Natural variability around a man-made warming trend

The average temperatures from all climate stations in Wyoming reveal the progressive upward march of the state's mean temperatures. Gray lines represent all of the overlapping data from the individual stations with a few representative records highlighted in orange (warmest two), blue (coldest two), and black.

Some years are warmer than average, and others cooler, but the random year to year changes, the annual role of the temperature dice, has shifted in favor of more warm years. At many locations, recent "cool" years would have been considered warm in the past, and we just do not experience the extreme cold any more.

Volcanic eruptions in the Tropics (triangles at the bottom a la NASA GISS) produce ash clouds that shade the Earth's atmosphere for several years. The striking cooling (blue bars) produced the only true cold years since 1980.

The graph shows how warming due to greenhouse gas emissions combines with other natural factors to create variation from year to year - even as the overall climate warms.

A cold state losses its coldest nights

Wyoming's rising minimum temperatures

This updated animation shows the rise of the minimum temperatures across Wyoming's climate stations. The gray lines show all of the records, and each individual record is highlighted in black, one after another. The warmest and coldest station are highlighted for comparison in orange and blue.

The minimum temperatures capture an important aspect of the recent climate changes because they reveal the night-time and winter changes. Solar output or effects that block the Sun's rays, like volcanic activity, influence these temperatures less than the loss of heat from Earth's atmosphere. Like the difference between a cloudy night when clouds help trap heat and a crisp clear night when heat escapes to space, years can also vary as heat loss changes. As the abundance of heat trapping gases, like carbon dioxide, has climbed, the coldest temperature have been risen. The trend is well explained by greenhouse gas theory, but not by other hypotheses about global warming, such as those about the Sun.

Some stations show little change compared to others, but the bulk of the state has seen its low temperatures rise. In graph below, the temperatures are plotted compared to the average for each location rather than the absolute temperature, and we see that the range of temperatures across the whole state has trended upward. Some stations have not warmed as dramatically as others, but we have been lacking cool years at any station - even though some recent years have been the coolest of the past decade. 

Just as we had warm and cold fluctuations in the past, we have them now. They just occur around a new, warmer baseline.

A New Record Warm Year

2012 beat out 1934

Wyoming has a new record high annual temperature. The last 30 yrs have been exceptionally warm, but 2012 was an extreme even among the recent years.

Welcome to the Wyoming climate trends blog. 

The goal here is to track changes in the heart of the Rocky Mountain region, and provide updates on a study of Wyoming's climate history published in May 2012:

Recent Wyoming temperature trends, their drivers, and impacts in a 14,000-year context

Climatic Change May 2012, Volume 112, Issue 2, pp 429-447


The study showed that temperatures in places like Yellowstone National Park are now higher than they have been for >6000 years.

This figure shows a comparison of a reconstruction of temperatures going back >12,000 years (left) to the historic observations (right).