Environmental & Climate Sciences Department Seminar

"Carbonaceous Gas and Aerosol Measurements to Validate Models and Verify Emissions"

Presented by Manvendra Dubey, Los Alamos National Laboratory

Monday, November 20, 2017, 11:00 am — Conference Room Bldg 815E

Earth system models rely on accurate representations of processes and emissions that are evaluated using observations. Iterative refinements are crucial for reliable and robust climate assessments, as I will illustrate with following recent case studies:

Carbonaceous aerosol (CA) forcing in current models is prescribed as a balance between the warming by black carbon and the cooling by organic aerosol. However, data show that some organic aerosols called brown carbon absorb sunlight. Furthermore, transparent coatings on black carbon amplify their light absorbing potency by lensing. Such coatings could make black carbon more hydrophilic thereby reducing their lifetime and burden. I will use field and laboratory studies to uncover the fundamental chemistry controlling the optical properties and water affinity of CAs as they age to enable prognostic treatments.

Atmospheric carbon dioxide (CO2) accumulation is moderated by its uptake by forests and oceans that soak up 25% each of the human emissions. How carbon sinks will respond to future climate change is uncertain. I will present observations of daily and seasonal variations of column CO2 and CO over the Amazon rainforest. I will show that both biomass burning and net ecosystem exchange that are out of phase control the seasonal CO2 cycle and are captured well by models. However, the daily CO2 drop driven by photosynthesis is biased low in models, a problem that needs to be fixed.

Atmospheric Methane (CH4) that accounts for 25% of climate forcing is rising after a long hiatus. Potential causes include leaks from shale gas revolution, intensive agriculture, permafrost thaw, expand wetlands or shorter lifetime by higher Hydroxyl. I will review recent findings and focus on our discovery of the methane hot spot over Four Corners, NM attributed to fossil fuel that demonstrated reported emissions were low by a factor of 3. I will close with our development of an automated neural network methane leak detection

Hosted by: Steve Schwartz

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