Climate Change

by Jacob McCartney on 2017-09-06

Everyone has heard of Hurricane Harvey by now. Last month, a hurricane formed in the Gulf of Mexico as a category 4 hurricane and hit Texas as a tropical storm. Over the course of several days, the storm delivered 50 inches of rainfall in a short amount of time, and most of Houston, one of the largest cities in the United States, was devastated by several feet of flooding.

Tens of thousands of residents have been displaced. The death currently toll sits at 39. Several oil refineries have shut down, as I spoke of in a previous article, and a panicking population is creating temporary gas shortages in Texas, as well as surrounding states. People from all over Texas and the rest of the country have traveled to Houston to offer their help, and countless others have donated supplies or money.

In the wake of what is being labeled as one of the worst natural disasters in United States history, it is only natural to shift our gaze at the elephant in the room: climate change. Is climate change a key factor in this storm, and does that mean we should expect similar disasters at a higher rate in the near future?

I explored the subject of climate change in an earlier article, and I concluded that while it is part of a natural cycle, human activity is accelerating this change. This article is not an argument over whether or not Harvey was caused by man made climate change, but rather climate change in general. I will continue writing this under the assumption that the planet is indeed warming.

Connecting Harvey to climate change is difficult. There are a lot of factors in storms like hurricanes, and scientists appear to be overall be unsure if the two are connected.

NASA defines a hurricane or tropical cyclone as follows:

“Tropical cyclones are like giant engines that use warm, moist air as fuel. That is why they form only over warm ocean waters near the equator. The warm, moist air over the ocean rises upward from near the surface. Because this air moves up and away from the surface, there is less air left near the surface. Another way to say the same thing is that the warm air rises, causing an area of lower air pressure below.”

Hurricanes are fueled by warm air. An increase in temperature naturally would make a hurricane more extreme. Kevin Trenberth of the National Center for Atmospheric Research said that the Gulf of Mexico has been 2 degrees warmer than it usually is around this time of year. Since warmer temperatures can cause more extreme precipitation events, it is reasonable to say that Harvey was intensified by the warmer temperatures. Sir Brian Hoskins of the Grantham Institute for Climate Change also verified this, saying that “waters of the Gulf of Mexico are about 1.5 degrees warmer above what they were from 1980-2010.”

“There’s a well-established physical law, the Clausius-Clapeyron equation, that says that a hotter atmosphere holds more moisture,” BBC says. “For every extra degree Celsius in warming, the atmosphere can hold 7% more water. This tends to make rainfall events even more extreme when they occur.”

In 2014, the National Climate Assessment said that “[t]he heaviest rainfall events have become heavier and more frequent, and the amount of rain falling on the heaviest rain days has also increased.”

Even computer models report that we may see an increase in hurricanes due to climate change. The US Global Change Research Program Climate Science Special Report said this year that “both theory and numerical modeling simulations (in general) indicate an increase in tropical cyclone (TC) intensity in a warmer world.”

Nevertheless, there is evidence that Harvey had nothing to do with climate change. Kerry Emmanuel of MIT said, “It is awfully difficult to see climate change in historical data so far because hurricanes are fairly rare.” A study by NOAA in 2016 reported “no evidence” of changes in precipitation.

Harvey’s intensity could also be attributed to the fact that the system became trapped between two high pressure systems, one over the Atlantic Ocean and the other over the western US and Mexico. This kept is positioned over the Houston area, allowing it to unleash most of its damage in a single area. Had circumstances been different, could the storm’s damages have been dispersed over a larger area and been less catastrophic? Most likely.

Blaming the unusual strength of Hurricane Harvey on climate change is still uncertain. This is not the ideal answer for most people, but the complexity of tropical cyclones makes this difficult, so saying with certainty that climate change is to blame is not possible. However, with scientific models predicting an increase in tropical storms, and also with reports of Hurricane Irma, which is currently between Africa and North America, potentially breaking the scale and becoming a currently nonexistent category 6, the likelihood of increased storms seems to be the most likely. Only more time to collect data on these super storms will be able to tell us with certainty if climate change is responsible.


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