A historical record of Pacific Northwest (defined here as west of the Cascade Mountains in Washington and Oregon) heat waves is identified using the U.S. Historical Climate Network, version 2, daily data (1901–2009). Both daytime and nighttime events are examined, defining a heat wave as three consecutive days above the 99th percentile for the maximum and minimum temperature anomalies separately. Although the synoptic characteristics of the daytime and nighttime heat events are similar, they do indicate some differences between the two types of events. Most notable is a stronger influence of downslope warming over the Cascade Mountains for the daytime events versus a more important role of precipitable water content for the nighttime events, presumably through its impact on downward longwave radiative fluxes. Current research suggests that the frequency and duration of heat waves are expected to increase in much of the United States, and analysis of the heat events reveals that a significant, increasing trend in the frequency of the nighttime events is already occurring in the Pacific Northwest. A heat wave occurred in 2009 that set all-time-record maximum temperatures in many locations and ranked as the second strongest daytime event and the longest nighttime event in the record.

Introduction: Western climate science and Traditional Ecological Knowledge (TEK) represent complementary and overlapping views of the causes and consequences of change. In particular, observations of changes in abundance, distribution, phenology, or behavior of the natural environment (including plants and animals) can have a rich cultural and spiritual interpretation in Indigenous communities that may not be present in western science epistemologies.Results: Using interviews with Indigenous elders and other Traditional Knowledge holders, we demonstrate that assumptions about the nature, perception, and utilization of time and timing can differ across knowledge systems in regard to climate change. Conclusions: Our interviewees' focus on relationality predisposes them to notice interactional changes among humans and other species, to be sensitive to smaller scale examples of change, to be more likely to see climate change as part of a broader time scale, and to link changes to a greater suite of socio-political phenomena, including the long arc of colonialism. One implication of this research and the interactions among humans and other species is that policies restricting Native and non-Native access to resources (i.e., hunting and fishing) to certain calendar seasons may need to be revisited in a changing climate.

[1] Water scarcity may appear to be a simple concept, but it can be difficult to apply to complex natural-human systems. While aggregate scarcity indices are straightforward to compute, they do not adequately represent the spatial and temporal variations in water scarcity that arise from complex systems interactions. The uncertain effects of future climate change on water scarcity add to the need for clarity on the concept of water scarcity. Starting with a simple but robust definition-the marginal value of a unit of water wehighlight key aspects of water scarcity and illustrate its many biophysical and socioeconomic determinants. We make four central observations. First, water scarcity varies greatly across location, time, and a multitude of uses that are valued either directly or indirectly by society. Second, water scarcity is fundamentally a normative, anthropocentric concept and, thus, can and should be distinguished from the related, purely descriptive notion of water deficit. While such an anthropocentric perspective may seem limiting, it has the potential to encompass the vast range of interests that society has in water. Third, our ability to understand and anticipate changes in water scarcity requires distinguishing between the factors that affect the value or benefits of water from those affecting the costs of transforming water in space, time and form. Finally, this robust and rigorous definition of water scarcity will facilitate better communication and understanding for both policymakers and scientists.

This report, required by state law under HB3543, provides a comprehensive assessment of the state of science of climate change as it pertains to Oregon, covering the physical, biological, and social dimensions. The first chapter summarizes the current state of knowledge of physical changes in climate and hydrology, focusing on the period since the previous Oregon Climate Assessment Report (OCAR3, Dalton et al. 2017); and the second chapter covers the impacts. The second chapter is, verbatim, the Northwest chapter of the Fourth National Climate Assessment (NCA4) which was released by the federal government November 23, 2018. It is available for download separately: https://nca2018.globalchange.gov/downloads/NCA4_Ch24_Northwest_Full.pdf

The group of scientists that make up the Intergovernmental Panel on Climate Change found in 2007 that the warming of Earth’s climate is unequivocal and largely due to human activity. Earth’s climate has changed in the past, though the recent magnitude and pace of changes are unprecedented in human existence. Recent decades have been warmer than at any time in roughly 120,000 years. Most of this warming can be attributed to anthropogenic activity, primarily burning fossil fuels (coal, oil and natural gas) for energy. Burning fossil fuels releases carbon dioxide and other heat trapping gases, also known as greenhouse gases, into the atmosphere. This warming cannot be explained by natural causes (volcanic and solar) alone. It can be said with confidence that human activities are primarily responsible for the observed 1.5 ˚F increase in 20th century temperatures in the Pacific Northwest. A warmer climate will affect this state substantially. In 2007, the Oregon State Legislature charged the Oregon Climate Change Research Institute, via HB 3543, with assessing 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 the state. This inaugural assessment report is meant to act as a compendium of the relevant research on climate change and its impacts on the state of Oregon. This report draws on a large body of work on climate change impacts in the western US from the Climate Impacts Group at the University of Washington and the California Climate Action Team. In this report, we also identify knowledge gaps, where we acknowledge the need for more research in certain areas. We hope this report will serve as a useful resource for decision-makers, stakeholders, researchers and all Oregonians. The following chapters address key sectors that fall within the biological, physical and social sciences in the state of Oregon.