National Aeronautics and Space Administration

National Climate Assessment

NASA National Climate Assessment (NCA) Activities

NASA Indicators Solicitation Proposals

Development and Testing of Potential Indicators for the National Climate Assessment

Lead PI and Center: Mark Flanner, University of Michigan
Title: Cryosphere Radiative Forcing: An Indicator of Climate Feedback and Environmental Change

The objective of this proposal is to produce, maintain, and publicize a global, time-varying observational dataset of cryosphere radiative forcing (CRF).  This metric of the cryosphere describes its instantaneous influence on Earth's top-of-atmosphere (TOA) solar energy budget. Because TOA energy fluxes fundamentally drive global climate, changes in CRF over time provide a quantitative measure of the amplifying effect of cryospheric evolution on climate change.  CRF also provides a concise indication of the vulnerability or resiliency of the cryosphere to evolving climate and allows cryospheric evolution to be compared, in consistent terms, with direct anthropogenic forcings and feedbacks associated with other environmental changes.  CRF depends not only on coverage of seasonal snow, glaciers and sea-ice, but also on local insolation, cloud cover, snow and ice properties (e.g., thickness and morphology), and the nature of the snow-free surface.  CRF therefore incorporates climate-relevant features of the cryosphere, such as the muted influence of snow on albedo of conifer forests and the amplified influence of sea-ice changes that occur during the summer solstice season, whereas such features are lost in common metrics of snow and sea-ice extent.

We will derive CRF by extending techniques recently applied by the PI to determine  CRF and albedo feedback during 1979-2008.  We will incorporate NASA remote sensing retrievals of surface reflectance, snow presence, sea-ice concentration, cloud cover, and cloud optical thickness with radiative transfer modeling.  We will employ retrievals of land surface albedo when sky conditions permit, and utilize mircrowave retrievals of snow cover under cloudy skies to produce spatially-complete datasets.  Our technique combines retrievals of sea-ice concentration with measurements of age-dependent, seasonally-evolving sea-ice albedo.  We will produce near real-time estimates of CRF using regular releases of MODIS data and preliminary sea-ice concentrations provided daily by the National Snow and Ice Data Center (NSIDC). Global, gridded land snow CRF will be provided at native 0.5 arc-minute resolution, produced every 8 days, and sea-ice CRF on 25 km equal area grids at daily resolution.   We will also provide merged land and sea-ice data on regular 0.5 degree grids at monthly resolution to facilitate easier data analysis and visualization.  Data released to the public will include gridded uncertainty estimates and flags indicating the derivation technique.  The methods we propose are transparent, generalized, and will accommodate new NASA measurements such as those from VIIRS.

Global, hemispheric, and continental averages of CRF will serve as concise indicators of the cryospheric state, and timeseries of these data, normalized to temperature change, will indicate the strength of albedo feedback.  These indicators will therefore serve as important input for the U.S. National Climate Assessment and other assessments such as IPCC reports.  Data produced for this project will be available through University of Michigan and NSIDC websites, allowing users to explore other applications of the data including its potential as a leading indicator of seasonal climate.  Finally, funding for this project will support two early career scientists.