Climate Trends from 1911 to 2015 for Selected Sites in Eastern Utah and Western Colorado

How has the climate of eastern Utah and western Colorado been changing? One way to explore this question is to look back at the climate record for sites within this region. If we go back to 1911 there are only 11 sites in eastern Utah and western Colorado with mostly unbroken climate records (Figure 1). A different set of climate records were also analyzed, nine sites within National Parks and Monuments (Figure 2). The Park set would have less problems with urbanization, site location change, or instrumentation changes. A disadvantage to the Park data set is their climate record only generally began in the 1960s.

Figure1. Eleven sites with strong climate records back to 1911.

Figure 2. Nine National Parks and Monuments in eastern Utah and western Colorado. These sites would have minimal or zero problems with urbanization, site or instruementation changes.

These two data sets show strongly similar trends. Maximum temperatures (Figure 3) show little overall trend. Minimum temperatures (Figure 4) show a warming trend since the 1970s. Precipitation graphs (Figure 5) show large variation but with a wet period in the 1980s into the 1990s and a subsequent dry trend.

Figure 3. The graph of forecast maximum temperatures for the 11 Forecast Area sites and nine Parks and Monument sites. The Parks and Mounument sites are offeset warmer because of their lower average elevation. Since the 1930s, you can see some up and down but little overall trend. The latest five years, 2011-2015, are dashed to indicate a different time frame than the decade time increments.

Figure 4. Minimum temperatures graphs for the Forecast Area sites and Park sites. Here we can see a warming trend beginning in the 1970s. Again the Park sites are offset warmer due to their lower elevation. The latest five years are dashed.

Figure 5. precipitation graphs. The Park data set is still offset drier also because of its lower overall elevation. The latest five years are dashed. The two data sets still show a strongly similar overall trend. We can see the dry years in the 1930s, 1950s, 1970s and wet years in the 1980s into the 1990s. The trend since then has been drier.

It is not a given that the eleven forecast area sites are a good representation of any climate trends for the forecast area as a whole. However the Park data set seems to follow the same climate trends and adds confidence to these trends.