Craig Williamson
Global Change Limnology Laboratory

Dr. Craig Williamson

Craig Williamson

The questions that we ask in our Global Change Limnology Lab deal with how solar ultraviolet radiation, climate change, predation risk, and trophic interactions influence pelagic ecosystem structure and function. We view lakes as sentinels, integrators, and regulators of environmental change, with an emphasis on deciphering the most valuable sentinels of climate change. Projects take us all over the world from regions in the U.S. such as northeastern Pennsylvania, Alaska, Lake Tahoe, and the Beartooth Mountains, to the Canadian Rockies, Argentina, and New Zealand. Our questions are field based, but our approaches range from small scale laboratory and field experiments to the ecosystem level, and involve comparative as well as experimental studies.

View Publications or Education and Professional Employment.

Lake observatory networks play a central role in the broader goals of the Global Change Limnology Laboratory.

  • Many generations of scientists from the lab pitched in to help set up overwintering temperature and oxygen strings and retrieve the lab's profiling buoy, ARTHUR. (Photo: J Brentrup, K Rose, N Berry, L Adkins, and R Pilla, Lacawac Sanctuary, PA)
  • Lakes serves as sentinels -or sensors- in the landscape, providing signals about changes in the surrounding environment. (Photo: Beauty Lake, MT)
  • Using buoys and sensors, we collect high frequency lake data that interface with lake ecological observatory networks. (Photo: Jennie Brentrup, Lake Lacawac, PA)
  • Field samples help us to better understand a lake's sentinel responses and the resulting biotic consequences. (Photo: Grinnell Lake, MT)
  • Students couple laboratory and field experiments to answer their research questions. (Photo: Matt Meeks, Lake Lacawac, PA)
  • Collaboration with other scientists enables us to answer large-scale ecological questions. (Photo: LEOW Meeting, Lacawac Sanctuary, PA)

Lab News

Ultraviolet Radiation and Climate Change

As part of his service to the scientific and global community, Craig serves on several national and international panels and review boards including the United Nations Environment Programme Environmental Effects Assessment Panel (UNEP EEAP) on ozone depletion and climate change, and the Freshwater Indicators Technical Team for the National Climate Assessment (NCA FITT).

The UNEP EEAP keeps all of the nations that ratified the Montreal Protocol informed about the current status of ozone depletion and climate change through an annual report to the United Nations. The latest full UNEP EEAP report appeared in the special issue of Photochemical and Photobiological Sciences. Smaller annual reports are also published each year, with major reports every 4 years.

The National Climate Assessment is a report to the United States President and Congress as well as to the public. The latest NCA report appeared in 2014. For more information on the National Climate Assessment visit

2015 Ozone Hole Fourth Largest on Record

Ozone Holes

While the Montreal Protocol is successfully curbing the concentrations of ozone depleting chemicals in Earth's atmosphere, the ozone hole is still reaching close to the 2006 all-time record in both maximum size and minimum ozone concentrations.

Relevant Publications

Williamson, C. E., R. Zepp, R. Lucas, S. Madronich, A. T. Austin, C. L. Ballare, M. Norval, B. Sulzberger, A. Bais, R. McKenzie, S. Robinson, D.-P. Hader, N. D. Paul, J. F. Bornman. 2014. Solar ultraviolet radiation in a changing climate. Nature Climate Change 4: 434-441. PDF

Grimm, N. B., F. S. Chapin, B. Bierwagen, P. Gonzalez, P. M. Groffman, Y. Q. Luo, F. Melton, K. Nadelhoffer, A. Pairis, P. A. Raymond, J. Schimel, and C. E. Williamson. 2013. The impacts of climate change on ecosystem structure and function. Frontiers in Ecology and the Environment 11: 474-482. Other highlights of the National Climate Assessment were published in this same special issue of FEE.

For more information on ozone depletion and UV radiation

NASA Ozone Hole Watch: This site has images, archives, and educational information on the Antarctic ozone hole.

World Meteorological Organization (WMO) Ozone: This site has information on ozone, educational materials, and the WMO ozone bulletins- current and archives.

Total Ozone Mapping Spectrometer (TOMS): This site has information on monitoring and mapping of both current and historical global ozone. This resource is useful for estimating UV exposure at different locations on Earth.

UV Disaster avoided - what if there were no Montreal Protocol? This site has images and graphs of projected ozone and UV exposure on Earth with and without the reduction of ozone-depleting substances according to the Montreal Protocol.

What UV Does to Your Skin An ultraviolet camera shows the damage done to skin.