AGU Fall Meeting: Human-caused warming likely intensified Hurricane Harvey’s rains

13 December 2017


Included in this announcement:

  1. Research from the AGU Fall Meeting: Human-caused warming likely intensified Hurricane Harvey’s rains
  2. Today’s press events
  3. Noteworthy sessions happening today
  4. Potentially newsworthy presentations
  5. Online media resources

Please visit the 2017 Fall Meeting Media Center to view previous media advisories and press releases that include important information about press registration, badge pickup, press conferences, quiet rooms, searching the scientific program, and AGU On-Demand.

1. Research from the AGU Fall Meeting: Human-caused warming likely intensified Hurricane Harvey’s rains

The GOES-16 satellite captured this geocolor image of Hurricane Harvey at 8:02 a.m. CDT on August 26, 2017. New research finds human-induced climate change increased the amount and intensity of Hurricane Harvey’s unprecedented rainfall.
Credit: NOAA.

NEW ORLEANS — New research shows human-induced climate change increased the amount and intensity of Hurricane Harvey’s unprecedented rainfall. The new findings are being published in two separate studies and being presented in a press conference today at the 2017 American Geophysical Union Fall Meeting, along with additional new findings about recent Atlantic Ocean hurricanes.

Hurricanes Harvey, Irma and Maria battered the U.S. Gulf Coast and Caribbean earlier this year, bringing widespread flooding and wind damage. Hurricane Harvey, a Category 4 storm at first landfall on August 25, stalled over Texas as a tropical storm, causing record rainfall between August 26 and 28.

A new study accepted for publication in Geophysical Research Letters (GRL), a journal of the American Geophysical Union, finds Hurricane Harvey’s seven-day rainfall total potentially increased by at least 19 percent compared to a similar storm in the mid-20th century. Another study published online today in the journal Environmental Research Letters (ERL) directly attributes the rainfall increase to human-caused climate change. The ERL paper finds climate change made the record three-day rainfall that fell over Houston during Hurricane Harvey roughly three times more likely and 15 percent more intense than a similar storm in the early 1900s.

The new research confirms heavy rainfall events are increasing across the Gulf Coast region because of human interference with the climate system. Climate change, caused by increasing greenhouse gases in the atmosphere from the burning of fossil fuels, is raising temperatures globally. Warmer air can carry more moisture, which can lead to more extreme rainfall events, and warmer ocean surface temperatures are known to intensify the most powerful hurricanes.

In the GRL study, researchers used a statistical model based on historical climate data to separate how much of the extreme rainfall from Hurricane Harvey was due to natural influences and how much was due to human influences. They first estimated the chances of Harvey’s precipitation total at the present day then estimated the amount of precipitation that would have fallen in an event of the same rarity using 1950s greenhouse gas levels, essentially stripping away the effects of today’s higher greenhouse levels.

The study’s authors expected about a 6 percent increase in rainfall from Hurricane Harvey because of warming in the Gulf of Mexico. The new study finds human-induced climate change likely increased Hurricane Harvey’s unprecedented rainfall by at least 19 percent and potentially as much as 38 percent.

“It is not news that climate change affects extreme precipitation, but our results indicate that the amount is larger than expected,” said researcher Michael Wehner of Lawrence Berkeley National Laboratory in Berkeley, California, a co-author of the new GRL study, who will also be presenting the new research at a press conference at the AGU Fall Meeting today.

In the new study in ERL, researchers examined the observed rainfall record in the Gulf Coast region since 1880 to show that the intensity of extreme precipitation has increased substantially. Multiple high-resolution climate models confirmed that the increasing trend is due mainly to human-caused global warming.

Overall, the chances of seeing a rainfall event as intense as Harvey have roughly tripled – somewhere between 1.5 and five times more likely – since the 1900s and the intensity of such an event has increased between 8 percent and 19 percent, according to the new study by researchers with World Weather Attribution, an international coalition of scientists that objectively and quantitatively assesses the possible role of climate change in individual extreme weather events.

Even if global targets set by the Paris Agreement of limiting warming to 2 degrees Celsius (3.6 degrees Fahrenheit) are met, scientists estimate an event like Hurricane Harvey will see a further increase of about a factor of three in probability.

“But, if we miss those targets, the increase in frequency and intensity could be much higher,” said Karin van der Wiel, a postdoctoral researcher at the Royal Netherlands Meteorological Institute (KNMI) in De Bilt, Netherlands and a co-author of the new ERL paper, who will also be presenting the new research at a press conference today at the AGU Fall Meeting.

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Notes for Journalists
Study authors Michael Wehner and Karin van der Wiel will present this research in a two-part press conference on hurricanes Harvey, Irma and Maria at the AGU Fall Meeting on Wednesday, 13 December 2017 starting at 2:30 p.m. CST. See #2 below for information about the press conference and #3 below for information about related scientific sessions.

Paper Information:
Geophysical Research Letters: Attributable human-induced changes in the likelihood and magnitude of the observed extreme precipitation in the Houston, Texas region during Hurricane Harvey
This research article is open access for 30 days.

Environmental Research Letters: Attribution of extreme rainfall from Hurricane Harvey, August 2017
This research article is open access. 

Neither the papers nor this press release are under embargo.

Contact information for the authors:
Michael Wehner, [email protected], +1 (415) 305-1044
Mark Risser, [email protected]
Karin van der Wiel, [email protected]

2. Today’s press events

8:00 a.m. – The melting cryosphere
9:00 a.m. – Improving gender equity in the geosciences (Workshop)
10:30 a.m. – Spanning disciplines to search for life beyond Earth
11:30 a.m. – Explaining extreme events of 2016 from a climate perspective
12:30 p.m. – ** NEW ** The September 2017 Tehuantepec and Puebla earthquakes in Mexico
1:30 p.m. – Canary in the coalmine: Subsidence in coastal Louisiana
2:30 p.m. – Hurricanes Harvey, Irma and Maria – Part 1
3:30 p.m. – Hurricanes Harvey, Irma and Maria – Part 2

All Fall Meeting press events take place in the Press Conference Room, Room 346-347. They will also be streamed live on the AGU press events webpage and archived on AGU’s YouTube channel. Slides and other materials will be available in the Virtual Press Room on the Fall Meeting Media Center.

3. Noteworthy sessions happening today

Frontiers of Geophysics Lecture
Joanna Morgan, Professor of Geophysics at Imperial College London and Co-Chief Scientist of the IOPD-ICDP Expedition 364 Chicxulub Impact Crater Drilling Project, will deliver the Frontiers of Geophysics Lecture, “Chicxulub: The End of an Era,” from 12:30 – 1:30 p.m. in the New Orleans Theater, located on the second floor of the Morial Convention Center above Hall I-1. Registered journalists who are interested in attending this talk should meet an AGU staff member at the entrance to the lecture hall 30 minutes prior to the start of the talk. Journalists can also stream the lecture live on AGU On-Demand.

4. Potentially newsworthy presentations happening today

Late-breaking sessions

Sessions

  • Mitigating Flood Risk and Climate Change Impacts Through Managed Retreat
    Session U31A, 8:00– 10:00 a.m., Room E2
  • Atmospheric Impacts of Emissions from the Unconventional Oil and Gas Sector
    Session A31B, 8:00 a.m. – 12:20 p.m., Poster Hall D-F
    Session A34B, 4:00 – 6:00 p.m., Room 393-394

Abstracts

5. Online media resources

For journalists: During the Fall Meeting, journalists can find many resources online in the Virtual Press Room in the Fall Meeting Media Center. These resources include press releases, press conference materials and other information. Videos of press conferences will be added to the Virtual Press Room during the meeting for easy online access.

The AGU press office also offers two online tools to connect reporters with scientific experts at the 2017 Fall Meeting. The Find an Expert tool allows reporters to view a list of scientific experts who are available for interviews at the meeting. The Request an Expert tool allows reporters to send requests for experts directly to PIOs. These tools are now available online in the Fall Meeting Media Center.

For public information officers: PIOs are now able to share press releases and other materials in the Virtual Press Room by directly uploading them via the Press Item Uploader. PIOs can upload press releases, tip sheets and press conference materials to the Virtual Press Room at any time before or during the meeting, including uploading items in advance and scheduling them to post during the meeting.

The AGU press office also offers two online tools to connect reporters with scientific experts at the 2017 Fall Meeting. The Find an Expert tool allows public information officers to list scientific experts who are available to be interviewed by reporters at the meeting. The Request an Expert tool allows reporters to send requests for experts directly to PIOs. PIOs who wish to receive expert request emails from reporters should fill out the Receive Expert Requests form. More information about these tools can be found in the Fall Meeting Media Center.

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