MSGID: 1:317/3 6459cc62   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Atmospheric research provides clear evidence of human-caused climate   
   change signal associated with CO2 increases    
    Claims that climate change is natural are inconsistent with atmospheric   
   temperature trends    
      
     Date:   
         May 8, 2023   
     Source:   
         Woods Hole Oceanographic Institution   
     Summary:   
         New research provides clear evidence of a human 'fingerprint' on   
         climate change and shows that specific signals from human activities   
         have altered the temperature structure of Earth's atmosphere.   
      
      
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   FULL STORY   
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   New research provides clear evidence of a human "fingerprint" on climate   
   change and shows that specific signals from human activities have altered   
   the temperature structure of Earth's atmosphere.   
      
   Differences between tropospheric and lower stratospheric temperature   
   trends have long been recognized as a fingerprint of human effects on   
   climate. This fingerprint, however, neglected information from the mid   
   to upper stratosphere, 25 to 50 kilometers above the Earth's surface.   
      
   "Including this information improves the detectability of a human   
   fingerprint by a factor of five. Enhanced detectability occurs   
   because the mid to upper stratosphere has a large cooling signal from   
   human-caused CO2 increases, small noise levels of natural internal   
   variability, and differing signal and noise patterns," according to   
   the journal article, "Exceptional stratospheric contribution to human   
   fingerprints on atmospheric temperature," published in the Proceedings   
   of the National Academy of Sciences (PNAS). Noise in the troposphere   
   can include day-to-day weather, interannual variability arising from El   
   Nin~os and La Nin~as, and longer-term natural fluctuations in climate.   
      
   In the upper stratosphere, the noise of variability is smaller, and the   
   human- caused climate change signal is larger, so the signal can be much   
   more easily distinguished.   
      
   "Extending fingerprinting to the upper stratosphere with long temperature   
   records and improved climate models means that it is now virtually   
   impossible for natural causes to explain satellite-measured trends in   
   the thermal structure of the Earth's atmosphere," the paper states.   
      
   "This is the clearest evidence there is of a human-caused climate change   
   signal associated with CO2 increases," according to lead author Benjamin   
   Santer, an adjunct scientist in the Physical Oceanography Department at   
   the Woods Hole Oceanographic Institute (WHOI) in Massachusetts.   
      
   "This research undercuts and rebuts claims that recent atmospheric   
   and surface temperature changes are natural, whether due to the Sun or   
   due to internal cycles in the climate system. A natural explanation is   
   virtually impossible in terms of what we are looking at here: changes in   
   the temperature structure of the atmosphere," added Santer, who has worked   
   on climate fingerprinting for more than 30 years. "This research puts to   
   rest incorrect claims that we don't need to treat climate change seriously   
   because it is all natural."  The research was motivated by earlier   
   work by Suki Manabe and Richard Wetherald, who in 1967 used a simple   
   climate model to study how CO2 from fossil fuel burning might change   
   atmospheric temperature. Their modeling found a very distinctive feature:   
   an increase in CO2 levels led to more trapping of heat in the troposphere   
   (the lowest layer of Earth's atmosphere) and less heat escaping higher up   
   into the stratosphere (the layer above the troposphere), thus warming the   
   troposphere and cooling the stratosphere. This prediction of tropospheric   
   warming and stratospheric cooling in response to increasing CO2 has been   
   confirmed many times by more complex models and verified by comparing   
   model results with global-mean atmospheric temperature observations from   
   weather balloons and satellites.   
      
   Although these earlier studies considered global-mean temperature changes   
   in the middle and upper stratosphere, roughly 25 to 50 kilometers above   
   Earth's surface, they did not look at detailed patterns of climate change   
   in this layer. This region can be better studied now because of improved   
   simulations and satellite data. The new research is the first to search   
   for human-caused climate change patterns -- also called "fingerprints"   
   -- in the middle and upper stratosphere.   
      
   "The human fingerprints in temperature changes in the mid to upper   
   stratosphere due to CO2 increases are truly exceptional because they are   
   so large and so different from temperature changes there due to internal   
   variability and natural external forcing. These unique fingerprints   
   make it possible to detect the human impact on climate change due to   
   CO2 in a short period of time (~10 - - 15 years) with high confidence,"   
   stated co-author Qiang Fu, a professor in the Department of Atmospheric   
   Sciences at the University of Washington.   
      
   "The world has been reeling under climate change, so being as confident   
   as possible of the role of carbon dioxide is critical," said co-author   
   Susan Solomon, Martin Professor of Environmental Studies at the   
   Massachusetts Institute of Technology. "The fact that observations   
   show not only a warming troposphere but also a strongly cooling upper   
   stratosphere is unique tell-tale evidence that nails the dominant role   
   of carbon dioxide in climate change and greatly increases confidence."   
   Santer said that although it is intellectually gratifying to be able to   
   extend fingerprinting higher up into the atmosphere to test the prediction   
   by Manabe and Wetherald, it is also deeply concerning.   
      
   "As someone who tries to understand the kind of world that future   
   generations are going to inhabit, these results make me very worried. We   
   are fundamentally changing the thermal structure of Earth's atmosphere,   
   and there is no joy in recognizing that," Santer said.   
      
   "This study shows that the real world has changed in a way that   
   simply cannot be explained by natural causes," Santer added. "We now   
   face important decisions, in the United States and globally, on what   
   to do about climate change. I hope those decisions are based on our   
   best scientific understanding of the reality and seriousness of human   
   effects on climate."  Funding for the study was provided by National   
   Science Foundation, National Oceanic and Atmospheric Administration,   
   U.S. Department of Energy, and the Francis E. Fowler IV Center for Ocean   
   and Climate at Woods Hole Oceanographic Institution.   
      
       * RELATED_TOPICS   
             o Earth_&_Climate   
                   # Climate # Environmental_Awareness # Global_Warming   
                   # Atmosphere # Environmental_Issues # Weather #   
                   Environmental_Policy # Geoengineering   
       * RELATED_TERMS   
             o Attribution_of_recent_climate_change o   
             Consensus_of_scientists_regarding_global_warming   
             o Effects_of_global_warming o   
             Temperature_record_of_the_past_1000_years o Global_climate_model   
             o Global_warming o Global_warming_controversy o Water_resources   
      
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   Story Source: Materials provided by   
   Woods_Hole_Oceanographic_Institution. Note: Content may be edited for   
   style and length.   
      
      
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   Journal Reference:   
      1. Benjamin D. Santer, Stephen Po-Chedley, Lilong Zhao, Cheng-Zhi   
      Zou, Qiang   
         Fu, Susan Solomon, David W. J. Thompson, Carl Mears, Karl E. Taylor.   
      
         Exceptional stratospheric contribution to human fingerprints on   
         atmospheric temperature. Proceedings of the National Academy of   
         Sciences, 2023; 120 (20) DOI: 10.1073/pnas.2300758120   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230508190601.htm   
      
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