Ronald Prinn

Abstract Present knowledge of the global properties and surface characteraretics of Mars and the composition and dynamics of its atmosphere are reviewed. The objectives of proposed missions, the exploration strategy, and supporting research and technology ...

Data directory includes prescribed emission in MITgcm for CFC-11 and CFC-12, and MITgcm output under different forcing runs. Code directory includes all the code used to generate plots in the paper entitled "On the Effects of the Ocean on Atmospheric CFC-11 Lifetimes And Emissions" (Wang et al. 2021, PNAS in revision).

ABSTRACT The perfluorocarbons (PFCs) are long-lived potent greenhouse gases with mixing ratios that have been steadily increasing in the modern measurement record that extends from the 1970s. We present optimized emissions from 1973-present of three perfluorocarbons: tetrafluoromethane (CF4), hexafluoroethane (C2F6) and octafluoropropane (C3F8). The dominant sources of the PFCs are primary aluminum and semiconductor production. CF4 also has a significant pre-industrial abundance from the build-up of very small natural emissions. The inversions were performed with atmospheric measurements made by the Advanced Global Atmospheric Gases Experiment (AGAGE) network as well as using stored samples from the Commonwealth Scientific and Industrial Research Organization (CSIRO) Southern Hemisphere archive and from several Northern Hemisphere sources. Inverse estimates of surface flux were derived from the measurements using a discrete Kalman filter, the annual pulse method of Chen and Prinn (J. Geophys. Res., 111, D10307, doi:10.1029/2005JD006058), and a 2D 12-box chemical transport model. CF4 emissions have decreased from ~20 Gg/yr in 1981 to the present value of ~11 Gg/yr. Conversely, C2F6 and C3F8 exhibit an early increase in emissions, peaking much later around 2000 at ~3 Gg/yr and ~1 Gg/yr, respectively, and subsequently declining. The incongruity in the emission profiles is discussed in the context of different relative emissions of CF4 and the other measured PFCs from the two main sources, efforts by the aluminum industry to reduce the emission factor of CF4 (kg CF4 /ton Al), and published emission inventories. In all cases, over 90% of emissions are from the Northern Hemisphere.

ABSTRACT We present a risk management framework for considering climate change impacts in policy analysis, as an alternative to the conventional (deterministic) benefit-cost approach. This approach explicitly accounts for uncertainty, and allows impacts to be considered in their physical units as opposed to monetizing. We demonstrate this framework using an uncertainty analysis of radiative forcing stabilization paths, applying the MIT Integrated Global Systems Model, an integrated assessment model of intermediate complexity. We then discuss key remaining challenges to building on this approach to consider the full range of climate impacts that are relevant to policy.

We quantify the potential future changes in atmospheric aerosol (PM2.5) due to climate mitigation activities in Asia, and assess the impacts of these changes on human health and economic welfare. We combine approaches from atmospheric modeling using the MIT/NCAR CAM aerosol simulation, economic modeling of emissions trajectories using the MIT Emissions Prediction and Policy Analysis (EPPA) model, and health and

Data used to produce figures in the manuscript Evaluating Simplified Chemical Mechanisms within Present-Day Simulations of CESM Version 1.2 CAM-chem (CAM4): MOZART-4 vs. Reduced Hydrocarbon vs. Super-Fast Chemistry by Brown-Steiner, B.; Selin, N. E.; Prinn, R.; Tilmes, S.; Emmons, L.; Lamarque, J.-F.; and Cameron-Smith, P

We describe a new 4D-Var inversion framework for nitrous oxide (N2O) based on the GEOS-Chem chemical transport model and its adjoint, and apply it in a series of observing system simulation experiments to assess how well N2O sources and sinks can be constrained by the current global observing network. The employed measurement ensemble includes approximately weekly and quasicontinuous N2O measurements (hourly averages used) from several long-term monitoring networks, N2O measurements collected from discrete air samples onboard a commercial aircraft (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container; CARIBIC), and quasi-continuous measurements from the airborne HIAPER Pole-to-Pole Observations (HIPPO) campaigns. For a 2-year inversion, we find that the surface and HIPPO observations can accurately resolve a uniform bias in emissions during the first year; CARIBIC data provide a somewhat weaker constraint. Variable emission errors are much more difficult to resolve given the long lifetime of N2O, and major parts of the world lack significant constraints on the seasonal cycle of fluxes. Current observations can largely correct a global bias in the stratospheric sink of N2O if emissions are known, but do not provide information on the temporal and spatial distribution of the sink. However, for the more realistic scenario where source and sink are both uncertain, we find that simultaneously optimizing both would require unrealistically small errors in model transport. Regardless, a bias in the magnitude of the N2O sink would not affect the a posteriori N2O emissions for the 2-year timescale used here, given realistic initial conditions, due to the timescale required for stratosphere–troposphere exchange (STE). The same does not apply to model errors in the rate of STE itself, which we show exerts a larger influence on the tropospheric burden of N2O than does the chemical loss rate over short (< 3 year) timescales. We use a stochastic estimate of the inverse Hessian for the inversion to evaluate the spatial resolution of emission constraints provided by the observations, and find that significant, spatially explicit constraints can be achieved Published by Copernicus Publications on behalf of the European Geosciences Union. 3180 K. C. Wells et al.: Simulation of atmospheric N2O with GEOS-Chem in locations near and immediately upwind of surface measurements and the HIPPO flight tracks; however, these are mostly confined to North America, Europe, and Australia. None of the current observing networks are able to provide significant spatial information on tropical N2O emissions. There, averaging kernels (describing the sensitivity of the inversion to emissions in each grid square) are highly smeared spatially and extend even to the midlatitudes, so that tropical emissions risk being conflated with those elsewhere. For global inversions, therefore, the current lack of constraints on the tropics also places an important limit on our ability to understand extratropical emissions. Based on the error reduction statistics from the inverse Hessian, we characterize the atmospheric distribution of unconstrained N2O, and identify regions in and downwind of South America, central Africa, and Southeast Asia where new surface or profile measurements would have the most value for reducing present uncertainty in the global N2O budget.

Abstract We have measured the absolute reflectivities of four areas on Jupiter between 3200 and 11,200 A with spectral resolution of 5 A (λ 6000 A). The values of the isotropic single-scattering albedos derived are considerably higher than those derived from photometric data of other investigators. These higher values allow a fit to be obtained, using existing atmospheric models, to the observed equivalent widths of the H2 3–0 quadrupole lines. The equivalent widths of several Jovian methane and ammonia absorptions are presented and discussed. The values of Chamberlain's w and q parameters for the CH4 6190 A band are found to be 1.2±0.5 and 240±100, respectively.