Title: Data in support of the study "Climate Response to Negative Greenhouse Gas Radiative Forcing in Polar winter"
Authors: M.G. Flanner, X. Huang, X. Chen, and G. Krinner
Contact: Dr. Mark Flanner flanner@umich.edu
Grant: NSF ARC-1253154 and DOE DE-SC0012969


Key Points:
-Increased GHG concentrations in polar inversion layers cause negative top of atmosphere instantaneous and effective radiative forcing
-Polar and global surface temperatures warm despite this negative radiative forcing
-Surface warming and tropospheric cooling result from high stability and increased surface downwelling longwave flux


Research Overview: 
Greenhouse gas (GHG) additions to Earth’s atmosphere initially reduce global outgoing longwave radiation (OLR), thereby warming the planet. In select environments with temperature inversions, however, increased GHG concentrations can actually increase local OLR. Negative top-of-atmosphere and effective radiative forcing (ERF) from this situation give the impression that local surface temperatures could cool in response to GHG increases. Here we consider an extreme scenario in which GHG concentrations are increased only within the warmest layers of winter near-surface inversions of the Arctic and Antarctic. We find, using a fully coupled Earth system model, that the underlying surface warms despite the GHG addition exerting negative ERF and cooling the troposphere in the vicinity of the GHG increase. This unique radiative forcing and thermal response is facilitated by the high stability of the polar winter atmosphere, which inhibits thermal mixing and amplifies the impact of surface radiative forcing on surface temperature. These findings also suggest that strategies to exploit negative ERF via injections of short-lived GHGs into inversion layers would likely be unsuccessful in cooling the planetary surface.


Methodology: 
The data are model output from climate simulations conducted with the Community Earth System Model (CESM) version 1.0.6


Files contained here are:
- Antarctic_flux_hdr.txt: MODTRAN simulations of spectral irradiance at the surface and top-of-atmosphere for Antarctic winter conditions.  "control" columns represent baseline conditions, and "perturb" columns represent conditions with perturbed CFC-11 concentrations, as described in the paper.

- Arctic_flux_hdr.txt: MODTRAN simulations of spectral irradiance at the surface and top-of-atmosphere for Arctic winter conditions.  "control" columns represent baseline conditions, and "perturb" columns represent conditions with perturbed CFC-11 concentrations, as described in the paper.

- age0_timeseries.nc: Monthly history fields from the fully-coupled CESM "control" simulation described in the paper.

- age1_timeseries.nc: Monthly history fields from the fully-coupled CESM "experiment" simulation described in the paper.

- age4_timeseries.nc: Monthly history fields from the prescribed-SST CESM control simulation used to derive effective radiative forcing, as described in the paper.  

- age5_timeseries.nc: Monthly history fields from the prescribed-SST CESM experiment simulation (i.e., with perturbed CFC-11) used to derive effective radiative forcing, as described in the paper.


Use and Access: 
This data set is made available under a Creative Commons Public Domain license (CC0 1.0). 

To Cite Data: 
Flanner, M. G., X. Huang, X. Chen, & G. Krinner (2018). Climate Response to Negative Greenhouse Gas Radiative Forcing in Polar Winter [Data set]. University of Michigan Deep Blue Data Repository. https: //doi.org/10.7302/Z27942W2