Abstract

Consistent with its charge under Oregon House Bill 3543, the Oregon Climate Change Research Institute (OCCRI) conducts a biennial assessment of the state of climate change science, including biological, physical, and social science, as it relates to Oregon and the likely effects of climate change on Oregon.

This sixth Oregon Climate Assessment builds on the previous assessments by continuing to evaluate past and projected future changes in Oregon’s climate and water supply. Like the fifth assessment, it is structured with the goal of supporting the state’s mitigation planning for natural hazards and implementation of the 2021 Oregon Climate Change Adaptation Framework.

The first section of this assessment, State of Climate Science, reflects OCCRI’s sustained appraisal of observed trends and future projections of temperature, precipitation, and other major climate variables. Previous key messages about projected changes in Oregon’s climate, such as warmer temperatures, drier summers, and an increase in the frequency, duration, and severity of drought, remain consistent. State of Climate Science summarizes emerging evidence related to potential effects of Arctic warming on the state’s climate and explores the likelihood of changes in annual and seasonal wind speeds. The section also compares the latest two generations of global climate models, including their assumptions about emissions of greenhouse gases and their accessibility.

The second section of this Oregon Climate Assessment delves into the expected effects of climate change on natural hazards, including extreme temperatures, drought, changes in the water cycle, wildfire, and coastal flooding and erosion. Glaciers and perennial snowfields in Oregon retreated rapidly during the past 30 years, reducing storage of water that otherwise would be released during late summer. The section details the contributions of tens of thousands of weather stations to PRISM, the most widely used source of mapped climate data in the United States, and explains how public participation in science is becoming a powerful means of filling data gaps and improving models of precipitation and water availability. The increasing incidence and size of wildfires, whether ignited by human activity or lightning, are strongly linked to episodic drought and longterm increases in aridity. Two surveys conducted after extensive wildfires in 2020 suggest relatively high support among Oregonians for climate mitigation and adaptation policies. Survey results also indicate widespread concerns about the impacts of smoke on personal health and desires for greater access to smoke-related information and protective equipment.

The third section of this assessment addresses six sectors within which Oregon’s 2021 Climate Change Adaptation Framework aggregates vulnerabilities and strategic responses: economy, natural world, built environment and infrastructure, public health, cultural heritage, and social systems. The section begins with a robust discussion of economic concepts and tools relevant to understanding climate challenges and opportunities, and highlights recent insights on the effects of climate change on economic activity in Oregon. Contributions related to natural systems underscore that observations of short-term ecological stress from climate extremes, such as foliage scorch, may or may not indicate long-term effects on mortality and nutrient and water cycles. Furthermore, new research questions whether salmonids in the Pacific Northwest may be more tolerant of high water temperatures than previously assumed. Next, the section investigates how reforms of Oregon’s landuse and housing laws are supporting reduction of greenhouse gas emissions, increases in community resilience, and more-equitable distribution of environmental benefits and burdens.

Contributions related to public health in this assessment concentrate on the effects of wildfire smoke on human health and the health care system, and the fact that wildfire smoke and high 10 surface ozone levels increasingly tend to occur on the same days during summer. The health risks of exposure to fine particulate matter (PM2.5) are fairly well understood, but many other uncertainties remain, such as the health effects of repeated smoke exposure and relations between health responses and the composition of smoke. Early career tribal citizens share the ways in which their communities are responding to climate change, exercising self-determination and reclaiming sovereignty despite historic and contemporary inequities. The section also explores how visual artists are communicating with the public about climate change, engaging audiences in conversation and encouraging creative problem-solving. Furthermore, the section examines regenerative agriculture, an increasingly popular set of practices that aims to restore and sustainably manage degraded soils.

Both the Climate Change Adaptation Framework and this assessment recognize that the myriad interactions and feedbacks among natural and human systems are complex and can be difficult to differentiate. An iterative assessment process can indicate the extent to which natural hazards may affect adaptation sectors, and inform selection of actions to maximize livelihoods and well-being.