Science Source
The Third Oregon Climate Assessment Report – January 2017
- Finds that key climate risks vary across Oregon
- In the Willamette Valley, declining snowpack, earlier snowmelt, and greater summer water demand may increase summer water scarcity; and wildfire activity is expected to increase.
- In the Cascade Range, diminishing snowpack leads to larger, earlier peak flow events and lower summer low flows; more wildfires and changes in climate suitability may shift forest vegetation types.
- In Eastern Oregon, declining snowpack has similar effects; warming streams will limit ranges for salmon and trout; disturbances and changes in suitability are expected to shift forest vegetation; and rangeland and sagebrush habitat may experience greater invasion of non-native weeds and more frequent fires.
- States that scientists formally linked climate trends and events to human activity
- Human emissions of greenhouse gases dominated the warming trend of average annual temperature in the Pacific Northwest during 1901–2012, contributed an additional 16,000 square miles of wildfire burned area in the western United States during 1984–2015, contributed to the 2014–2015 snow drought in Oregon through warmer temperatures, and made Oregon’s coastal waters more acidic in 2013.
- Finds that the 2015 snow drought foreshadows mid-century normal conditions
- Oregon’s warmest winter on record, 2015, was so warm that the near-normal amount of precipitation fell as rain in most of the mountains, resulting in record low snowpack and widespread drought declarations. Impacts included insufficient water supply in reservoirs, the most severe wildfire season in the Pacific Northwest’s history, warm streams that reduced salmon returns, and agricultural crop losses. With continued warming, this type of drought is
- Finds that warming is already changing hydrology
- Summer low flows have decreased and streamflow timing has shifted earlier at many sites in the Pacific Northwest. Driven by loss of snowpack and drier summers, these trends are expected to continue in the future, particularly for snow-dominated basins. As snowfall gives way to rainfall, fall and winter flood risk is also expected to increase in most basins, particularly in mixed rain-snow basins with near-freezing winter temperatures. Future changes in water supply and demand are expected to strain the ability of existing infrastructure and operations to meet all the varied water needs of Oregonians.
