Flying over thin ice
DOI: 10.1063/PT.3.1275
Kwok and Untersteiner reply: As discussed in our article, an average heat imbalance at the surface on the order of 1 W · m–2 is required to explain the observed thinning of the Arctic sea ice cover during the past three decades. And the level of scientific understanding of the geophysical processes responsible for delivering that heat to the sea ice cover remains low. Comparatively, the current best estimate for the globally averaged radiative forcing by persistent linear aircraft contrails 1 from 2000 to 2005 is +0.010 W · m–2, where a positive forcing leads to mean surface warming and a negative forcing to cooling. Even though uncertainties are involved in determining global values of contrail forcing, that level of forcing, if distributed uniformly over the globe, is unlikely to account for the observed thinning of the Arctic ice cover.
References
1. P. Forster et al., in Climate Change 2007: The Physical Science Basis—Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change S. Solomon et al., eds.,Cambridge U. Press, New York (2007), p. 129. 9780521705967
More about the Authors
Ron Kwok. (ronald.kwok@jpl.nasa.gov) Jet Propulsion Laboratory Pasadena, California.
Norbert Untersteiner. University of Washington Seattle.
