Is Hurricane Harvey a harbinger for Houston’s future?

Tropical cyclones also have many different characteristics that might change in unpredictable ways as they develop, including their track, their overall size, and their strength. Different aspects of the cyclones are likely to change in different ways, and no two cyclones are the same. Compare that with a heatwave, which often have similar spatial features.

For all these reasons, it is very hard to say exactly how climate change has affected Hurricane Harvey.

So what can we say?
While it’s hard to pin the blame for Hurricane Harvey directly on climate change, we can say this: human-caused climate change has enhanced some of the impacts of the storm.

Fortunately, in Harvey’s case, the storm surge hasn’t been too bad, unlike for Hurricanes Katrina and Sandy, for example. This is because Harvey did not travel as far, and weakened rapidly when it made landfall.

We know that storm surges due to tropical cyclones have been enhanced by climate change. This is because the background sea level has increased, making it more likely that storm surges will inundate larger unprotected coastal regions.

Building levees and sea walls can alleviate some of these impacts, although these barriers will need to be higher (and therefore more expensive) in the future to keep out the rising seas.

Deluge danger
Harvey’s biggest effect is through its intense and prolonged rainfall. A low pressure system to the north is keeping Harvey over southern Texas, resulting in greater rainfall totals.

The rainfall totals are already remarkable and are only going to get worse.

We know that climate change is enhancing extreme rainfall. As the atmosphere is getting warmer it can hold more moisture (roughly 7% more for every 1℃rise in temperature). This means that when we get the right circumstances for very extreme rainfall to occur, climate change is likely to make these events even worse than they would have been otherwise. Without a full analysis it is hard to put exact numbers on this effect, but on a basic level, wetter skies mean more intense rain.

Houston, we have a problem
There are other factors that are making this storm worse than others in terms of its impact. Houston is the second-fastest growing city in the United States, and the fourth most populous overall.

As the region’s population grows, more and more of southern Texas is being paved with impermeable surfaces. This means that when there is extreme rainfall the water takes longer to drain away, prolonging and intensifying the floods.

Hurricane Harvey is likely to end up being one of the most costly disasters in U.S. history. It is also likely that climate change and population growth in the region have worsened the effects of this major storm.

Andrew King is Climate Extremes Research Fellow, University of Melbourne. This article is published courtesy of The Conversation (under Creative Commons-Attribution / No derivative).