Seasonality of biological and physical systems as indicators of climatic variation and change

Jake F. Weltzin, Julio L. Betancourt, Benjamin I. Cook, Theresa M. Crimmins, Carolyn A.F. Enquist, Michael D. Gerst, John E. Gross, Geoffrey M. Henebry, Rebecca A. Hufft, Melissa A. Kenney, John S. Kimball, Bradley C. Reed, Steven W. Running

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Evidence-based responses to climate change by society require operational and sustained information including biophysical indicator systems that provide up-to-date measures of trends and patterns against historical baselines. Two key components linking anthropogenic climate change to impacts on socio-ecological systems are the periodic inter- and intra-annual variations in physical climate systems (seasonality) and in plant and animal life cycles (phenology). We describe a set of national indicators that reflect sub-seasonal to seasonal drivers and responses of terrestrial physical and biological systems to climate change and variability at the national scale. Proposed indicators and metrics include seasonality of surface climate conditions (e.g., frost and freeze dates and durations), seasonality of freeze/thaw in freshwater systems (e.g., timing of stream runoff and durations of lake/river ice), seasonality in ecosystem disturbances (e.g., wildfire season timing and duration), seasonality in vegetated land surfaces (e.g., green-up and brown-down of landscapes), and seasonality of organismal life-history stages (e.g., timings of bird migration). Recommended indicators have strong linkages to variable and changing climates, include abiotic and biotic responses and feedback mechanisms, and are sufficiently simple to facilitate communication to broad audiences and stakeholders interested in understanding and adapting to climate change.

Original languageEnglish (US)
Pages (from-to)1755-1771
Number of pages17
JournalClimatic Change
Issue number4
StatePublished - Dec 2020

Bibliographical note

Funding Information:
Kenney’s research team provided research and coordination support to the technical team, which was supported by National Oceanic and Atmospheric Administration grant NA09NES4400006 and NA14NES4320003 (Cooperative Climate and Satellites-CICS) at the University of Maryland/ESSIC. Acknowledgments

Funding Information:
The authors acknowledge the support provided by A.C. Janetos, chair of the Indicator Work Group (IWG) under the National Climate Assessment and Development Advisory Committee (NCADAC). Members of the Indicators Technical Teams, NCADAC IWG, and Kenney?s NCIS research team are included in Kenney et al. (2014). Earlier versions of this report were reviewed by K. Bruce Jones. Amanda Staudt, the IWG Forest Indicators Technical Team led by Linda Heath, and members of the IWG. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. government. This publication honors of Tony Janetos, who constantly challenged our team to think bigger and to assure we were rigorous in our vision.

Publisher Copyright:
© 2020, This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.


  • Assessment
  • Climate variability and change
  • Decision support
  • Metrics
  • Seasonality


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