Thomas R. Knutson Interview

#149 Great.com Talks With... Thomas R. Knutson from GDFL at NOAA

Records of tropical storm activity trace back as far as the 1800s, including weather observations from land and ship reports, as well as reports on hurricanes and storms collected in archival documents and newspapers. This information, however, is not as accurate or complete as scientists would like to have in order to test climate models and theories.  These models and theories are in turn used  to make future climate projections. Relatively stable satellite-based records of hurricane intensity only date back to around 1980, so in fact we only have 40 years’ worth of data to study for emerging signs of human-caused trends in hurricane intensity and related measures . Tom Knutson is a senior scientist and leader of the Weather and Climate Dynamic Division within GFDL. His work focuses on the impact of human-caused climate change on hurricanes and tropical storms, as well as detection of human-caused climate change in general.  

In the discussion surrounding tropical cyclones and climate change, there are two prominent questions at hand: have we identified a human imprint on hurricane activity based on past observations? And what changes can we expect in the frequency and strength of the storms moving forwards? These questions are of course linked, and lead to the bigger issue of the effects of global warming on current and future weather patterns. Knutson explains that the question of human impact on hurricane activity is a difficult one to answer. It is clear from longer-term data collected that sea levels are rising and global mean temperature has increased. And the sea level rise is leading to greater flood risk from storms at the coast, even if we assume storms themselves are not changing with climate change; the latter being a more difficult issue to address.  That is, for hurricane activity, it is much harder to identify a clear human influence in the past data than it is for global mean temperature, for example. 

The most confident statement about climate change influence on hurricanes, according to a recent assessment of the science is an   expectation that hurricanes will have higher rainfall rates in the warmer climates due to the increased levels of moisture in the atmosphere. Rains associated with tropical cyclones are an important component of risk; they can cause tremendous damage and loss of life due to flooding, especially when they hit underdeveloped or vulnerable areas of the world. Current modeling studies project an average increase of 10-15% for rainfall rates within 100km of the storm, under a 2 degree Celsius global warming scenario.  A 5% increase in hurricane intensity is also projected for the 2 degree warming scenario, as is an increase in the proportion of hurricanes that reach category 4 or higher intensity (i.e., very intense storms).

So how does this research make its way into a language that we can all understand and more crucially, into government policies in order to raise awareness and design effective prevention procedures? The Intergovernmental Panel on Climate Change (IPCC) assessments are published about every six years to take stock of the state of scientific research on climate change.  The report includes a summary for policymakers, which puts the main conclusions of the report into digestible terms, forming a vital communication link from the scientists to policy makers. These scientific assessments are vital for accessing the whole field of climate change science that is emerging, including observational evidence, modeling evidence, and an assessment of what detectable human influences are emerging and how consistent models are with the observed changes in climate. 

Moving forwards we  trust that the IPCC and other assessment reports be able to maintain a clear line of communication about climate change between the scientists conducting the research and the government/policy makers, and the general population. 

Listen to the whole interview for additional ways tropical cyclones can impact climate change. You can also read the Climate Special Science Report and check out NOAA’s news section.

Want to learn more about GFDL/NOAA? You can check out their current research projects, learn more about their climate models. 

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