Researcher: John Walsh
Funding Source: NSF/OPP (Cooperative Agreement)
Collaborators: Vladimir Kattsov (Russia), James Overland (NOAA/PMEL),William
Chapman (University of Illinois), Asgeir Sorteberg (University of Bergen, Norway),Peter Larsen
(The Nature Conservancy)
The project goal is to narrow the uncertainty in projections of future arctic climate change. This requires a determination of the extent to which recent arctic climate changes (the past 100–150 years) are anthropogenic and/or natural in origin.
The project focuses on arctic climate changes over the past 100–150 years and future changes through the 21st century. The changes of interest span the atmosphere, ocean, ice, and land components of the arctic system. Climate models are providing the vehicle for assessment of the greenhouse signature of change, but the models’ credibility must be established through validation of simulations of past climate. Through such an evaluation against observational data for the past several decades, we are attempting to determine optimal strategies for compositing model simulations of the past and future. The simulations of the past will establish the greenhouse signature in the Arctic, while the 21st-century simulations by the optimal subset of models may permit a narrowing of the uncertainty in the projections. This study must include evaluations of the various sources of uncertainty, which can be placed into three categories: 1) natural (internal) variations, 2) uncertainties in forcing (greenhouse gas and aerosol changes), and 3) across-model differences.
We will partition the uncertainty into the three categories listed above, and will use the results to guide an evaluation of the extent to which recent arctic climate changes are the result of internal variability (e.g., natural modes of the atmospheric circulation) and greenhouse gas changes. The results will also lead to an optimization of arctic climate projections through 2100, accompanied by quantitative measures of uncertainty.
The project synthesizes the vast archive of model simulations (from more than 20 global climate modeling centers) into conclusions concerning the attribution of recent arctic change and into a set of optimal arctic climate projections for use by the scientific community, policymakers, and the broader public.
Funding is also available from the University of Alaska through the Scenarios Network for Alaska Planning (SNAP) and through the NOAA Cooperative Institute for Alaska Research. Both of these projects are for Alaska only (the latter for statistical downscaling), while the NSF-supported work addresses changes over the pan-Arctic scale, including sea ice and the ocean.