Friday, June 27, 2014

New paper finds global precipitation is increasing, decreasing, & not changing

Settled science: According to a paper published today in Atmospheric Science Letters, global precipitation has either decreased, increased, or not changed over the past 30 years, depending upon which of 3 global datasets are examined: 
"Decadal trends of global precipitation are examined using the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP), Global Precipitation Climatology Project (GPCP), and National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data. The decadal trends of global precipitation average diverge a decreasing trend for the CMAP data, a flat trend for the GPCP data, and an increasing trend for the reanalysis data." 
Thus, the actual trend of global precipitation, if any, remains a mystery. Several peer-reviewed papers have shown climate models are unable to simulate decadal trends in precipitation, unable to simulate regional trends in precipitation, and that the claim "wet gets wetter, dry gets drier" is without basis. 

Decadal trends of global precipitation in the recent 30 years

Xiaofan Li et al

Decadal trends of global precipitation are examined using the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP), Global Precipitation Climatology Project (GPCP), and National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data. The decadal trends of global precipitation average diverge a decreasing trend for the CMAP data, a flat trend for the GPCP data, and an increasing trend for the reanalysis data. The decreasing trend for the CMAP data is associated with the reduction in high precipitation. The flat trend for the GPCP data is related to the offset between the increase in high precipitation and the decrease in low precipitation. The increasing trend for the reanalysis data corresponds to the increase in high precipitation.

2 comments:

  1. My comment at the cross-post at WUWT:

    http://wattsupwiththat.com/2014/06/27/a-trifecta-of-uncertainty-study-finds-global-precipitation-is-increasing-decreasing-not-changing/#comment-1671529

    Hockey Schtick says:

    June 28, 2014 at 9:21 am

    A few comments asked about the “wet get wetter and dry get drier” meme…

    http://hockeyschtick.blogspot.com/2014/05/new-paper-finds-wet-get-wetter-and-dry.html

    New paper finds the “wet get wetter and dry get drier” meme is false on local scales

    An important paper published today in Hydrology and Earth System Sciences finds the claim that global warming causes wet regions to become wetter and dry regions to become drier is incorrect and “does not hold over water or land.” Instead, the authors find “in terms of P − E [precipitation - evaporation], the climate models do not project that the “wet get wetter and dry get drier” at the local scales that are relevant for agricultural, ecological and hydrologic impacts.”

    The “wet get wetter and dry get drier” meme had apparently not been checked on regional scales to which it is applied by the IPCC and climate scientists. According to the authors, “Much of the research on projected climate impacts has been based on an implicit assumption that this CC [Clausius–Clapeyron] relation [the basis for the "wet get wetter and dry get drier" meme] also holds at local (grid box) scales but this has not previously been examined. In this paper we find that the simple latitudinal average CC scaling relation does not hold at local (grid box) scales over either ocean or land.”

    According to the paper, “Much public and scientific perception about changes in the water cycle has been based on the notion that temperature enhances E [evaporation]. That notion is partly true but has proved an unfortunate starting point because it has led to misleading conclusions about the impacts of climate change on the water cycle. A better general understanding of the potential impacts of climate change on water availability that are projected by climate models will surely be gained by starting with the notion that the greater the enhancement of E [evaporation], the less the surface temperature increase (and vice versa). That latter notion is based on the conservation of energy and is an underlying basis of climate model projections.” In other words, the climate self-regulates with increases in temperature offset by increases in evaporative cooling [and vice-versa] to maintain temperatures within a homeostatic range.

    American Meteorological Society President Dr. Marshall Shepherd tweeted that one of his “toughest challenges” is “Explaining to linear thinkers that dry/drier, wet/wetter is expected. They want either or.” Perhaps this paper will explain to Dr. Shepherd why his superior non-linear thinking needs a reset on the “dry/drier, wet/wetter” meme that had not been verified on local/regional scales prior to the publication of this paper.

    See also:

    http://hockeyschtick.blogspot.com/2012/11/new-paper-contradicts-ipcc-assumptions.html

    http://hockeyschtick.blogspot.com/2012/11/new-paper-finds-models-have-it-wrong.html

    http://hockeyschtick.blogspot.com/2013/05/did-we-say-wet-becomes-wetter-and-dry.html

    ReplyDelete
  2. http://onlinelibrary.wiley.com/doi/10.1002/2013JD021167/abstract;jsessionid=921B443768B91613D80246AB6888F8CA.f03t02

    ReplyDelete