Climate Science & Impacts

During the twentieth century the Pacific Northwest warmed by 0.7 degrees Celsius (roughly 1.3 degrees Fahrenheit), according to CIRC research. That warming has continued in recent years and is expected to continue throughout this century.

Our research indicates that by the year 2100 the Pacific Northwest is likely to be anywhere from 1 to 8 °C (2–15 ° F) warmer than it was during the second half of the twentieth century. This warming is expected to have a series of cascading effects on our landscapes, producing impacts as varied as winter flooding, summer drought, larger and more frequent wildfires, and rising sea levels.

This section of our website is intended as a kind of primer, outlining what our research says about some of these impacts. The section is also intended to demystify how our climate and social science research is conducted. This is why, whenever possible, we describe both our results as well as the methods we used to arrive at those results.

Climate impacts are effects on human communities and natural systems that result from changes in the climate. Climate impacts can result from anthropogenic (or human-caused) climate change, such as the notable long-term increase in average annual air temperatures in recent decades, or from natural climate variability, such as flooding connected to periodic El Niño and La Niña events. Climate impacts and our findings around them are listed by impact.


CIRC research indicates that by the year 2100, the Pacific Northwest could be anywhere from 1 to 8 °C (2–15 ° F) warmer than it was during the second half of the twentieth century.

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Confidence in projected precipitation for the Pacific Northwest is lower than confidence in temperature projections. We explain what that means, why annual precipitation might stay about the same or nudge slightly wetter, how our region’s summers might nudge slightly drier while our winters might nudge slightly wetter, and why all of this needs to be framed within pretty strict statistical wording.

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Snowpack, Hydrology, & Drought

Rising temperatures in the Pacific Northwest are changing our region’s hydrology, causing more precipitation to fall as rain and less as snow. This change has already led to water scarcities in the region. These scarcities are expected to continue in the future as our climate warms.

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Wildfires & Changing Vegetation

Rising temperatures are expected to make conditions ideal for larger, more destructive wildfires here in the Pacific Northwest. These fires, along with other disturbances, are expected to change the types of trees and other vegetation found in our region.

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Coastal Hazards & Extremes

A combined threat of rising sea levels, intensifying waves, and major El Niños has led to increased flooding and erosion hazards along the Pacific Northwest Coast. Learn the basics about hazards and extremes along our coast as our climate changes.

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Human Choice, Warming, & Emissions

More emissions of CO2 and other greenhouse gases spells more warming for our climate. That much is clear. What isn’t clear is how much more emissions, and thus warming, we can expect. Lucky for us, climate researchers have developed a kind of shorthand for this uncertainty: the Representative Concentration Pathways.

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The complexity associated with future climate impacts make it difficult, if not impossible, for communities to make long-term decisions. At CIRC, we’ve taken on this "wicked problem" by employing a social science approach called the coproduction of knowledge. This section describes the social science underpinning CIRC's Community Adaptation efforts. 

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Modeling & Analysis

To understand Earth’s complex processes, researchers employ powerful computer models. At CIRC we are working to advance the state of the science in modeling and analysis through our work with global climate models, regional climate models, hydrologic models, and vegetation models. We also do this thing called downscaling. Don't worry, we'll explain what all that means.  

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  Findings: Climate Impacts


  • By the year 2100 the Pacific Northwest is expected to be between 1 and 8 degrees Celsius (2–15 degrees Fahrenheit) warmer than it was during the second half of the 20th century, according to our research.


  • Using the latest climate models and scientific analysis, CIRC research was consistent with previous scientific findings suggesting that under climate change, yearly precipitation totals in the Pacific Northwest are not expected to deviate significantly from their current pattern. This means natural climate variability is expected to continue to play a large role in how much precipitation the Pacific Northwest receives on a yearly basis.

  • Our research was also consistent with previous findings suggesting that the Pacific Northwest’s already dry summers might become slightly drier as our region’s climate continues to change, while our already wet winters might become slightly wetter.

Snowpack & Drought:

  • CIRC research was consistent with and refined previous scientific analysis showing that rising temperatures resulting from anthropogenic climate change are altering the Pacific Northwest’s hydrology, causing precipitation to fall more as rain and less as snow.

  • The very warm temperatures the Pacific Northwest experienced during 2015 look similar to conditions that are projected to be “normal” by the middle of the 21st century, according to our research.

  • The water year 2015 was dubbed a “snow drought” because precipitation totals were at near normal levels while abnormally high temperatures led to record low snowpack.

  • Low snowfall years will become common in the Cascades by the middle of the 21st century, whereas high snowfall years will become exceedingly rare.

Wildfires & Ecological Change:

  • CIRC research was consistent with and refined previous analysis showing that wildfires have increased in size and frequency in the Western United States in recent decades.

  • Over half (55%) of the increase in fuel aridity conditions (the ability of vegetation to burn given the right ignition source) in recent years (1979–2015) is due to warming resulting from anthropogenic climate change, according to our research.

  • CIRC research was consistent with and refined previous analysis suggesting that tree types now common to parts of California are expected to migrate north, transforming many Pacific Northwest forests from conifer-dominant to mixed forests of both conifer and deciduous trees. This migration will be aided in some cases by fire.

Coastal Impacts:

  • Along the Pacific Northwest coast, El Niño events have been linked to an increase in coastal erosion of roughly 50% over typical winters, according to CIRC research.
  • The El Niño event of the winter of 2015–2016 resulted in the highest winter beach erosion on record for the West Coast.
  • Oregon’s beaches during the El Niño winter of 2015–2016 experienced erosion that surpassed by 30% the levels for the El Niño-free winter of 2014–2015.

  Findings: Modeling & Analysis

Global Climate Model Evaluation:

  • Data from global climate models that were the best statistical fit for the Pacific Northwest—that were best able to simulate the region’s historical climate—also projected the most warming for the region under climate change.

Multivariate Adaptive Constructed Analogs (MACA) Downscaling Method & Dataset:

  • MACA demonstrated its accuracy in capturing daily patterns of temperature and precipitation across the complex terrain of the western United States.

Regional Climate Modeling & Distributed Computing:

  • By the middle decades of the 21st century (2030–2049), warming winter and spring temperatures are expected to be greatest in the mountains—where mountain snowpack is already disappearing—than at the lower elevations.

Sensitivity-Based Approach to Modeling Watersheds:

  • The sensitivity-based approach was found to be comparable to the more computationally intensive full simulation approach in its ability to capture projected seasonality shifts in the hydrologic cycle at the watershed level.


  • The RISA coproduction model demonstrated new ways to develop usable information for complex or “wicked” problems, including climate change.