“Sources of Uncertainty in Long-Term Climate Projections” – PCC Summer Institute 2018

by Sarah Ragen and Hannah Director

On September 12-14, 2018, members of the UW community and invited guests gathered at UW’s Friday Harbor Labs for the Program on Climate Change’s annual Summer Institute. The topic this year was “Sources of Uncertainty in Long-Term Climate Projections.” Participants attending the institute were introduced to many issues that affect how we quantify the uncertainty related to long-term climate projections.

Organizers Kyle Armour, UW Oceanography and Atmospheric Sciences, and Aaron Donohoe, UW Polar Science Center/Applied Physics, pulled together speakers from many fields whose work touched on climate change uncertainty.  The talks covered these general topic areas:

  • Communicating uncertainty and making decisions: Ann Bostrom, Susan Joslyn, Gernot Wagner
  • Global temperature uncertainty: Adrian Raftery, Cristi Proistosescu, Mark Zelinka, Nikki Lovenduski
  • Hydrologic cycle uncertainty: Gerard Roe, Brian Soden, Abby Swann
  • Uncertainty in impacts: Paul Kushner, David Battisti, Kelly McCusker

An overall takeaway from the speakers’ presentations was that the scientific uncertainty in climate projections comes from a broad range of issues and no single academic discipline researches all of them. Uncertainties related to climate projections are affected not only by our knowledge of the physical response of the climate system, but also by uncertainties in human behavior. Substantial challenges remain in integrating these uncertainties that arise across disciplines and presenting them in a way that is useful to policy makers and the general public. While academic disciplines can tend toward insularity, for a topic as all-encompassing as climate change, knowing how to connect ideas from different fields is critical. Tackling climate change requires building understanding of the fundamental physical science, identifying societal and economic impacts, and communicating this information.

Photo Credit: Kyle Armour
The PCC and Friday Harbor Labs hosted over 85 participants, including graduate students, postdocs, faculty, and visitors, at our annual 2018 Summer Institute/FHL Symposium.

The complexity of the issue can be daunting — at times it seems that we will never fully understand how the entire Earth system works now, let alone how it will respond to rising anthropogenic greenhouse gases. However, the point was made that we do know enough to enact policies to reduce emissions and mitigate climate change’s effects. Professor David Battisti of UW Atmospheric Sciences put it bluntly by saying, “climate science is done,” meaning that while there is value in continuing to understand the Earth and its response to emissions, but that the physical science knowledge needed to address climate change is established.

The benefit and importance of the PCC Summer Institute is the space it creates for the free exchange of knowledge across different disciplines. Researchers, professors, industry professionals, and students can share ideas and make connections across arbitrary academic borders. After this Summer Institute, consensus among attendees was that though quantifying uncertainty and continuing to better our understanding of climate change is important, we also need to compel individual, societal, and global action to minimize the extent the climate changes and prepare for changes that can no longer be avoided.