Conditions Update 2024

During a time when shocking new climate extremes are common, 2023 in Pitkin County was shockingly normal. The average temperature in the county was 36.9°F, matching the average temperature for the 20th century. Precipitation was 30.35 inches, which was 1.2 inches above the 20th century average of 29.15 inches. This is “shockingly normal” because 2008 was the last time the temperature was at or below average; in other words, 2023 and 2008 are the only two years since 2000 that the temperature in Pitkin County was not above average. But in many other areas around the world, the 2023 climate story was markedly different.

Globally, 2023 was the warmest year on record. High temperature records were set for individual months June through December. Notably, 2023 was also the first year that global temperatures surpassed the 1.5°C climate threshold, the aspirational benchmark for global average surface warming established by the 2015 Paris Climate Agreement (the goal is to stay less than 1.5°C above pre-industrial temperatures). Scientists were expecting a hot year—at the start of 2023, scientists predicted that the year would be between the ninth and third warmest on record, but temperatures greatly surpassed expectations.1 As of publication, scientists have yet to reach a definitive explanation as to the cause of the exceptional warmth. While the majority of the warming can be attributed to climate change, scientists believe that other factors, including increased solar radiation, El Niño, increased water vapor in the atmosphere from the Hunga Tonga-Hunga Ha’apai eruption in 2022 (the largest volcanic eruption to date in the 21st century), and the use of lower sulfur marine fuels all contributed to the record-setting temperatures. As El Niño shifts to La Niña, the impact of Hunga Tonga fades, and as we pass the peak of the solar cycle, slightly lower temperatures are possible.

In the Roaring Fork watershed, the Douglas-fir beetle, spruce beetle, and western spruce budworm are the most active forest pests. The activities of the Douglas-fir beetle and spruce beetle followed a similar trajectory in 2023 as in previous years. The Douglas-fir beetle continues to spread throughout the mid-elevations of our watershed, primarily between 7,000 and 9,000 feet in elevation. Spruce beetles, while largely absent from the Roaring Fork watershed, continue to be active in the northern areas of the Taylor River Basin to our south. Aerial surveys conducted during the late summer/early fall in 2023 showed potential spruce beetle activity in upper Difficult Creek, but we have yet to confirm these reports with on-the-ground observations. The mountains between the watersheds impede beetle flight, but under the right conditions a strong wind could transport a large number of beetles from the Taylor River Basin into Lincoln Creek.

In addition to the activity of Dendroctonus beetles (bark beetles), a significant western spruce budworm outbreak is ongoing in the Crystal River Basin. This is a part of a broader statewide outbreak that covered 202,000 acres in 2023, making it the most widespread forest pest in the state. Despite its name, the western spruce budworm affects more than spruce trees. In our valley, Douglas fir, subalpine fir, and Engelmann spruce trees are all potential hosts. Western spruce budworm has four life stages: egg, larva, pupa, and adult. The adults are moths that lay eggs on the undersides of conifer needles in the late summer. The eggs hatch after approximately 10 days and then overwinter under bark scales or lichen on the trunk of the tree. In the spring, the larva begins feeding on the new buds before pupating and starting the cycle again. An otherwise healthy tree can typically survive an outbreak of western spruce budworm. Unfortunately, many of the conifer trees in our forests aren’t healthy, as they have been stressed by years of drought and above-average temperatures. Paired with outbreaks of Dendroctonus beetles, we’re seeing increased mortality across the state from western spruce budworm.

No portion of Pitkin County was in a state of drought in 2023, for the first time in four years, according to the U.S. Drought Monitor. Since its inception in 2000, the U.S. Drought Monitor has shown a portion of Pitkin County in a state of drought 62 percent of the time, while the entire county has been in a state of drought 42 percent of the time. Drought is typically thought of as a lack of precipitation, but that is only part of the story. Drought is defined in different ways depending on who or what is being impacted. The National Weather Service defines drought as: “a deficiency of moisture that results in adverse impacts on people, animals, or vegetation over a sizable area.” This lack can be caused by a deficit of precipitation or by higher temperatures, resulting in an increase in evapotranspiration (a combination of evaporation from the ground or water bodies and transpiration or water loss from plants). As climate change continues to impact Colorado, increased temperatures are playing a larger role in our droughts, and we are seeing effects in our ecosystems and our water supply across the Colorado River Basin.

The last time the Colorado River reservoir system was at full capacity was in 1999. As of November 14, 2023, the reservoir system was 41 percent full. This is a marked improvement from the previous November, when the system was 31 percent full. That increase is thanks to the large amount of runoff produced in 2023; since 2000, only 2011 produced more runoff. The gains in storage in 2011 were gone by 2013 due to water loss from consumption and evaporation. In fact, gains in water stored from all five of the highest runoff years since 2000 were gone in two years or less. For reservoirs in the Colorado River system to reach capacity, we would need six additional large runoff years like 2023.2 While some of the lack of capacity can be attributed to decreases in precipitation, a significant portion of the declining water availability in the 21st century has been caused by higher temperatures.

As a result of anthropogenic warming, temperatures across the Colorado River Basin have increased an average of 1.5℃3 since the 1880s, which is when accurate recording began. Scientists estimate that for every 1℃ of temperature increase, the natural flow of water in the Colorado River declines by 6.8 percent.4 From 2000–21 the increase in atmospheric temperature caused a loss of approximately 40 trillion liters of water in the Colorado River Basin, which is about the water storage capacity of Lake Mead. In other words, without the temperature increases caused by climate change, the volume of water would currently be at full capacity. This sobering fact that climate change is behind the current state of drought and decreased water availability across the West is compounded by the reality that climate change is here to stay.

Wildfires are a vital component of forest ecosystems in Colorado and across the western United States, which is why decades of fire suppression have significantly degraded the health of many forests. Over time, the absence of fire indicates the ongoing suppression of a natural process. However, an increase in fire activity can indicate deteriorating forest health. A shift in species composition, often due to invasive species like cheatgrass, can escalate fire activity. And human-caused fires often reflect increased development or use of wild spaces. Additionally, rising wildfire occurrences may signal that the climate is becoming more conducive to fires. A warmer climate, driven by human-induced climate change, is expected to heighten fire activity.

Increased fire activity can also lead to yet more climate change. Globally, between 2001 and 2022, wildfires emitted 33.9 billion tonnes of carbon dioxide. If wildfires were a country, they would be the sixth largest emitter of greenhouse gasses.7 Historically, these emissions would be balanced out by forests growing and sequestering a similar amount of carbon dioxide. But with both climate change and human disruptions to natural fire cycles, we’re seeing larger areas of forests burning without the expected amount of regrowth.

In 2023, wildfires burned 2.4 million acres in the country, substantially below the 2001–20 average of over 6 million acres, making it the least extensive wildfire season in the U.S. since 1998. Colorado’s statistics closely align with these national figures, with the area burned in 2023 amounting to just over one-third of the average area burned between 2001 and 2020. In Colorado, this was a consequence of the near-average temperatures and precipitation (see Climate and Water updates).

While 2023 offered a much-needed respite after many years of significant wildfires and smoke impacts in Colorado, this trend is not expected to continue. Factors such as increased human presence in or near wild areas, a century of fire suppression, and an intensified fire cycle due to climate change are likely to continue amplifying wildfire activity in the western United States.

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