Climate Change in the Northwest: Implications for Our Landscapes, Waters, and Communities is aimed at assessing the state of knowledge about key climate impacts and consequences to various sectors and communities in the northwest United States. It draws on a wealth of peer-reviewed literature, earlier state-level assessment reports conducted for Washington (2009) and Oregon (2010), as well as a risk-framing workshop. As an assessment, it aims to be representative (though not exhaustive) of the key climate change issues as reflected in the growing body of Northwest climate change science, impacts, and adaptation literature now available.

This report will serve as an updated resource for scientists, stakeholders, decision makers, students, and community members interested in understanding and preparing for climate change impacts on Oregon, Washington, and Idaho. This more detailed, foundational report is intended to support the key findings presented in the Northwest chapter of the Third National Climate Assessment. 

CHAPTER 1

Introduction

The Changing Northwest

AUTHORS Amy K. Snover, Patty Glick, Susan M. Capalbo

Human influences on climate, already apparent at the global and continental scales (IPCC 2007), are projected to alter the climate, ecology and economy of the Northwest (NW). Despite large natural variations, changes in regional temperature, snowpack, snowmelt timing, and river flows have already been observed that are consistent with expected human-caused trends (Mote 2006; Pierce et al. 2008; Stewart et al. 2005; Hidalgo et al. 2009; Luce and Holden 2009). With 21st century rates of global and regional warming projected to be at least double those observed in the 20th century (IPCC 2007; Mote and Salathé 2010; see Chapter 2), these changes are expected to continue even as new changes emerge.

Climate change is projected to alter environmental conditions across the region, affecting the Northwest's natural resource base and changing habitat conditions for fish and wildlife. The regional consequences of climate change will pose new risks to health, safety, and personal property, alter the reliability of transportation interconnections, and drive changes in local and regional economies. More fundamentally, these changes mean that many of the climatic assumptions inherent in decisions, infrastructure, and policies across the Northwest—from where to build, to what to grow where, to how to manage variable water resources to meet multiple needs—will become increasingly incorrect.

Many of the changes set in motion are unavoidable, caused by greenhouse gases already emitted (Solomon et al. 2009), though they may be temporarily obscured by the Northwest's highly variable climate (Hawkins and Sutton 2009; Deser et al. 2012). What risks will a changing climate bring for the region as a whole and for specific sectors and locations? What strategies are emerging for evaluating and altering management of regional water and energy supplies, infrastructure, transportation, health, and ecological and agricultural systems to address these risks? To what extent is the region preparing?

This report synthesizes currently available information to provide answers to these questions. It focuses on impacts that matter for the region as a whole, chosen with an eye toward the likely major drivers of regional change and consequences of highest regional and local importance. It is an assessment of existing knowledge that builds on and augments previous assessments (e.g., Climate Impacts Group 2009, Oregon Climate Change Research Institute 2010) and draws on a wealth of resources from local government and state agency reports to academic peer-reviewed journal articles. It is intended to be a resource for preparing the Northwest for climate change.

While we can do our best to discern the most likely consequences of climate change for NW ecosystems and communities, the ultimate consequences of the changes now in motion remain partially contingent on future societal actions and choices. Whether the consequences of the climate impacts outlined in this report are severe or mild depends in part on the degree to which regional social, economic, and infrastructural systems are adjusted to align with the changing climate, and the degree to which natural systems are provided with the room, flexibility, and capacity to respond. The regional consequences of climate change will also be strongly shaped by past choices—of what to build where, what to grow where—and by the laws, institutions, and procedures that shape how natural resources are managed and allocated, risks from natural hazards are identified, and trade-offs among conflicting objectives resolved.

This chapter sets the stage for the detailed, sector-specific examination of climate risks that follow. It provides an introduction to the physical, ecological, and economic characteristics of today's Northwest, describes the risk assessment methods used to prepare this report, comments on common themes about future change that cross all sectors, and describes the current state of regional preparation for climate change.

1.1 Regional Introduction: The Physical, Ecological, and Social Template

Bordering Canada and the Pacific Ocean, comprising the states of Washington, Oregon, and Idaho, and including boundary-spanning watersheds like the Columbia River basin (fig. 1.1), the Northwest is a region defined in large part by its landscape and abundant natural resources. With craggy shorelines, volcanic mountains, and high sage deserts, the Northwest's complex and varied topography contributes to the region's rich climatic, ecological, and social diversity. Natural resources—timber, fisheries, productive soils, and plentiful water—remain important to the region's economy and strong connections to the environment are common. These regional characteristics set the stage for current and future regional climate vulnerabilities.

1.1.1 LANDSCAPE AND CLIMATE

Lying between the Pacific Ocean and the Rocky Mountains and punctuated by the Cascade and Olympic mountain ranges, the Northwest experiences a Mediterranean-type climate with relatively wet winters and dry summers. The mountains enhance winter precipitation, with some of the wettest locations in North America found on the west slopes of the Olympic Mountains where annual precipitation over 16.4 feet (5 meters) of water equivalent, supports the region's dramatic coastal temperate rainforest. In contrast, the lee side of the Cascade Range is much drier, with desert-like conditions occurring on the high plateau of the interior Columbia Basin where annual precipitation can be less than 8 inches (20.3 cm) (Jackson and Kimmerling 1993; see fig. 2.1).

With 453 miles (729 km) of coastline and 4,436 miles (7139 km) of tidal shoreline (including Puget Sound and the Columbia River estuary; US Department of Commerce et al. 2009), the NW coast spans seven degrees of latitude. Coastal mountains, strong Pacific currents, and diverse coastal landforms—including rocky shores, hilly headlands and sandy beaches, broad coastal plains, and barrier beaches and dunes—create varied and diverse coastal environments next to some of the most productive coastal waters in the world (Good 1993).

1.1.2 ECOSYSTEMS, SPECIES, AND HABITATS

Together, Washington, Oregon, and Idaho constitute one of the most ecologically rich areas in the United States, reflecting the region's topographically induced climatic diversity. The region contains diverse species and habitats, ranging from the sage grouse and pygmy rabbits that rely on the shrub steppe habitats of southern Idaho and the Columbia...