Since 1911, the climate in eastern Utah and western Colorado has become warmer, especially the minimum temperatures. There is also some indication that the region has seen increased precipitation. After a cooling trend from the 1940s through the 1960s, the trend towards warmer and wetter conditions has occurred since the 1970s. These general trends in regional temperature and precipitation are matched in surrounding sites. Large decade-to-decade and site-to-site variability was noted in the temperature and precipitation data.
In 1911, the Wright brothers were flying in North Carolina, and the Ford Model T had been on the road for three years. In the new towns of eastern Utah and western Colorado, weather observers were beginning to record daily, monthly, and annual temperature and precipitation data. In eleven of those towns, those climate data continue to be recorded to this day. This study is an analysis of the trends in those data.
To explore how these averages have changed with time, all sites (called Study Sites) within the forecast area with strong climate records back to 1911 were analyzed, including maximum and minimum temperatures and precipitation. There are eleven sites within eastern Utah and western Colorado that have mostly unbroken climate records back to 1911. In eastern Utah these sites include Vernal, Moab, Blanding, and Bluff. Western Colorado sites are Steamboat Springs, Grand Junction, Crested Butte, Gunnison, Montrose, Telluride, and Silverton.
Study Sites within the NWS Grand Junction Forecast Area
Climate data complications.
With the exception of Grand Junction and Montrose, all sites have some missing data. For example Silverton had significant missing data between 1977 and 1983. Telluride’s long and strong climate record ended in 2008. Blanding’s climate record started in late 1912.
There are climate sites in the forecast area that have minimized these potential problems, those sites located in National Parks and Monuments (Park Sites). On these protected lands, site, land use, and instrument changes have been minimized. A disadvantage of these climate sites is that most of their observations began much later than 1911. There are nine Park Sites in the forecast area that extend back into the 1960s: Flaming Gorge NRA, Ouray NWR, Dinosaur NM, Colorado NM, Canyonlands NP The Neck and Needles, Natural Bridges NM, Hovenweep NM, and Mesa Verde NP. Arches NP climate data began in the 1980s so was not used.
National Parks and Monuments Sites
One final climate data set was gathered, that is sites surrounding the forecast area (Surrounding Sites). Surrounding Sites and Study Sites can be compared to see if any local trends also occur within the wider geographic region. Ten Surrounding Sites were chosen: to the north Lander WY; to the east Ft Collins, Denver, and Rocky Ford CO; to the south Taos, Albuquerque, and Las Cruces NM (author’s previous hometown); to the southwest Prescott AZ; and to the northwest Salt Lake City, and Heber City UT.
These three data sets, Study, Park, and Surrounding Sites, were individually averaged and plotted together to compare climate trends over the last 100 years. The data sets were analyzed in 10 year and in 30 year periods, the latter shown here to examine how the climate average has changed. Note, the Park and Surrounding Sites have lower average elevations compared to the Study Sites. This shows in their offset towards warmer and drier conditions in the graphs.
1. Comparing the Study Sites and the Parks and Monument data sets for the climate periods 1961-1990 through 1981-2010. These data sets show very similar temperature trends through the 30 year period. Both maximum temperatures have risen 0.4 degrees F and the minimum temperatures have risen 1.1 F. The exact same rate of change seen in these two data sets indicate that any site change problems with the Study Sites are not significant, at least at this resolution. Precipitation rates have also increased during this time frame, by a small 0.08 inch in the Parks Site’s data, by 0.59 inch in the Study Site’s data.
Temperature data from all three data sets Study, Park, and Surrounding Sites, show a strong correlation. All three data sets show an increasing warming trend over the last 30 years, strongest in the minimum temperatures. This fits well with NOAA’s national analysis of the current climate normal warming trend and also fits well with the climate model projections.
Thanks to co-workers Julie Malingowski and Aldis Strautins for map building, and Jeff Colton for web formatting and patiently listening to my analysis over several weeks.