Climate change in Idaho

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Like other parts of the world, climate in Idaho has changed dramatically over the geologic history of the Earth. Paleo-climatic records give some indication of these changes. The longest instrumented records of climate in Idaho extend back to the late 1800s. Concern over human induced climate change through the emission of carbon dioxide from fossil fuels and methane from agriculture and industry, are driving research efforts across the state at university, state, and federals levels to understand what the implications of climate change could be in Idaho.

In the big picture of greenhouse gas emissions, Idaho emits the least carbon dioxide per person of the United States, less than 23,000 pounds a year. It relies mostly on nonpolluting hydroelectric power from its rivers.^[1][2]

Like other parts of the world, Idaho has seen significant temperature increases, especially in the last several decades. From 1971 to 2005 the average annual observed temperature in the Snake River Plain, located in southern Idaho, has increased by 1.4 degrees Celsius based on data from 10 climate stations (Dubois, Ashton, Oakely, Pocatello, Aberdeen, Hazelton, Jerome, Boise, Nampa, and Payette). Statistically the increasing temperature trends are most significant in the months of January, March, and April.^[3] While precipitation has generally increased since the early 1900s, the high variability in precipitation makes the identification of precipitation trends statistically difficult.

Over the course of the 21st century, climate in Idaho is expected to experience additional changes due both to 'natural' climate variability and due to feedbacks related to the interaction between climate variability and increasing greenhouse gases. For example, based on projections made by the Intergovernmental Panel on Climate Change and results from the United Kingdom Hadley Centre’s climate model (HadCM2), a model that accounts for both greenhouse gases and aerosols, by 2100 temperatures in Idaho could increase by 5 °F (2.8 °C) (with a range of 2 °F (1.1 °C) to 9 °F (5.0 °C)) in winter and summer and 4 °F (2.2 °C) (with a range of 2 °F (1.1 °C) to 7 °F (3.9 °C)) in spring and fall. Precipitation is estimated to change little in summer, to increase by 10% in spring and fall (with a range of 5-20%), and to increase by 20% in winter (with a range of 10-40%). Other climate models may show different results, especially regarding estimated changes in precipitation. The impacts described in the sections that follow take into account estimates from different models. The amount of precipitation on extreme wet or snowy days in winter is likely to increase. The frequency of extreme hot days in summer would increase because of the general warming trend. It is not clear how the severity of storms might be affected, although an increase in the frequency and intensity of winter storms is possible.