UM Researcher Contributes Frost-Free Seasonal Data to National Climate Assessment

May 06, 2015

University of Montana Professor John Kimball. Photo credit: Todd Goodrich

MISSOULA – University of Montana Professor John Kimball is among a group of researchers nationwide who are contributing data to the National Climate Assessment.

This month marks the one-year anniversary of the U.S. Global Change Research Program’s 2014 National Climate Assessment, an effort spearheaded by the federal government to fulfill a need for reliable, scientific information about current and future changes, impacts and effective response options to a changing climate.

“Today is the anniversary of the release of the 2014 National Climate Assessment,” said Melissa Kenney, University of Maryland research assistant professor. “So it’s fitting that the U.S. Global Change Research Program is releasing the first product of a sustained U.S. National Climate Assessment – indicators,”

The USGCRP tasked prominent researchers nationwide to provide scientific data that ultimately can help decision makers understand and respond to climate change. Each technical team will take on a specific indicator of climate change. Based out of Missoula, Kimball is on the technical team that is working on data related to phenology – or the timing of seasonal processes.

Indicators of climate change can communicate key aspects of the changing environment, point out vulnerabilities and inform decisions about policy, planning and resource management. The indicators communicate some of the key aspects of the changing climate, such as temperatures over land and at sea, greenhouse gas levels in the atmosphere, the extent of Arctic sea ice, and related effects in sectors like public health and agriculture.

Some of the indicators show climate-related trends over time, whereas others show the status of resources that may be affected by climate change in the future. Kimball’s team will contribute data for the frost-free season, defined as the number of frost-free days in a year, which reflects the overall warming trend in the climate system.

Kimball developed a nonfrozen season indicator data set at UM, which was selected as one of the indicators to be used in the climate change assessment because it provided data on the entire continental United States and was traceable and defensible.

 Essentially, the data Kimball organized shows how the frost-free season has changed over time. The UM lab uses satellite microwave remote-sensing data to measure when the land is frozen and not frozen. The data set, collected by NASA satellites two times a day since 1979, is one of the longest satellite remote-sensing records available. It shows the worldwide timing and length of the nonfrozen season.

“The timing and duration of that nonfrozen season is particularly important for influencing the timing of vegetation growth and the duration of the growing season,” Kimball said. “Effectively we are defining the frost-freeze season each year, and because we have more than 30 years of data, we can begin to understand decadal changes.”

The data shows that the growing season has increased by about two days each decade in the continental U.S.

“That has a big effect over a 30-year period,” Kimball said. “We are generally getting a growing season that is a week longer.”

This indicator can help decision makers understand and anticipate possible impacts on agricultural and natural resource sectors. For instance, some pests and pathogens affecting forests and crops are projected to benefit from warmer temperatures and longer frost-free seasons. A lengthening frost-free season also may impact habitat conditions and wildfire risk.

“This information will help land managers and politicians plan accordingly,” Kimball said. “But, it also will help inform the public of the kind of environmental changes they are seeing across the nation.”

“This indicator system is a really important first step,” said Anthony Janetos, Boston University Frederick S. Pardee professor and director of The Frederick S. Pardee Center for the Study of the Longer-Range Future. “Not just as a baseline of impacts but also as a way to begin chronicling how we adapt to the impacts we cannot avoid.”

For more information on Kimball’s study, call him at 406-243-4922, email johnk@ntsg.umt.edu or visit http://www.globalchange.gov/browse/indicators/indicator-frost-free-season.

For more information on the national climate assessment, visit http://nca2014.globalchange.gov/

During the past 30 years, there has been an upward trend in the length of frost-free days. Using microwave remote-sensing data from satellites, dates of freeze and thaw can be measured on a daily basis to determine the frost-free growing season. The upper map (right) shows the mean annual frost-free season and the lower map shows the frost-free season annual variation (days) as observed from the satellite record.

Contact: John Kimball, UM professor, Department of Ecosystem and Conservation Sciences, 406-243-4922, johnk@ntsg.umt.edu.