Hurricane Harvey: Connecting the dots between climate change and more extreme events

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Climate Code Red

The science of attributing extreme weather to climate change is complicated and developing every day. Here’s a guide of what we know about the links between climate change and Harvey to help unpack the elements that contributed to this historic and unfolding storm. For a complete annotated backgrounder, visit the related events page on Climate Signals.

hurricane harvey.


As seas warm, more water evaporates to the atmosphere. A warmer atmosphere can hold more water, fueling extreme rainfall and increasing flood risk. Record-breaking rainfall is a classic signature of climate change, and the fingerprint of climate change has been firmly identified in the observed global trend of increasing extreme precipitation.

  • Many areas of Southeast Texas have received rain so extreme that historical data indicates it should only happen once every 1,000 years.
  •  Houston is experiencing its third ‘500-year’ flood in 3 years.
  •  Since the 1950s, Houston has seen a 167 percent increase in the frequency of the most intense downpours.
  •  A rain gauge in Mont Belvieu, about 40 miles east of Houston, registered 51.88 inches of rain through late afternoon Tuesday. Once verified, this amount would break not only the Texas state rainfall record but also the record for the remaining Lower 48 states.
  •  A formal attribution study of last year’s historic flood in Louisiana found that climate change to date had most likely doubled the frequency of the extreme rainfall that drove that flood.
  • Kevin Trenberth, a senior scientist at the U.S. National Center for Atmospheric Research, said, “The human contribution can be up to 30 percent or so of the total rainfall coming out of the storm.”

Stalled weather

Another major contributor to the extreme rainfall totals was that Harvey stalled for many days over southeast Texas. Waves in the jet stream can stall in place (instead of moving eastward), leading to blocking and persistent weather patterns that fuel the intensity and duration of rainfall events.

  • A study from March 2017 found that climate change is altering large scale weather patterns, such as the jet stream, which have the ability to dramatically amplify extreme weather events, such as extreme rainfall, during the summer.
  • According to Michael Mann, the stalled weather pattern during Hurricane Harvey “is precisely the sort of pattern we expect because of climate change.”

Sea level rise

Sea level rise has significantly extended the reach of storm surge and coastal flooding driven by hurricanes.


The warmer the waters, the more energy available to passing storms, increasing the risk of major hurricane development. Climate change also affects other factors that shape and control hurricane development, such as wind shear. The balance of all these factors is not fully known. However, hurricanes have grown stronger over recent decades. And there is a significant risk global warming may be driving that trend.

Rapid intensification

There is an observable trend toward increasingly rapid intensification of hurricanes, leaving less time to prepare. There is a significant risk that this trend is driven by global warming.

Source: Climate Code Red. Reproduced with permission.  

  • trackdaze

    Im afraid it will take a couple of harveys in quick succession for the dots to be big enough for a (way too large) minority to see it.

  • Joe

    The description…’Climate Refugees’ can no longer be laughed off. Texans will soon be joining the residents of Bangladesh, Miami, Kiribati, Tuvalu, Marshall Islands etc in searching for new homes that are not threatened from inundation.

    • networthless

      What utter swill! Houston was built in a swamp. Huge population increases and paving countless acres with concrete exacerbates the natural phenomenon.

      No dots to connect! Look up Indianola.

      • trackdaze

        3 500 year events in three years ought to be less likely than winning the lottery.