A24D-08
Measuring the Impact of Rising CO2 and CH4 on the Surface Energy Balance

Tuesday, 15 December 2015: 17:45
3004 (Moscone West)
Daniel Feldman1, William Collins1, Sebastien Biraud1, David D Turner2, Eli Jay Mlawer3, P Jonathan Gero4, Shaocheng Xie5, Timothy Shippert6 and Margaret S Torn1, (1)Lawrence Berkeley National Laboratory, Berkeley, CA, United States, (2)NOAA Norman, Norman, OK, United States, (3)Atmospheric and Environmental Research, Lexington, MA, United States, (4)University of Wisconsin, Madison, WI, United States, (5)Lawrence Livermore National Laboratory, Livermore, CA, United States, (6)Pacific Northwest National Laboratory, Richland, WA, United States
Abstract:
We use observations at the North Slope of Alaska (NSA) and Southern Great Plains (SGP) ARM sites to improve understanding both of the distribution of CO2 and CH4and their influence on the surface energy balance. We use aircraft and ground-based in situ data to characterize the temporal distribution of these greenhouse gases, and spectroscopic observations to derive their collocated surface radiative forcing.

The spectroscopically-measured surface radiative forcing from rising CO2 is 0.2 W/m2/decade at both sites, with a seasonal cycle of 0.2 W/m2. This finding is largely consistent with theoretical predictions, providing robust evidence of radiative perturbations to the Earth’s surface energy budget due to anthropogenic influences.

The contribution from CH4 to the surface energy balance is more spatially and temporally heterogeneous. The ground-based measurements of CH4 at NSA and SGP indicate rising atmospheric concentrations except for a hiatus from 1995-2005, while more recent aircraft profiles indicate that concentrations in the boundary layer and free troposphere are correlated at NSA and decorrelated at SGP. The probability density functions of boundary layer concentrations of CH4 at NSA show little skew, but at SGP show positive skewness, which increased with the introduction of nearby fossil-fuel extraction. The correlated increases in atmospheric measurements of C2H6 and CH4that only occur at SGP are consistent with an anthropogenic influence there.

Time-series of spectroscopically-measured CH4 surface radiative forcing at SGP and NSA also indicate positive trends of 0.1 W/m2/decade associated with the end of the hiatus, marked seasonal cycles, and little skew at NSA and a positive skew at SGP. The combination of in situ and spectroscopic measurements at these sites enables the quantification of surface radiative forcing from anthropogenic CH4.

Implications are discussed for how advanced spectroscopic remote sensing measurements of CH4 can be used to quantify the impact of fossil fuel extraction on surface energy budget.

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