Chapter 6: Climate Vulnerability Assessment

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Salem is fortunate to have a mild climate—only 21 degrees separate the average annual maximum temperature of 63.1ºF from the average annual minimum temperature of 42.1ºF.10 While this mild baseline means that the changes to Salem’s temperatures due to climate change may be less extreme than other locations in the country, the City will nevertheless experience notable shifts in the future.

Climate change is already affecting Oregon. The Fifth Oregon Climate Assessment describes increasing temperatures, changes to precipitation patterns, increased risk of floods, and increasing risk of wildfire across the state.11 Since 1895, Oregon has already experienced an average temperature increase of 2.2°F per century. The state is on pace to see temperatures rise by an average of 5°F by mid-century and by an average of 8.2°F by the 2080s. Summer temperatures are projected to increase the most. Rising temperatures, combined with changes in precipitation patterns, may lead to hotter and drier conditions that increase the risk of wildfires across the state and in the Salem area.

How Climate Risk is Created

Figure 2. Source. IPCC, 2014: Summary for policymakers. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, et. al. Mastrandrea, et. al., (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1-32.


A critical step of the climate planning process is to take a close look at the specific ways that Salem will be affected by projected climate change impacts. This process helps to identify potential hazards, which then allows the community to take steps to reduce those hazards. As the Climate Assessment report notes, “disasters may result either from single, major events or from recurrent events that individually are not extreme, but degrade a community’s social and economic infrastructure.” 12

The climate action planning process for Salem included the important step of assessing Salem’s specific vulnerabilities to climate change. The process yielded valuable results which can inform the city’s approach to improving climate resilience.

Projected Temperature Increases for Oregon

Figure 3

Methodology

The methodology for completing the climate vulnerability assessment included the following steps:

1. OCCRI consultation

A consultation was conducted with Dr. Erica Fleishman, Director of the Oregon Climate Change Research Institute at Oregon State University. Dr. Fleishman recommended the online resource known as the Climate Toolbox as a source of climate projection data for Salem. She also recommended a vulnerability assessment framework developed by the Climate Impacts Research Consortium (CIRC).13

2. Climate projections

Climate projection data for the location of Salem, Oregon was obtained using the “Future Climate Dashboard” tool from the Climate Toolbox.13 Data was collected in the categories of heat indices, summer temperatures, winter temperatures, water, growing season, chilling hours, and fire danger. Additional sources were consulted to gain a full profile of Salem’s future climate.

3. Climate impacts

A Vulnerability Assessment Table was created based on the framework developed by CIRC. Climate impacts were grouped into four categories: warming temperatures, changes in precipitation patterns, increased fire risk, and reduced chilling hours.

4. Community impacts

The ways in which each climate projection data point could impact the Salem community was summarized in narrative form.

5. Likelihood

The likelihood of each climate impact occurring was rated according to the level of evidence.

6. Stressors and consequences

Next, projected intersections between non-climate and climate stressors were assessed. Non-climate stressors contain multiple impacts to the community that are not related to climate, and the examples assessed for Salem were population changes, increased demand for affordable housing, vulnerable populations, emerging health trends, local economy, and earthquake. Each of these non-climate stressors was examined in terms of how it might intersect with the identified climate stressors related to warming temperatures, changes to precipitation patterns, increased fire risk, and reduced chilling hours. From this assessment a consequence level between “negligible” and “catastrophic” was determined.

7. Risk

Using the determined values for likelihood and consequence level, a risk value from “low” to “extreme” was determined.

8. Adaptive capacity

Next, Salem’s adaptive capacity was rated. This assessment involved understanding where capacities exist in a community, where weaknesses exist, and how well the community is poised to respond to change from multiple stressors and impacts. To obtain information about Salem’s adaptive capacity, a meeting was held with City staff members on the project Advisory Committee. They were asked to respond to a survey in which they rated Salem’s adaptive capacity to respond to warming temperatures, changes in precipitation patterns and increased fire risk in the areas of social potential, organization capacity, and management potential. Their scores were analyzed and then used to assign an adaptive capacity rating of “low,” “medium,” or “high.”

9. Vulnerability

Finally, using the determined values for risk and adaptive capacity, a vulnerability level between “low,” “moderate,” and “high” was assigned for each climate impact area.

Projected Climate Impacts

Salem’s projected climate impacts will fall into three main categories: warming temperatures, changes in precipitation patterns, and increased risk of wildfire. A fourth impact, reduced number of chilling hours, is primarily pertinent to the agricultural sector.

Warming Temperatures

Salem’s average annual temperatures are expected to increase in the coming decades, with the most notable changes occurring in summer and winter. All projections assume a high-emissions scenario based on Representative Concentration Pathway 8.5 and use the 1990s average compared to projections by mid-century.15 The reason mid-century (year 2050) is used for projections rather than end-of-century (year 2100) is to align with the mid-century emissions reduction goal of this Climate Action Plan.

Projected Extreme Heat Days Per Year

Figure 4: Extreme heat days (days over 90°F) are projected to increase from a historic average of 7 per year to 33 per year by mid-century. Average days over 100°F will increase from 1 to 6.

The average summer temperature increase will be mild: it is projected to increase from a historic average of 66°F to 71°F by mid-century, while the average high summer temperature will increase from a historic average of 79°F to 86°F by mid-century.

What is of more concern is the projected increase in the number of extreme heat days, meaning days where the temperature exceeds 90°F. These temperatures can have serious health consequences such as heat exhaustion, heat cramps, mild heat edema (swelling in the legs and hands), heat syncope (fainting), and heat stroke.16 Salem’s increasing hot days will bring an increased risk of heat-related illnesses for small children, the elderly, people with chronic diseases, residents living at or near the poverty line, people who are unsheltered, and people who work outdoors. People who live in urban areas with little to no tree canopy are at risk of experiencing urban heat islands, areas where heat intensifies due to the absorption and re-emitting of the sun’s heat by buildings and roads. The Oregon Health Authority’s Climate and Health Profile Report identifies the urban heat island effect as the reason why residents of low-income urban neighborhoods are at greater risk of health-related illness and death from extreme heat.17 More extreme heat conditions may also bring an increase in respiratory problems, because higher temperatures contribute to the build-up in the air of harmful air pollutants.18

Winter temperatures, already mild in Salem, will become slightly warmer. The average high winter temperature is projected to increase from a historic average of 48.2°F to 52.5°F by mid-century. The coldest winter temperatures won’t be quite so cold in the future—the average winter low is projected to increase from a historic average of 34.6°F to 39°F by mid-century. Heating needs may decline and put slightly less demands on the energy system, but this could be offset by air conditioning energy demands on hot days.

Projected Winter Temperatures


Figure 5: The average high winter temperature is projected to increase from a historic average of 48.2°F to 52.5°F by mid-century.


Warming temperatures will lengthen Salem’s growing season, which may bring advantages to agricultural producers in the region. By mid-century, the growing season is expected to lengthen by 68 days, stretching from February to December. By the end of the century, the growing season will last nearly the entire year. While this shift may allow more varieties of crops to be grown in the area, any gains may be offset by other climate impacts like drought, wildfire, increased pests and diseases, and the shift away from traditional cold-season dependent crops.

Projected Growing Season


Figure 6: The growing season is expected to lengthen from a historic average of 227 days to 295 days by mid-century. By the end of the century, the growing season will last for nearly the entire year.



Potential Consequences

While Salem’s projected temperature increases will be mild, some consequences may be of concern:

  • Increased risk of heat-related illnesses to small children, the elderly, people with chronic illnesses, residents living at or near the poverty line, and people who work outside (e.g., farmworkers and construction workers), and people who are unsheltered.
  • Increased risk of respiratory problems.
  • Salem’s population is expected to grow 28% by 2035.19 Combined with warming temperatures, increases in population mean more people will likely use air conditioning on the warmest days, which may lead to an increased demand for electricity.
  • Warming temperatures will also likely lead to sustained or increased frequency of cyanotoxins, or harmful algal blooms, in the freshwater systems surrounding Salem. Exposure to cyanotoxins can cause hay fever-like symptoms, skin rashes, respiratory and gastrointestinal distress, and drinking untreated water containing cyanotoxins can cause liver and kidney damage.20) Salem has been monitoring and treating drinking water for cyanotoxins for years, and recently invested in a new ozone filtration system at the Geren Island water treatment plant to ensure drinking water for residents will continue to be safe. But recreational activities in local lakes and rivers could be inhibited.
  • Warming temperatures may allow for new pests to infiltrate the area New pests may have the ability to negatively impact Salem’s ecosystems, for example by harming the city’s tree canopy and spreading disease.
  • Decreased water levels in the reservoirs on the North Santiam River which provide all of Salem's water.

In summary, while higher summer temperatures may lead to health impacts for vulnerable populations, the temperature increase is not projected to be extreme and may be offset by people’s ability to naturally acclimate to changing temperatures over time. The issue of increasing cyanotoxins in drinking water due to algal blooms would be a significant risk to Salem’s residents if not for the important water treatment efforts already underway. In the vulnerability assessment (see Appendix 4), the overall risk level from warming temperatures was categorized as moderate. Salem’s assessed adaptive capacity, or ability to address these changes, was rated as moderate, which led to an overall vulnerability rating as moderate as well.

Projected Summer Temperatures


Figure 7: The average high summer temperature is projected to increase from a historic average of 79.3°F to 85.6°F by mid-century.


Changes in Precipitation Patterns

Overall precipitation in Salem is not projected to change significantly—an increase of only one inch per year is projected. However, because of warming temperatures, the type and timing of precipitation is likely to shift. One change will be a shift from mountain snow to rain in winter due to warming temperatures. Another change is a likely increase in unpredictable cloudburst events, in which an extreme amount of precipitation falls in a short amount of time. These events could lead to flash flooding in areas not designated as high risk.21) According to Dr. Erica Fleishman, Director of the Oregon Climate Change Research Institute, events where rain falls on existing snow accumulation (rain-on-snow events) have been increasing in Oregon, and can cause unexpected flooding due to runoff. Peak streamflows in the Willamette River are expected to increase from a historic average of 48,863 cfs (cubic feet per second) to 54,982 cfs by mid-century, meaning increased risk of flooding is possible.

While there will be more water flowing in some areas, other waterways will have less water. Salem’s water balance (the amount of annual rainfall minus the annual potential evapotranspiration) is projected to decrease from a historical surplus of three inches per year to a deficit of nearly one inch per year by mid-century, due to increasing evapotranspiration rates. A water deficit occurs when the amount of precipitation that falls in a specific period is exceeded by the amount of evapotranspiration that occurs during the same time period.22

U.S. Drought Monitor-Oregon


Figure 8: Oregon drought map as of September 7, 2021.

Drought is an important risk for the Salem area. The Fourth National Climate Assessment states that in Pacific Northwest, “periods of prolonged drought are projected to be interspersed with years featuring heavy rainfall driven by powerful atmospheric rivers and strong El Nino winters.” 23 In recent years, Oregon has experienced many of the associated impacts of drought, including stress to crops and livestock, reduced agricultural yields, reduced snowpack and runoff, reduced winter and summer recreation activities, fish die-offs, drinking water quality concerns, hydropower shortages, and larger wildfires. These impacts are expected to continue as climate change worsens.

Potential Consequences

The consequences from changing precipitation patterns could include the following:

  • Flood conditions could be exacerbated in areas outside the historical high-risk floodplain and where new development is occurring. Risks to unsheltered people living near waterways could increase.
  • Risk of water damage to homes and businesses from flooding.
  • Water intrusion in homes can create mold issues, respiratory issues, and psychological stress.
  • Potential harm to railroads, bridges, and overpasses from flooding.
  • Increased risk of drought, especially when combined with warmer temperatures.
  • Water use restrictions and food insecurity in periods of drought.


Water level at the Detroit Reservoir on the North Santiam River, 2021.


In summary, though overall precipitation amounts are expected to remain consistent, hotter temperatures will lead to a water deficit which may impact water supply and demand. Precipitation patterns may change, leading to increased frequency of heavy downpour events and flooding. Because Salem has had extensive experience dealing with flood events throughout its entire history as a city, the community’s adaptive capacity is relatively high when it comes to mitigating flood risk and recovering from flood events. Therefore, the overall vulnerability rating from changing precipitation patterns was rated as low in the vulnerability assessment.

Increased Risk of Wildfire

Wildfire is a significant increasing risk across the state, and the 2020 fire season presented historic events. According to the Fifth Oregon Climate Assessment report, “The total area burned in Oregon during summer and autumn 2020 was among the largest in recorded history. During the 2020 fire season, five wildfires over 100,000 acres, ignited by lightning and human activity, burned in wildlands and the wildland-urban interface. These and other fires across the western United States led to the displacement of thousands of people and loss of structures and infrastructure, and contributed to hazardous air quality in many parts of Oregon and the Northwest.” 24

Projected Wildfire Risk


Figure 9: The number of extreme fire danger days will double by mid-century


By the year 2100, annual area of land burned in the state, burn severity and frequency of wildfires are all projected to increase. One study estimated that the annual area burned in the Willamette Valley is projected to increase 900% by the end of the century, relative to the 1986-2010 average.25 A recent analysis of the impact of climate change on wildfire hazard in the nearby Clackamas Basin found that “all climate and baseline scenarios illustrate that extremely large, intense fires are plausible, and that they will become more plausible under hotter and drier climate scenarios.”26

The number of extreme fire danger days*27 in Salem will double by mid-century, increasing from a historic average of 10 per year to 20 per year. A majority of the increase will occur during the summer months.

With increased risk of fire comes the increased risks of fire damage to public and private properties, smoke inhalation, evacuation of residents, economic losses, landslides, erosion, water quality degradation, and transportation disruption. Unhealthy and hazardous air quality related to wildfire smoke can also take a physical and mental health toll on residents. Wildfire smoke contains a variety of gases and particles, including ozone, carbon monoxide, polycyclic aromatic compounds, nitrogen dioxide, and particulate matter—pollutants linked to respiratory and cardiovascular illnesses.28 What’s more, wildfires release great amounts of carbon dioxide, which works against local efforts to reduce GHG emissions.

Additional risks occur after a fire, including increased risk of landslides, potential negative environmental impacts from firefighting materials on soil and water resources, and degraded quality of surface water and drinking water due to post-fire debris, hazardous materials and soil movement.

Potential Consequences

  • The consequences from increasing wildfire risk could include the following:
  • Poor to hazardous air quality resulting from wildfires would greatly impact vulnerable populations—for example, people who are unsheltered, people who work outdoors, and people who live with chronic medical conditions such as asthma.
  • Salem’s drinking water source, the North Santiam River, could be degraded. Debris and chemicals in surface water following a fire could put additional pressure on water treatment facilities. The Geren Island water treatment plant could itself be at risk of wildfire.
  • Oregon’s population growth could lead to increased pressure to build housing in fire-prone zones, further exacerbating fire risk.
  • Higher than expected population growth. If people choose to relocate from other areas with higher climate change risk, the population influx could strain existing resources, services, and contribute to housing-related issues.
  • Fire-damaged forests and trails and poor air quality may reduce tourism and outdoor events in the area, resulting in economic impacts.


Wildfire smoke at Fairview Park, 2020


In summary, hotter and drier conditions will lead to increased fire risk in forested areas outside of Salem. Main impacts to Salem include health risks due to poor air quality, increased emergency operations and evacuations, and reductions in revenue and employment in the tourism industry. Salem could also experience higher than expected population growth as people from more climate change affected locations relocate due to their own fire risk. In the vulnerability assessment, the consequences from fire risk were rated as moderate and the risk high. However, Salem’s adaptive capacity was rated moderate, which led to an overall vulnerability rating of moderate.

* Extreme fire danger days are defined as the mean number of days in summer which are classified as very high fire danger days, calculated as the days with 100-hour fuel moisture that is below the 3rd percentile from historical years.

Reduced Number of Chilling Hours

“Chilling hours” generally refers to the number of hours between 32° and 45° that fruit and nut trees need to produce fruit successfully.29 Climate projections show that the number of chilling hours in Salem will decline from a historic annual average of 2,408 hours to 1,553 hours by mid-century. This reduction could have implications for fruit and nut tree growers in the Willamette Valley, but should not affect Salem residents directly. The risk level was rated as negligible in the vulnerability assessment.

Compounded Risk of Climate Impacts and Earthquake

According to the Marion County Emergency Operations Plan, a major earthquake is the highest-ranked risk to the area. There is approximately a 40% chance of an earthquake occurring along the Cascadia Subduction Zone in the next 50 years.30 Depending on the earthquake’s magnitude, critical infrastructure systems could be disrupted, including severe damage to energy, water, transportation, and communication systems.

If a major earthquake were to occur during an extreme weather event such as a wildfire or flood, the compounded effects could be catastrophic. Furthermore, earthquakes have the potential to cause wildfires (e.g., breaks in natural gas lines and downed power lines). With fire seasons projected to lengthen and extreme fire danger days to multiply, the risk of an earthquake occurring during fire season grows. Such overlapping events could lead to catastrophic consequences for the Salem area.

Conclusion

Whether it be extreme heat, prolonged drought, wildfires, dangerous air pollution from wildfire smoke, or ice storms, Salem residents are already feeling the effects of the changing climate.

These impacts will continue and may become exacerbated as the climate continues to change. Increased heat leads to reduced snowpack, reduced streamflow runoff, increased evapotranspiration, wildfire, drought, increased water use and risks to water quality. Increasing wildfire events and their associated impacts are the most serious projected climate risks for the Salem area.

Caution will need to be taken during extreme heat days in summer to protect vulnerable residents from heat stroke. The risk of flooding from unpredictable cloudburst events, or from rain-on-snow events, may cause problems for neighborhoods already at risk of flooding.

Food security for Salem residents may be impacted as local agricultural producers experience climate impacts or as regional transportation and supply chain networks may be disrupted by extreme weather events.

Having a clear understanding of these future climate risks will allow the Salem community to adequately prepare for a climate-altered future.

The state of Oregon is on pace to see temperatures rise by an average of 5°F by mid-century and by an average of 8.2°F by the 2080s.

Salem is fortunate to have a mild climate—only 21 degrees separate the average annual maximum temperature of 63.1ºF from the average annual minimum temperature of 42.1ºF.10 While this mild baseline means that the changes to Salem’s temperatures due to climate change may be less extreme than other locations in the country, the City will nevertheless experience notable shifts in the future.

Climate change is already affecting Oregon. The Fifth Oregon Climate Assessment describes increasing temperatures, changes to precipitation patterns, increased risk of floods, and increasing risk of wildfire across the state.11 Since 1895, Oregon has already experienced an average temperature increase of 2.2°F per century. The state is on pace to see temperatures rise by an average of 5°F by mid-century and by an average of 8.2°F by the 2080s. Summer temperatures are projected to increase the most. Rising temperatures, combined with changes in precipitation patterns, may lead to hotter and drier conditions that increase the risk of wildfires across the state and in the Salem area.

How Climate Risk is Created

Figure 2. Source. IPCC, 2014: Summary for policymakers. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, et. al. Mastrandrea, et. al., (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1-32.


A critical step of the climate planning process is to take a close look at the specific ways that Salem will be affected by projected climate change impacts. This process helps to identify potential hazards, which then allows the community to take steps to reduce those hazards. As the Climate Assessment report notes, “disasters may result either from single, major events or from recurrent events that individually are not extreme, but degrade a community’s social and economic infrastructure.” 12

The climate action planning process for Salem included the important step of assessing Salem’s specific vulnerabilities to climate change. The process yielded valuable results which can inform the city’s approach to improving climate resilience.

Projected Temperature Increases for Oregon

Figure 3

Methodology

The methodology for completing the climate vulnerability assessment included the following steps:

1. OCCRI consultation

A consultation was conducted with Dr. Erica Fleishman, Director of the Oregon Climate Change Research Institute at Oregon State University. Dr. Fleishman recommended the online resource known as the Climate Toolbox as a source of climate projection data for Salem. She also recommended a vulnerability assessment framework developed by the Climate Impacts Research Consortium (CIRC).13

2. Climate projections

Climate projection data for the location of Salem, Oregon was obtained using the “Future Climate Dashboard” tool from the Climate Toolbox.13 Data was collected in the categories of heat indices, summer temperatures, winter temperatures, water, growing season, chilling hours, and fire danger. Additional sources were consulted to gain a full profile of Salem’s future climate.

3. Climate impacts

A Vulnerability Assessment Table was created based on the framework developed by CIRC. Climate impacts were grouped into four categories: warming temperatures, changes in precipitation patterns, increased fire risk, and reduced chilling hours.

4. Community impacts

The ways in which each climate projection data point could impact the Salem community was summarized in narrative form.

5. Likelihood

The likelihood of each climate impact occurring was rated according to the level of evidence.

6. Stressors and consequences

Next, projected intersections between non-climate and climate stressors were assessed. Non-climate stressors contain multiple impacts to the community that are not related to climate, and the examples assessed for Salem were population changes, increased demand for affordable housing, vulnerable populations, emerging health trends, local economy, and earthquake. Each of these non-climate stressors was examined in terms of how it might intersect with the identified climate stressors related to warming temperatures, changes to precipitation patterns, increased fire risk, and reduced chilling hours. From this assessment a consequence level between “negligible” and “catastrophic” was determined.

7. Risk

Using the determined values for likelihood and consequence level, a risk value from “low” to “extreme” was determined.

8. Adaptive capacity

Next, Salem’s adaptive capacity was rated. This assessment involved understanding where capacities exist in a community, where weaknesses exist, and how well the community is poised to respond to change from multiple stressors and impacts. To obtain information about Salem’s adaptive capacity, a meeting was held with City staff members on the project Advisory Committee. They were asked to respond to a survey in which they rated Salem’s adaptive capacity to respond to warming temperatures, changes in precipitation patterns and increased fire risk in the areas of social potential, organization capacity, and management potential. Their scores were analyzed and then used to assign an adaptive capacity rating of “low,” “medium,” or “high.”

9. Vulnerability

Finally, using the determined values for risk and adaptive capacity, a vulnerability level between “low,” “moderate,” and “high” was assigned for each climate impact area.

Projected Climate Impacts

Salem’s projected climate impacts will fall into three main categories: warming temperatures, changes in precipitation patterns, and increased risk of wildfire. A fourth impact, reduced number of chilling hours, is primarily pertinent to the agricultural sector.

Warming Temperatures

Salem’s average annual temperatures are expected to increase in the coming decades, with the most notable changes occurring in summer and winter. All projections assume a high-emissions scenario based on Representative Concentration Pathway 8.5 and use the 1990s average compared to projections by mid-century.15 The reason mid-century (year 2050) is used for projections rather than end-of-century (year 2100) is to align with the mid-century emissions reduction goal of this Climate Action Plan.

Projected Extreme Heat Days Per Year

Figure 4: Extreme heat days (days over 90°F) are projected to increase from a historic average of 7 per year to 33 per year by mid-century. Average days over 100°F will increase from 1 to 6.

The average summer temperature increase will be mild: it is projected to increase from a historic average of 66°F to 71°F by mid-century, while the average high summer temperature will increase from a historic average of 79°F to 86°F by mid-century.

What is of more concern is the projected increase in the number of extreme heat days, meaning days where the temperature exceeds 90°F. These temperatures can have serious health consequences such as heat exhaustion, heat cramps, mild heat edema (swelling in the legs and hands), heat syncope (fainting), and heat stroke.16 Salem’s increasing hot days will bring an increased risk of heat-related illnesses for small children, the elderly, people with chronic diseases, residents living at or near the poverty line, people who are unsheltered, and people who work outdoors. People who live in urban areas with little to no tree canopy are at risk of experiencing urban heat islands, areas where heat intensifies due to the absorption and re-emitting of the sun’s heat by buildings and roads. The Oregon Health Authority’s Climate and Health Profile Report identifies the urban heat island effect as the reason why residents of low-income urban neighborhoods are at greater risk of health-related illness and death from extreme heat.17 More extreme heat conditions may also bring an increase in respiratory problems, because higher temperatures contribute to the build-up in the air of harmful air pollutants.18

Winter temperatures, already mild in Salem, will become slightly warmer. The average high winter temperature is projected to increase from a historic average of 48.2°F to 52.5°F by mid-century. The coldest winter temperatures won’t be quite so cold in the future—the average winter low is projected to increase from a historic average of 34.6°F to 39°F by mid-century. Heating needs may decline and put slightly less demands on the energy system, but this could be offset by air conditioning energy demands on hot days.

Projected Winter Temperatures


Figure 5: The average high winter temperature is projected to increase from a historic average of 48.2°F to 52.5°F by mid-century.


Warming temperatures will lengthen Salem’s growing season, which may bring advantages to agricultural producers in the region. By mid-century, the growing season is expected to lengthen by 68 days, stretching from February to December. By the end of the century, the growing season will last nearly the entire year. While this shift may allow more varieties of crops to be grown in the area, any gains may be offset by other climate impacts like drought, wildfire, increased pests and diseases, and the shift away from traditional cold-season dependent crops.

Projected Growing Season


Figure 6: The growing season is expected to lengthen from a historic average of 227 days to 295 days by mid-century. By the end of the century, the growing season will last for nearly the entire year.



Potential Consequences

While Salem’s projected temperature increases will be mild, some consequences may be of concern:

  • Increased risk of heat-related illnesses to small children, the elderly, people with chronic illnesses, residents living at or near the poverty line, and people who work outside (e.g., farmworkers and construction workers), and people who are unsheltered.
  • Increased risk of respiratory problems.
  • Salem’s population is expected to grow 28% by 2035.19 Combined with warming temperatures, increases in population mean more people will likely use air conditioning on the warmest days, which may lead to an increased demand for electricity.
  • Warming temperatures will also likely lead to sustained or increased frequency of cyanotoxins, or harmful algal blooms, in the freshwater systems surrounding Salem. Exposure to cyanotoxins can cause hay fever-like symptoms, skin rashes, respiratory and gastrointestinal distress, and drinking untreated water containing cyanotoxins can cause liver and kidney damage.20) Salem has been monitoring and treating drinking water for cyanotoxins for years, and recently invested in a new ozone filtration system at the Geren Island water treatment plant to ensure drinking water for residents will continue to be safe. But recreational activities in local lakes and rivers could be inhibited.
  • Warming temperatures may allow for new pests to infiltrate the area New pests may have the ability to negatively impact Salem’s ecosystems, for example by harming the city’s tree canopy and spreading disease.
  • Decreased water levels in the reservoirs on the North Santiam River which provide all of Salem's water.

In summary, while higher summer temperatures may lead to health impacts for vulnerable populations, the temperature increase is not projected to be extreme and may be offset by people’s ability to naturally acclimate to changing temperatures over time. The issue of increasing cyanotoxins in drinking water due to algal blooms would be a significant risk to Salem’s residents if not for the important water treatment efforts already underway. In the vulnerability assessment (see Appendix 4), the overall risk level from warming temperatures was categorized as moderate. Salem’s assessed adaptive capacity, or ability to address these changes, was rated as moderate, which led to an overall vulnerability rating as moderate as well.

Projected Summer Temperatures


Figure 7: The average high summer temperature is projected to increase from a historic average of 79.3°F to 85.6°F by mid-century.


Changes in Precipitation Patterns

Overall precipitation in Salem is not projected to change significantly—an increase of only one inch per year is projected. However, because of warming temperatures, the type and timing of precipitation is likely to shift. One change will be a shift from mountain snow to rain in winter due to warming temperatures. Another change is a likely increase in unpredictable cloudburst events, in which an extreme amount of precipitation falls in a short amount of time. These events could lead to flash flooding in areas not designated as high risk.21) According to Dr. Erica Fleishman, Director of the Oregon Climate Change Research Institute, events where rain falls on existing snow accumulation (rain-on-snow events) have been increasing in Oregon, and can cause unexpected flooding due to runoff. Peak streamflows in the Willamette River are expected to increase from a historic average of 48,863 cfs (cubic feet per second) to 54,982 cfs by mid-century, meaning increased risk of flooding is possible.

While there will be more water flowing in some areas, other waterways will have less water. Salem’s water balance (the amount of annual rainfall minus the annual potential evapotranspiration) is projected to decrease from a historical surplus of three inches per year to a deficit of nearly one inch per year by mid-century, due to increasing evapotranspiration rates. A water deficit occurs when the amount of precipitation that falls in a specific period is exceeded by the amount of evapotranspiration that occurs during the same time period.22

U.S. Drought Monitor-Oregon


Figure 8: Oregon drought map as of September 7, 2021.

Drought is an important risk for the Salem area. The Fourth National Climate Assessment states that in Pacific Northwest, “periods of prolonged drought are projected to be interspersed with years featuring heavy rainfall driven by powerful atmospheric rivers and strong El Nino winters.” 23 In recent years, Oregon has experienced many of the associated impacts of drought, including stress to crops and livestock, reduced agricultural yields, reduced snowpack and runoff, reduced winter and summer recreation activities, fish die-offs, drinking water quality concerns, hydropower shortages, and larger wildfires. These impacts are expected to continue as climate change worsens.

Potential Consequences

The consequences from changing precipitation patterns could include the following:

  • Flood conditions could be exacerbated in areas outside the historical high-risk floodplain and where new development is occurring. Risks to unsheltered people living near waterways could increase.
  • Risk of water damage to homes and businesses from flooding.
  • Water intrusion in homes can create mold issues, respiratory issues, and psychological stress.
  • Potential harm to railroads, bridges, and overpasses from flooding.
  • Increased risk of drought, especially when combined with warmer temperatures.
  • Water use restrictions and food insecurity in periods of drought.


Water level at the Detroit Reservoir on the North Santiam River, 2021.


In summary, though overall precipitation amounts are expected to remain consistent, hotter temperatures will lead to a water deficit which may impact water supply and demand. Precipitation patterns may change, leading to increased frequency of heavy downpour events and flooding. Because Salem has had extensive experience dealing with flood events throughout its entire history as a city, the community’s adaptive capacity is relatively high when it comes to mitigating flood risk and recovering from flood events. Therefore, the overall vulnerability rating from changing precipitation patterns was rated as low in the vulnerability assessment.

Increased Risk of Wildfire

Wildfire is a significant increasing risk across the state, and the 2020 fire season presented historic events. According to the Fifth Oregon Climate Assessment report, “The total area burned in Oregon during summer and autumn 2020 was among the largest in recorded history. During the 2020 fire season, five wildfires over 100,000 acres, ignited by lightning and human activity, burned in wildlands and the wildland-urban interface. These and other fires across the western United States led to the displacement of thousands of people and loss of structures and infrastructure, and contributed to hazardous air quality in many parts of Oregon and the Northwest.” 24

Projected Wildfire Risk


Figure 9: The number of extreme fire danger days will double by mid-century


By the year 2100, annual area of land burned in the state, burn severity and frequency of wildfires are all projected to increase. One study estimated that the annual area burned in the Willamette Valley is projected to increase 900% by the end of the century, relative to the 1986-2010 average.25 A recent analysis of the impact of climate change on wildfire hazard in the nearby Clackamas Basin found that “all climate and baseline scenarios illustrate that extremely large, intense fires are plausible, and that they will become more plausible under hotter and drier climate scenarios.”26

The number of extreme fire danger days*27 in Salem will double by mid-century, increasing from a historic average of 10 per year to 20 per year. A majority of the increase will occur during the summer months.

With increased risk of fire comes the increased risks of fire damage to public and private properties, smoke inhalation, evacuation of residents, economic losses, landslides, erosion, water quality degradation, and transportation disruption. Unhealthy and hazardous air quality related to wildfire smoke can also take a physical and mental health toll on residents. Wildfire smoke contains a variety of gases and particles, including ozone, carbon monoxide, polycyclic aromatic compounds, nitrogen dioxide, and particulate matter—pollutants linked to respiratory and cardiovascular illnesses.28 What’s more, wildfires release great amounts of carbon dioxide, which works against local efforts to reduce GHG emissions.

Additional risks occur after a fire, including increased risk of landslides, potential negative environmental impacts from firefighting materials on soil and water resources, and degraded quality of surface water and drinking water due to post-fire debris, hazardous materials and soil movement.

Potential Consequences

  • The consequences from increasing wildfire risk could include the following:
  • Poor to hazardous air quality resulting from wildfires would greatly impact vulnerable populations—for example, people who are unsheltered, people who work outdoors, and people who live with chronic medical conditions such as asthma.
  • Salem’s drinking water source, the North Santiam River, could be degraded. Debris and chemicals in surface water following a fire could put additional pressure on water treatment facilities. The Geren Island water treatment plant could itself be at risk of wildfire.
  • Oregon’s population growth could lead to increased pressure to build housing in fire-prone zones, further exacerbating fire risk.
  • Higher than expected population growth. If people choose to relocate from other areas with higher climate change risk, the population influx could strain existing resources, services, and contribute to housing-related issues.
  • Fire-damaged forests and trails and poor air quality may reduce tourism and outdoor events in the area, resulting in economic impacts.


Wildfire smoke at Fairview Park, 2020


In summary, hotter and drier conditions will lead to increased fire risk in forested areas outside of Salem. Main impacts to Salem include health risks due to poor air quality, increased emergency operations and evacuations, and reductions in revenue and employment in the tourism industry. Salem could also experience higher than expected population growth as people from more climate change affected locations relocate due to their own fire risk. In the vulnerability assessment, the consequences from fire risk were rated as moderate and the risk high. However, Salem’s adaptive capacity was rated moderate, which led to an overall vulnerability rating of moderate.

* Extreme fire danger days are defined as the mean number of days in summer which are classified as very high fire danger days, calculated as the days with 100-hour fuel moisture that is below the 3rd percentile from historical years.

Reduced Number of Chilling Hours

“Chilling hours” generally refers to the number of hours between 32° and 45° that fruit and nut trees need to produce fruit successfully.29 Climate projections show that the number of chilling hours in Salem will decline from a historic annual average of 2,408 hours to 1,553 hours by mid-century. This reduction could have implications for fruit and nut tree growers in the Willamette Valley, but should not affect Salem residents directly. The risk level was rated as negligible in the vulnerability assessment.

Compounded Risk of Climate Impacts and Earthquake

According to the Marion County Emergency Operations Plan, a major earthquake is the highest-ranked risk to the area. There is approximately a 40% chance of an earthquake occurring along the Cascadia Subduction Zone in the next 50 years.30 Depending on the earthquake’s magnitude, critical infrastructure systems could be disrupted, including severe damage to energy, water, transportation, and communication systems.

If a major earthquake were to occur during an extreme weather event such as a wildfire or flood, the compounded effects could be catastrophic. Furthermore, earthquakes have the potential to cause wildfires (e.g., breaks in natural gas lines and downed power lines). With fire seasons projected to lengthen and extreme fire danger days to multiply, the risk of an earthquake occurring during fire season grows. Such overlapping events could lead to catastrophic consequences for the Salem area.

Conclusion

Whether it be extreme heat, prolonged drought, wildfires, dangerous air pollution from wildfire smoke, or ice storms, Salem residents are already feeling the effects of the changing climate.

These impacts will continue and may become exacerbated as the climate continues to change. Increased heat leads to reduced snowpack, reduced streamflow runoff, increased evapotranspiration, wildfire, drought, increased water use and risks to water quality. Increasing wildfire events and their associated impacts are the most serious projected climate risks for the Salem area.

Caution will need to be taken during extreme heat days in summer to protect vulnerable residents from heat stroke. The risk of flooding from unpredictable cloudburst events, or from rain-on-snow events, may cause problems for neighborhoods already at risk of flooding.

Food security for Salem residents may be impacted as local agricultural producers experience climate impacts or as regional transportation and supply chain networks may be disrupted by extreme weather events.

Having a clear understanding of these future climate risks will allow the Salem community to adequately prepare for a climate-altered future.

The state of Oregon is on pace to see temperatures rise by an average of 5°F by mid-century and by an average of 8.2°F by the 2080s.

Page last updated: 15 November 2021, 15:09