Climate change is impacting our environment

Globally, temperatures are rising, and temperature and precipitation extremes are becoming more common.1 In the United States, average annual temperatures increased by 1.8°F between 1895 and 2016.2 Human activities in the past 50 years, resulting in an unprecedented accumulation of greenhouse gases, especially carbon dioxide, methane, and nitrous oxide, are the primary cause of this warming.3 For example, atmospheric carbon dioxide has increased by more than 40% since the Industrial Revolution (which lasted from about 1760 to about 1840), primarily due to burning coal, oil, and gas, and forest clearing.4

Looking solely at global or national averages does not give an accurate picture of climate change impacts in north central Montana. Impacts in this area may be greater than national averages would suggest, because the rate and magnitude of climate warming in Montana has been greater. For example, the average annual temperature in Montana increased 2.7°F between 1950 and 2015,5 much higher than the amount of warming the United States has experienced over an even longer time period.

glacier_change
Figure 1: Photos of Grinnell Glacier in Glacier National Park show the Glacier has diminished considerably in size from 1887 to 2013.6

While such change can be difficult to visualize, the disappearing glaciers in Glacier National Park are a local, visible reminder that the climate is warming (Figure 1). Since 1966, 39 glaciers in the Park have shrunk, some by as much as 85%.7 Other climate change impacts may not be as easy to see at first glance, though the accumulating effects on the local environment, air, water, weather, oceans, and ecosystems are significant. This section highlights the major ways climate change is impacting the regional environments of north central Montana.

Zones with Blackfeet Nationa
Figure 2: Map of Montana Climate Divisions.  The Blackfeet Nation is located in the North Central Climate Division 3, a climate division defined by the National Ovceanic and Atmospheric Administration (Image Source: NOAA at http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_monitoring/CLIM_DIVS/montana.gif)

The Blackfeet Nation is located in Montana’s North Central region (Division 3), a climate division defined by the National Oceanic and Atmospheric Administration (Figure 2). The North Central region has seen an average temperature increase of .51°F each decade from 1950 to 2015, with most warming occurring in winter and spring (Figure 3).8 In the same period, total days exceeding 90°F in Montana has increased by 11 days while the percentage of cool days each year has decreased by 15 days.9 Though Montana’s overall growing season length has increased by 12 days,10 effective season length can be limited by reduced water availability.11 While the North Central region has not seen a significant change in summer, fall, and spring precipitation since 1950, it has had an average precipitation decrease of .09 inches per decade in winter, mostly attributed to natural climate variability.12 Furthermore, the Central Rocky Mountains have been experiencing declining stream discharge over the last half century, with significant declines in the month of August.13

temp_1950-2017
Figure 3: Data from the National Oceanic and Atmospheric Administration shows a trend of increasing average temperature (.5°F per decade) in North Central Montana since at least 1950.

To understand how climate change will impact north central Montana’s environment in the future, it is important to acknowledge several sources of uncertainty when making predictions at the regional scale. Climate modeling, ecological responses, and human adaptive responses all introduce uncertainty when predicting the future.14 While there is consensus that climate change is happening and that its impacts are here and will be experienced far into the future, the degree to which it will impact the globe depends on how people act now and in the future. While precise predictions cannot be made about future conditions, there is evidence that across Montana, average annual temperatures will increase (high agreement, robust evidence), annual precipitation will increase in winter, spring, and fall (moderate agreement, moderate evidence), and precipitation will decrease in the summer across Montana (moderate agreement, moderate evidence).15

Contributing to uncertainty is the degree to which the global community will take action to limit and reduce greenhouse gas emissions. When scientists make climate predictions, they must account for different emissions scenarios, which are referred to as Representative Concentration Pathways, or RCPs.  For example, RCP 2.6, at one extreme, assumes “immediate and rapid reductions in emissions,” while RCP 8.5, at the other extreme, assumes a continuation of current global emission increases.16 A more middle-of-the-road scenario is RCP 4.5, known as the stabilization scenario. The United Nations Paris Agreement intends to curb emissions at levels between RCP 2.6 and RCP 4.5.17 Table 1 compares North Central Montana scenarios for RCP 4.5 with RCP 8.5. Note that the overall trends are similar for the two scenarios: hotter average temperatures, longer growing seasons, increased late winter and early spring precipitation, and decreased summer precipitation). However, the magnitude of change is greater for RCP 8.5.

climate change table updated.png
Table 1: Mid-Century and End-of-Century Climate Change Predictions for the North Central Montana Climate Division.  Climate Change predictions are based on comparisons to historical 30-year averages from 1971 to 2000.  Source: 2017 Montana Climate Assessment18

In Montana, state-wide average annual temperature is expected to rise up to 6.6°F (for RCP 4.5) and possibly up to 10.8°F (for RCP 8.5) by the end of this century.19 Climate modeling experts predict there will be 3 – 7 more high temperature days per year by the mid-century in North Central Montana, based on the RCP 4.5 scenario.20 The hotter temperature days are predicted to increase most in the month of August,21 a time when water is in shortest supply. Monthly precipitation will decrease, on average, up to 5 inches in North Central Montana in the months of June, July, and August in the period 2040 to 2069 (for both RCP 4.5 and 8.5 scenarios).22 In contrast, monthly precipitation is expected to increase up to 7.5 inches in March, April, and May in North Central Montana the same period (RCP 4.5), and possibly greater increases are expected under the RCP 8.5 scenario.23 Warmer temperatures are likely to increase the frequency and severity of drought conditions in the late summer and early fall, and exacerbate drought conditions when they do occur throughout the year.24

CS_seasonal_precip_projections_RCP-NO_TITLE_V8
Figure 4: This figure, from the 2014 National Climate Assessment, shows the predicted precipitation change in each season under RCP 2.6 and RCP 8.5. Under both scenarios, precipitation is expected to increase in winter and spring in north central Montana, and either decrease (RCP 8.5) or remain the same (RCP 2.6) in summer. (Image source: NOAA NCDC/ CICS-NC).

Though summer precipitation will decline, winter and spring snowmelt and precipitation predictions suggest water availability may concentrate in the relatively cooler parts of the year.25,26 Decreased spring snowpack has been observed and is predicted into the future,27,28,29 as is an earlier onset of spring snowmelt.30,31,32 This means that peak spring stream runoff is occurring earlier in the year,33,34,35 and more runoff in winter is predicted.36 Furthermore, long-term stream monitoring has demonstrated that there are already lower stream baseflows (the portion of the stream not from runoff) in late summer,37,38,39 a trend predicted to continue into the future. These lower baseflows, along with warmer air temperatures, are causing stream temperatures to warm.40,41 The frequency of flooding may increase, especially in spring, due to earlier snowmelt, rain-on-snow events and increased precipitation.42,43

In short, climate change is likely to raise temperatures, increase precipitation and snowmelt in colder parts of the year, and decrease precipitation in hotter parts of the year in North Central Montana. These trends have a variety of implications for humans and the environment. A major implication is that rising temperatures and changes in snowpack and runoff timing will exacerbate drought.44 Living with climate change will require adaptation and increased resilience in Blackfeet Country.


Literature Cited

Halofsky, Jessica E., David L. Peterson, S. Karen Dante-Wood, Linh Hoange, Joanne J. Ho, and Linda A. Joyce. “Climate Change Vulnerability and Adaptation in the Northern Rocky Mountains.” Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, 2017.

Hamlet, A. F., and D. P. Lettenmaier. “Effects of 20th Century Warming and Climate Variability on Flood Risk in the Western U.S.”. Water Resources Research 43, no. 6 (2007).

Isaak, D., S. Wollrab, D. Horan, and G. Chandler. “Climate Change Effects on Stream and River Temperatures across the Northwest Us from 1980-2009 and Implications for Salmonid Fishes.” Climatic Change 113, no. 2 (2012): 499-524.

Leppi, J., T. DeLucal, S. Harrar, and S. Running. “Impacts of Climate Change on August Stream Discharge in the Central-Rocky Mountains.” Climatic Change 112, no. 3-4 (2012): 997-1014.

Luce, C. H., and Z. A. Holden. “Declining Annual Streamflow Distributions in the Pacific Northwest United States, 1948–2006.” Geophysical Research Letters 36, no. L16401 (2009).

Mantua, N., I. Tohver, and A. Hamlet. “Climate Change Impacts on Streamflow Extremes and Summertime Stream Temperature and Their Possible Consequences for Freshwater Salmon Habitat in Washington State.” Climatic Change 102, no. 1-2 (2010): 187-223.

McKeon, Lisa. “Grinnell Glacier 1887-2013.” U.S. Geological Survey, 2016. https://www.usgs.gov/centers/norock/science/grinnell-glacier-1887-2013?qt-science_center_objects=0#qt-science_center_objects

Melillo, Jerry M., Terese (T.C.) Richmond, and Gary W. Yohe. “Climate Change Impacts in the United States: The Third National Climate Assessment.” 2014.

Romero-Lankao, P., J.B. Smith, D.J. Davidson, N.S. Diffenbaugh, P.L. Kinney, P. Kirshen, P. Kovacs, and L. Villers Ruiz. “North America.” In Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, edited by V.R. Barros, C.B. Field, D.J. Dokken, M.D. Mastrandrea, K.J. Mach, T.E. Bilir, M. Chatterjee, et al. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press, 2014. http://www.ipcc.ch/pdf/assessment-report/ar5/wg2/WGIIAR5-Chap26_FINAL.pdf.

Rood, SB, J Pan, KM Gill, CG Franks, GM Samuelson, and A. Shepherd. “Declining Summer Flows of Rocky Mountain Rivers: Changing Seasonal Hydrology and Probable Impacts on Floodplain Forests.” Journal of Hydrology 349, no. 3-4 (2008): 397-410.

Soileau, Suzanna, Paul Lausten, and Ken Ma. “Glaciers Rapidly Shrinking and Disappearing: 50 Years of Glacier Change in Montana.” U.S. Geological Survey, 2017. https://www.usgs.gov/news/glaciers-rapidly-shrinking-and-disappearing-50-years-glacier-change-montana

Stewart, I. T., D. R. Cayan, and M. D. Dettinger. “Changes toward Earlier Streamflow Timing across Western North America.” Journal of Climate 18 (2005): 1136-55.

USGCRP. “Climate Science Special Report: A Sustained Assessment Activity of the U.S. Global Change Research Program.” edited by D.J. Wuebbles, D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock. Washington, DC., 2017.

Whitlock, C., W. Cross, B. Maxwell, N. Silverman, and A.A. Wade. “2017 Montana Climate Assessment.” Bozeman and Missoula, MT, 2017.


Footnotes

[1] USGCRP (2017), “Climate Science Special Report: A Sustained Assessment Activity of the U.S. Global Change Research Program”, U.S. Global Change Research Program.

[2] Jerry M. Melillo, Terese (T.C.) Richmond, and Gary W. Yohe (2014), “Climate Change Impacts in the United States: The Third National Climate Assessment”, U.S. Global Change Research Program.

[3] Ibid.

[4] USGCRP (2017), “Climate Science Special Report: A Sustained Assessment Activity of the U.S. Global Change Research Program”.

[5] C. Whitlock et al. (2017), “2017 Montana Climate Assessment”, Montana Institute on Ecosystems Montana State University and the University of Montana.

[6] Lisa McKeon (2016), “Grinnell Glacier 1887-2013,” U.S. Geological Survey, https://www.usgs.gov/centers/norock/science/grinnell-glacier-1887-2013?qt-science_center_objects=0#qt-science_center_objects.

[7] Suzanna Soileau, Paul Lausten, and Ken Ma (2017), “Glaciers Rapidly Shrinking and Disappearing: 50 Years of Glacier Change in Montana,” U.S. Geological Survey, https://www.usgs.gov/news/glaciers-rapidly-shrinking-and-disappearing-50-years-glacier-change-montana

[8] Whitlock et al. (2017), “2017 Montana Climate Assessment”.

[9] Ibid.

[10] Ibid.

[11] Jessica E. Halofsky et al. (2017), “Climate Change Vulnerability and Adaptation in the Northern Rocky Mountains”, Forest Service U.S. Department of Agriculture, Rocky Mountain Research Station.

[12] Whitlock et al. (2017), “2017 Montana Climate Assessment”.

[13] J. Leppi et al. (2012), “Impacts of Climate Change on August Stream Discharge in the Central-Rocky Mountains,” Climatic Change 112, no. 3-4.

[14] Whitlock et al. (2017), “2017 Montana Climate Assessment”.

[15] Ibid.

[16] Halofsky et al. (2017), “Climate Change Vulnerability and Adaptation in the Northern Rocky Mountains”.

[17] Whitlock et al. (2017), “2017 Montana Climate Assessment”.

[18] Ibid.

[19] Ibid.

[20] Ibid.

[21] Ibid.

[22] Ibid.

[23] Ibid.

[24] Ibid.

[25] Ibid.

[26] Melillo, Richmond, and Yohe (2014), “Climate Change Impacts in the United States: The Third National Climate Assessment”.

[27] Whitlock et al. (2017), “2017 Montana Climate Assessment”.

[28] A. F. Hamlet and D. P. Lettenmaier (2007), “Effects of 20th Century Warming and Climate Variability on Flood Risk in the Western U.S.,” Water Resources Research 43, no. 6.

[29] P. Romero-Lankao et al. (2014), “North America,” ed. V.R. Barros, et al., Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press),  http://www.ipcc.ch/pdf/assessment-report/ar5/wg2/WGIIAR5-Chap26_FINAL.pdf.

[30] Whitlock et al. (2017), “2017 Montana Climate Assessment”.

[31] Romero-Lankao et al. (2014), “North America.”

[32] I. T. Stewart, D. R. Cayan, and M. D. Dettinger (2005), “Changes toward Earlier Streamflow Timing across Western North America,” Journal of Climate 18.

[33] Whitlock et al. (2017), “2017 Montana Climate Assessment”.

[34] SB Rood et al. (2008), “Declining Summer Flows of Rocky Mountain Rivers: Changing Seasonal Hydrology and Probable Impacts on Floodplain Forests,” Journal of Hydrology 349, no. 3-4.

[35] Stewart, Cayan, and Dettinger (2005), “Changes toward Earlier Streamflow Timing across Western North America.”

[36] Romero-Lankao et al. (2014), “North America.”

[37] Rood et al. (2008), “Declining Summer Flows of Rocky Mountain Rivers: Changing Seasonal Hydrology and Probable Impacts on Floodplain Forests.”

[38] C. H. Luce and Z. A. Holden (2009), “Declining Annual Streamflow Distributions in the Pacific Northwest United States, 1948–2006,” Geophysical Research Letters 36, no. L16401.

[39] Leppi et al. (2012), “Impacts of Climate Change on August Stream Discharge in the Central-Rocky Mountains.”

[40] N. Mantua, I. Tohver, and A. Hamlet (2010), “Climate Change Impacts on Streamflow Extremes and Summertime Stream Temperature and Their Possible Consequences for Freshwater Salmon Habitat in Washington State,” ibid.102, no. 1-2.

[41] D. Isaak et al. (2012), “Climate Change Effects on Stream and River Temperatures across the Northwest Us from 1980-2009 and Implications for Salmonid Fishes,” ibid.113, no. 2.

[42] Whitlock et al. (2017), “2017 Montana Climate Assessment”.

[43] Romero-Lankao et al. (2014), “North America.”

[44] Whitlock et al. (2017), “2017 Montana Climate Assessment”.

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