Global warming is well understood and accepted by the scientific community. Greenhouse gases at moderate levels are why the earth is warm enough to support life. But as we increase greenhouse gas concentrations in the atmosphere, we disturb the balance that has given us a moderate climate. We start overheating the planet. On this website you can see how climate change has already affected Oregon and what changes Oregon’s scientists are forecasting if we don’t reduce global greenhouse gas emissions.
The amount of warming occurring in the Pacific Northwest – about 1.5° F since 1920 – is consistent with what scientists would expect from the growth of global greenhouse gases accumulating in the atmosphere. Average temperatures are rising . . . which doesn’t mean there won’t continue to be colder and hotter days and years, but the colder days won’t be as cold, on average, and the hot days will be hotter still, on average.
No clear patterns of precipitation change have been discerned yet in the Pacific Northwest. Globally, warmer temperatures intensify the water cycle: more ocean evaporation, stronger winds, more precipitation when storms hit continental land masses.
Declines in spring snowpack in the Cascades have been observed, especially at low elevations, and the rise in greenhouse gases by itself probably has reduced spring snowpack by roughly 20%. Winter snows are melting earlier, especially at low-to-middle elevations. This has increased the risk of spring flooding, while reducing summer stream flows when fish and farmers both depend on those streams for water.
Land on the central and northern Oregon coast (from Florence to Astoria) is being affected by both subsiding coastal lands and rising sea levels, up about an inch every 15 years (sea level rises are offset in other areas by geologically-driven elevation gains of shorelines). This puts both low-lying communities and seashore ecosystems at risk.
The Next 10-50 Years
Scientists expect average temperatures in the Pacific Northwest will continue to rise in response to global climate change, by at least 1.5° F and as much as 2.7° F by 2030 and 5.4° F by 2050. These projected increases are likely to result in longer growing and fire seasons (and more fuel for fires), earlier animal and plant breeding, a longer and more intense allergy season and broad ecosystem disruption.
Precipitation changes are very uncertain, but most precipitation will continue to arrive in the winter. Lower summer precipitation and earlier peak stream flow will mean less water available for summer use, the risk of higher and more intense flooding, and decreased water quality due to higher temperatures, pollutant concentration, and increased salinity in coastal areas.
Sea levels will continue to rise. Higher levels could combine with stronger storms to accelerate coastal erosion, threatening communities and infrastructure such as Highway 101. Sea water intrusions may disrupt coastal wetland ecosystems.
Snowpack declines will continue and likely intensify, with effects on fish and adjacent ecosystems, irrigated agriculture, hydropower and flood control, and winter recreation.
Changes in ocean circulation patterns will likely intensify, affecting marine animals and vegetation. Effects on ocean water composition – acidification, low-oxygen zones – are already being measured and are expected to continue with consequences that remain difficult to predict.
Land and Stream Ecosystems
Effects are difficult to forecast with precision, but are likely to include migration of plant and animal species northward (or upward in elevation), with extinctions where migration is not an option. Anticipated drier summers will likely increase droughts, with threats to stressed forests from insects, disease and fire. Fire will be a greater threat to these ecosystems, as well as to many rural communities.
[Information derived from the Scientific Consensus Statement on the Likely Impacts of Climate Change on the Pacific Northwest – a product of a scientific meeting held in 2004 called the Impacts of Climate Change on the Pacific Northwest; and from consultation with the Oregon Climate Change Research Institute.]