Precipitation–Climate Impacts CIRC 1.0 Final Report

Precipitation:

Precipitation projections for the Pacific Northwest don’t share the same level of certainty, or confidence, as temperature projections. Unlike temperature projections, there isn’t a consensus that our region will become either notably wetter or drier under human-caused climate change. What the climate models do suggest, taken together, is that annual precipitation might stay about the same or become slightly wetter (a small majority of models say wetter, some say drier). At the same time, our region’s summers might become slightly drier while our winters might become slightly wetter.

(For a general explanation of confidence levels and precipitation projections, see our webpage: http://pnwcirc.org/science/precipitation.)


OSU_icon_bulb_Black Key Findings:

  • Annual Precipitation: Under climate change, total yearly precipitation in the Pacific Northwest is not expected to deviate significantly from its current pattern, according to our RISA Team’s analysis. This means natural climate variability is expected to continue to play a large role in how much precipitation the Pacific Northwest receives on a yearly basis (Rupp, et al. 2016, adapted).
  • Seasonal Precipitation: The Pacific Northwest’s already wet winters might become slightly wetter and its already dry summers might become slightly drier as the region’s climate continues to change, according our analysis (Rupp, et al. 2016, adapted).

OSU_icon_graph_01Figures:

Annual, Winter, and Summer Precipitation Projections for the Pacific Northwest to the Year 2100

AnnualPrecipPNWFutureprojection
Annual precipitation simulations for the Pacific Northwest to the year 2100. The data show a slight increase in annual precipitation. However, this increase does not represent a large departure from the historical norm. The dashed zero line represents average annual precipitation for our region for roughly the second half of the 20th century. The gray section represents simulations of the historical period. The light and dark blue colors denote two emissions scenarios: RCP 4.5, a middle-of-the-road emissions scenario that leads to slower growth and eventually a leveling off of temperatures; and RCP 8.5, a high-emissions scenario that leads to a steady upward trend in temperatures. (For more info on emission scenarios, see our brief description on our website: http://pnwcirc.org/science/pathways.) Note: these precipitation projections have a low degree of confidence to them. This can be seen in how the light and blue shaded areas span both negative and positive values. Also, there isn’t a significant difference between either of the two emissions scenarios. (Figure source: David Rupp; data source: Rupp, et al. 2016)
Screen Shot 2015-04-27 at 10.18.29 AM
Winter precipitation projections for the Pacific Northwest to the year 2100. Note the slight upward trend in precipitation and how it deviates modestly from the historical average. Keep in mind these projections have a low degree of confidence to them. The winter simulations shown here were run using two emissions scenarios, RCP 4.5 (light blue) and RCP 8.5 (dark blue). These two scenarios represent medium and high degrees of warming respectively. Note: there isn’t a significant difference between either of the two emissions scenarios as far as winter precipitation is concerned. The gray section represents a simulation of the historical period. (Rupp et al. 2016, adapted.)
Screen Shot 2015-04-27 at 10.17.42 AM
Summer precipitation projections to year 2100. Note: there is a modest downward trend in summer precipitation that only slightly deviates from the historical norm. Keep in mind also that these projections have a low degree of confidence to them. As with the previous graph, light blue represents the medium-emissions scenario, RCP 4.5, while dark blue represents the high-emissions scenario, RCP 8.5. Note: there isn’t a significant difference between either of the two emissions scenarios. The historical period is shown in gray. (Rupp et al. 2016, adapted.)

OSU_icon_arrowleft_01Main Article


OSU_icon_gears_Black  Resource:


OSU_icon_pencil_Black Rotated Key Publications:

  • Abatzoglou, John T., David E. Rupp, and Philip W. Mote. “Seasonal Climate Variability and Change in the Paci c Northwest of the United States.”
    Journal of Climate 27, no. 5 (2014): 2125-2142.
    https://doi.org/10.1175/ JCLI-D-13-00218.1.
    Rupp, David E., John T. Abatzoglou, Katherine C. Hegewisch, and Philip W. Mote. “Evaluation of CMIP5 20th Century Climate Simulations for the Paci c Northwest USA.” Journal of Geophysical Research: Atmospheres 118, no. 19 (2013). https://doi.org/10.1002/jgrd.50843.
  •  Rupp, David E., John T. Abatzoglou, and Philip W. Mote. “Projections of 21st Century Climate of the Columbia River Basin.” Climate Dynamics (2016): 1-17. https://doi.org/10.1007/s00382-016-3418-7.

OSU_icon_pencil_Black Rotated Full Report:

Screen Shot 2018-04-10 at 10.13.14 AM
Gilles, Nathan G., Josh Foster, Meghan M. Dalton, Philip W. Mote, David E. Rupp, John Stevenson, Katherine A. Serafin, Janan Evans-Wilent, Peter Ruggiero, John T. Abatzoglou, Timothy J. Sheehan, Katherine C. Hegewisch, Denise H. Lach, Jessica Andrepont, and Kathie D. Dello. Responding to Climate Variability and Change in the Pacific Northwest United States: the Pacific Northwest Climate Impacts Research Consortium, September 2010–August 2017 Phase 1 Final Report. the Pacific Northwest Climate Impacts Research Consortium (CIRC), a NOAA RISA team. Corvallis, Oregon: College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, 2017.


OSU_icon_arrowleft_01Main Article


Nathan Gilles is the managing editor of The Climate Circulator, and oversees CIRC’s social media accounts and website. When he’s not writing for CIRC, Nathan works as a freelance science writer. Other Posts by this Author. 


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