This is an archived article that was published on sltrib.com in 2017, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.
Ten years ago, we were members of a team that prepared a report summarizing scientific knowledge of climate change and its potential impacts on Utah for Gov. Jon Huntsman's Blue Ribbon Advisory Council on Climate Change.
The report, entitled Climate Change and Utah: The Scientific Consensus, concluded that there was very high confidence that human-generated increases in greenhouse gas concentrations, not natural climate variations, were responsible for most of the global warming during the past 50 years. It was clear that Utah was warming, with the average temperature during the prior decade about 2˚F warmer than the average for the previous 100 years.
We projected that ongoing greenhouse gas emissions at or above current levels would further alter the Earth's climate, producing global temperature, sea level, and snow and ice changes greater than those observed during the 20th century. In Utah, this would yield a decline in natural snowfall and snowpack, particularly in lower-to-mid elevation areas, an earlier and less intense average spring runoff, increased heat wave and drought frequency and severity, more algal abundance in lakes, and increased wildfire intensity.
If we were preparing such a report today, these conclusions would be even more confident and sobering. Globally averaged temperatures continue to climb, with 2015 and 2016 the hottest years on record. It is now apparent that the Greenland ice sheet is losing mass and the total mass loss from the world's glaciers is accelerating.
In Utah, we have not had a year with a below average temperature (relative to the 20th century average) since 1993. Studies show that the recent drought in the Colorado River Basin is the first on record that was caused not only by a lack of precipitation, but runoff losses to increased evaporation and transpiration, snowpack sublimation, and growing season length due to higher temperatures.
The most recent studies estimate that nearly all of the warming since the mid 20th century is human caused. Without increases in greenhouse gas concentrations due to human activity, global temperatures would not have changed appreciably.
Projections of future warming suggest an increase in global temperatures of 2 to 9˚F during the 21st century, with the former reflecting a manageable outcome if the sensitivity of the climate to increasing greenhouse gas concentrations is small and we take aggressive actions to reduce emissions. The latter, which would make Park City hotter than present-day Salt Lake City, reflects a high-consequence outcome if the sensitivity of the climate to increasing greenhouse-gas concentrations is large and we follow a high carbon emission pathway into the future.
Such warming may have some benefits, such as improved agricultural production in high latitude regions, a decline in winter deaths and injuries, and the potential for ice-free shipping in the Northwest Passage.
Nobody wins, however, with sea level rise due to the great concentration of population and infrastructure in coastal areas. In Utah, it is difficult to imagine a net benefit as temperatures increase and droughts become more frequent and severe. With ongoing emissions and long-term warming, the decline of our lower-to-mid elevation snowpack will continue, and eventually there will be snowpack declines in our high-elevation mountains, with consequences for water resources, winter sports, and tourism.
We encourage Utahns, especially our elected leaders, to recognize that the so-called climate "debate" is not between two equally credible scientific viewpoints. There is overwhelming evidence that human activity is causing climate change.Let us instead debate the actions that might be taken to address this challenge and determine the climate that our children and grandchildren will inherit.
Jim Steenburgh, Tim Garrett, John Horel and Thomas Reichler are professors of atmospheric sciences and Dave Bowling is a professor of biology at the University of Utah. Rob Gillies is director of the Utah Climate Center. David Long is the director of the Brigham Young University Center for Remote Sensing. The views expressed here are those of the authors and do not necessarily reflect those of their institutions.