Climate Primer
Missoula County, the City of Missoula, and Climate Smart Missoula developed a Climate Primer to inform stakeholders involved in the Climate Ready Missoula process. The Primer did not involve original research but drew on the wealth of information available on these topics, including the Montana Climate Assessment, the City and County Growth Policies, the Community Health Assessment, the Pre-Disaster Mitigation Plan, the Community Wildfire Protection Plan, and scientific papers.
The climate primer is divided into three sections: Missoula County Context, Climate Projections, and Scenarios. For more information on Missoula County context and the full text of our primer, you can delve into it here. The climate projection and scenario sections can be found below.
The climate primer is divided into three sections: Missoula County Context, Climate Projections, and Scenarios. For more information on Missoula County context and the full text of our primer, you can delve into it here. The climate projection and scenario sections can be found below.
Climate Projections
"In brief: Missoula County’s summers are expected to become hotter and drier. Winters and springs are expected to become warmer and wetter. More precipitation will fall as rain instead of snow, especially at low elevations. These changes will directly impact our quality of life and the local economy. " - Missoula Climate Primer, p. 14
Historically, temperatures have been rising.
100% of global climate models agree that they are projected to increase, both under a stabilization and business as usual scenario.
With the largest increase in temperature occurring in the summer months.
Precipitation is a little more complicated - historically, we have not had much of a change in precipitation.
But in the future, we are expecting an overall increase in annual precipitation.
Unfortunately, these annual cumulative increases are different than summer trends, when we need it most. We are expected to see a decrease in precipitation during the summer.
The timing of this rainfall is important, as it affects things like wildfire, drought, and heat stress on people and animals.
This is just one reason that this work on resiliency is so important. In this example, our overall resource (total precipitation) is not declining, but the timing is shifting.
Can we develop appropriate strategies to adapt to these projected changes?
Mid-Century Climate Scenarios for Missoula County
The three scenarios below describe plausible futures that Missoula County could face in the next 30 years based on current trends, recent events, scientific research, and climate projections (citations available upon request). This is not intended to be an exhaustive depiction of plausible impacts, but rather to provide detailed descriptions of what the future could look like in order to prepare for the range of futures that climate change might bring to Missoula County. Scenarios are used in climate adaptation planning to tangibly represent key uncertainties related to a) projected changes in temperature and precipitation at the local scale, and b) the implications of those changes for ecosystems and human communities. These scenarios were reviewed by seven subject matter experts to ensure that they reflect the latest science on current and projected climate impacts.
Scenario 1 | Turn Up the Heat
Overview
Fire and smoke.
With higher temperatures and less precipitation in the summer and early fall, fire seasons will last an average of 12 days longer than they do today, and the total land area burned each year will increase about 50% on average. While we will not see extensive, region-wide burning every year, fire seasons like 2012 and 2017, which saw widespread burning across the northern Rockies, will become more frequent. Wildfires will pose an increasing threat to the lives and properties of Missoula County residents, in particular those who reside in the wildland-urban interface (which encompasses nearly all inhabited areas of Missoula County, with the exception of the Missoula urban core). Over time, increases in the size and severity of fires will reduce the extent of low elevation forests, converting forested areas to shrublands or grasslands. Invasive species such as leafy spurge and spotted knapweed thrive in areas that have been recently disturbed and will increase their range as a result of more area burned. Warmer winters will also promote larger pine beetle populations. Longer and more intense fire seasons in Missoula County and throughout the region will mean longer periods of unhealthy air quality due to wildfire smoke, increasing the incidence and severity of respiratory and cardiovascular disease among county residents. Emergency room visits for breathing problems, heart attacks, and strokes will spike during periods of dense wildfire smoke. Children, the elderly, people with heart and lung disease, and outdoor workers will be among the most impacted. The smoke season will last well into September, and possibly October, with increasing impacts on schools and fall athletic programs. Outdoor recreation and tourism will decline during periods of wildfire smoke. Portions of Yellowstone and Glacier National Parks will close more frequently due to wildfires; and even when the parks are open, wildfire smoke will obscure vistas and deter tourists. Thousands of jobs will be lost in the tourism industry statewide. water.
Warmer winters will lead to a decline in mountain snowpack. That snowpack will melt earlier due to warmer spring temperatures, leading to peak streamflows 2-3 weeks earlier in the year. Late summer streamflows will be much lower than they are now, reducing the amount of water available for fish and riparian vegetation. In addition, lower flows combined with hotter summers will mean higher river temperatures, reducing populations of temperature-sensitive species such as bull trout. Higher river temperatures will lead to more frequent and longer-lasting “hoot owl” fishing restrictions, which prohibit fishing during certain hours of the day in order to minimize stress on trout when water temperatures are high. Warming water temperatures may also result in the proliferation of parasites, viruses, fungal infections, and algae blooms, impairing water quality, affecting aquatic plants, and killing fish. Due to a later fall freeze and earlier spring thaw, the growing season will increase in length by about 2 months. While annual precipitation does not change in this scenario, warmer temperatures will result in increased evaporation, reducing the water available for plant growth by 4-8%. In addition, less summer precipitation and lower August streamflows will mean that less water is available for agriculture during the growing season. The longer growing season could be beneficial to irrigated agricultural producers in the county, as long as they have adequate access to water for irrigation. Warmer temperatures might also benefit the nascent viticulture industry in Missoula County. However, some crops may be damaged by heat stress due to hotter summer temperatures, and ranchers will experience decreased forage production and an increase in invasive species on rangelands. Reduced snowpack and earlier snowmelt will impact winter recreation. For example, Snowbowl will face shorter ski seasons and more frequent closures of low-elevation terrain, and opportunities for low-elevation nordic skiing and backyard ice skating will be reduced or eliminated. Seasons for other recreational sports such as mountain biking may be extended due to warmer springs and falls, but will also be affected by wildfire smoke. |
Scenario 2 | Here Comes the Rain
Overview
changing seasons.
While summer precipitation does not change in this scenario, hotter summers increase evaporation rates, reducing water available for plant growth in the summer and resulting in a greater contrast between wet and dry seasons. Early but short spring rains promote rapid greenups, followed by prolonged dry summers and brown landscapes. The growing season increases in length by 2-3 weeks due to increased fall and spring temperatures. These conditions will expand not only the growing season, but also the types of crops we can grow in Missoula County, as well as affecting the timing of planting, fertilizer application, and harvest. Elk and other wildlife will benefit from the availability of ample forage in early spring, but may be forced to change their normal winter ranges due to warmer winters and deeper mountain snowpack. flooding.
Throughout Montana’s history, “rain on snow” events have caused the most severe and destructive floods. In this scenario, warmer temperatures and wetter winters and springs will cause more rain on snow events and faster snowmelt, leading to more frequent and severe flooding. By mid-century, the average winter and spring will be even warmer and wetter than 2018, when the Clark Fork River crested at its second highest level in 100 years and severe flooding damaged houses and tipped power poles. More frequent and severe flooding will lead to extensive property damage and pose a risk to the health and safety of the hundreds of Missoula County residents who live or work in the floodplain. Flooding will also increase the incidence of waterborne illness such as giardia. In the urban area, more severe rain events will challenge our stormwater system, and greater volumes of stormwater runoff that flow to the aquifer will increase the potential for contamination of our drinking water supply. Flooding will impact populations of fall spawning fishes, such as bull trout, whose eggs and young are vulnerable to spring floods. |
Scenario 3 | Feast or Famine
Overview
variability.
On average, the total area burned by wildfires each year will be larger than it is today but smaller than in Scenario 1 Turn Up the Heat. Increased year-to-year variability in precipitation will result in increased variability in fire season length and area burned. Intense rainfall will reduce total area burned in some years, depending on the timing within the fire season. The timing of season-ending events, in particular, will be highly variable among years. In dry years, we will experience low late-summer streamflows and reduced water available for plant growth, with impacts on aquatic ecosystems, river recreation, and agriculture similar to Scenario 1. In wet years we will experience flood events similar to those described in Scenario 2 Here Comes the Rain Again. Flooding will be exacerbated by the increase in wildfires in dry years, since rainfall runoff over burned areas can cause flash flooding. Burned hillsides are also vulnerable to landslides when it rains, resulting in soil loss which degrades land, slows regrowth, and leads to excessive sedimentation in streams and rivers. From year to year, the season and conditions for outdoor activities like skiing and fishing will vary dramatically. Businesses involved in outdoor recreation and those that cater to tourists will be particularly challenged to prepare for this unpredictability. Increased variability will also be difficult for farmers and ranchers in the county, as the strategies for drought years may be very different from wet years. Indeed, not being able to plan for an “average year” can be difficult for many, from athletes (youth to adult) to construction firms. Being forced to alter schedules and expectations each season can be stressful and economically costly. ecosystems.
Extreme conditions such as long winters with heavy snowfall and summer drought are hard on fish and wildlife. For example, elk distributions will change due to long winters in some years and dry summers in other years. Fish that spawn in the fall are vulnerable to spring flooding; and all fish species are stressed by low summer flows and warmer river temperatures. |