Mar 12, 2018

Model Assessment of Observed Precipitation Trends Over Land Regions: Detectable Human Influences and Possible Low Bias in Model Trends

by
Thomas R. Knutson and Fanrong Zeng
,
AMS Journal of Climate
  • Assesses precipitation trends for 1901–2010, 1951–2010, and 1981–2010 over relatively well-observed global land regions for detectable anthropogenic influences and for consistency with historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5)
  • Finds that the CMIP5 historical all-forcing runs are broadly consistent with the observed trend pattern (1901–2010), but with an apparent low trend bias tendency in the simulations
  • Finds, despite this bias, that observed and modeled trends are statistically consistent over 59% of the analyzed area.
  • Finds that over 20% (9%) of the analyzed area, increased (decreased) precipitation is partly attributable to anthropogenic forcing, including: 
    • Increases over regions of the north-central United States, southern Canada, Europe, and southern South America and
    • Decreases over parts of the Mediterranean region and northern tropical Africa
  • Trends for the shorter periods (1951–2010 and 1981–2010) do not indicate a prominent low trend bias in the models, as found for the 1901–2010 trends