Increased atmospheric carbon dioxide and climate feedback mechanisms

As a consequence of fossil fuel burning, the atmospheric concentration of carbon dioxide has increased from 314 ppm in 1958, when detailed measurements of this quantity began, to a present value of 335 ppm; and it is estimated that during the next century, the CO2 concentration will double relative to its assumed preindustrial value of 290 ppm. Since CO2 is an infrared-active gas, increases in its atmospheric concentration would lead to a larger infrared opacity for the atmospheric which, by normal logic, would result in a warmer Earth. A number of modeling endeavors suggest a 2 to 4 C increase in global mean surface temperature with doubling of the CO2 concentration. But such estimates of CO2-induced warming are highly uncertain because of a lack of knowledge of climate feedback mechanisms. Interactive influences upon the solar and infrared opacities of the Earth-atmosphere system can either amplify or damp a climate-forcing mechanism such as increasing CO2. Climate feedback mechanisms discussed include climate sensitivity, cloudiness-radiation feedback, climate change predictions, and interactive atmospheric chemistry

Trends in World Communication

In today's world communication four major trends can be observed: digitization, consolidation, deregulation, and globalization. It should be a priority on our research agendas to question how these developments affect people's lives across the globe

The Surface Radiation Budget and Cloud Climate Interactions as a Part of CERES

Work that has been completed is described in reprints and preprints, and summaries in terms of broad categories are given as follows: (1) The Relationship between Surface and Satellite Shortwave Radiative Fluxes; (2) Cloud-Climate Interactions in Atmospheric General Circulation Models; (3) Absorption of Shortwave radiation by clouds; (4) Clear-sky atmospheres shortwave radiation; and (5) Surface shortwave radiation measurements

The role of radiation in mesoscale flows: Physics, parameterizations, codes

The topics discussed include the following: an overview of radiation and mesoscale flows and lessons learned from the intercomparison of GCM radiative codes

Surface cloud forcing in the East Pacific stratus deck/cold tongue/ITCZ complex

Author Posting. © American Meteorological Society 2006. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 19 (2006): 392–409, doi:10.1175/JCLI3620.1.Data from the Eastern Pacific Investigation of Climate Studies (EPIC) mooring array are used to evaluate the annual cycle of surface cloud forcing in the far eastern Pacific stratus cloud deck/cold tongue/intertropical convergence zone complex. Data include downwelling surface solar and longwave radiation from 10 EPIC-enhanced Tropical Atmosphere Ocean (TAO) moorings from 8°S, 95°W to 12°N, 95°W, and the Woods Hole Improved Meteorology (IMET) mooring in the stratus cloud deck region at 20°S, 85°W. Surface cloud forcing is defined as the observed downwelling radiation at the surface minus the clear-sky value. Solar cloud forcing and longwave cloud forcing are anticorrelated at all latitudes from 12°N to 20°S: clouds tended to reduce the downward solar radiation and to a lesser extent increase the downward longwave radiation at the surface. The relative amount of solar radiation reduction and longwave increase depends upon cloud type and varies with latitude. A statistical relationship between solar and longwave surface cloud forcing is developed for rainy and dry periods and for the full record length in six latitudinal regions: northeast tropical warm pool, ITCZ, frontal zone, cold tongue, southern, and stratus deck regions. The buoy cloud forcing observations and empirical relations are compared with the International Satellite Cloud Climatology Project (ISCCP) radiative flux data (FD) dataset and are used as benchmarks to evaluate surface cloud forcing in the NCEP Reanalysis 2 (NCEP2) and 40-yr ECMWF Re-Analysis (ERA-40). ERA-40 and NCEP2 cloud forcing (both solar and longwave) showed large discrepancies with observations, being too large in the ITCZ and equatorial regions and too weak under the stratus deck at 20°S and north to the equator during the cool season from July to December. In particular the NCEP2 cloud forcing at the equator was nearly identical to the ITCZ region and thus had significantly larger solar cloud forcing and smaller longwave cloud forcing than observed. The net result of the solar and longwave cloud forcing deviations is that there is too little radiative warming in the ITCZ and southward to 8°S during the warm season and too much radiative warming under the stratus deck at 20°S and northward to the equator during the cold season.This research was supported by grants from the NOAA Office of Global Programs, Pan American Climate Studies

The spectral dimension of longwave feedback in the CMIP3 and CMIP5 experiments

Radiative feedback is normally discussed in terms of the change of broadband flux. Yet it has an intrinsic dimension of spectrum. A set of longwave (LW) spectral radiative kernels (SRKs) is constructed and validated in a similar way as the broadband radiative kernel. The LW broadband feedback derived using this SRK are consistent with those from the broadband radiative kernels. As an application, the SRK is applied to 12 general circulation models (GCMs) from the Coupled Model Intercomparison Project Phase 3 and 12 GCMs from the Coupled Model Intercomparison Project Phase 5 simulations to derive the spectrally resolved Planck, lapse rate, and LW water vapor feedback. The spectral details of the Planck feedback from different GCMs are essentially the same, but the lapse rate and LW water vapor feedback do reveal spectrally dependent difference among GCMs. Spatial distributions of the feedback at different spectral regions are also discussed. The spectral feedback analysis provides us another dimension to understand and evaluate the modeled radiative feedback. Key Points Spectral radiative kernel is developed and validated to get spectral feedback Lapse rate and water vapor feedback have different spectral dependence Spectral kernel provides new information not available from broadband studiesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110043/1/grl52334.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/110043/2/grl52334-sup-0001-readme.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/110043/3/grl52334-sup-0002-Auxiliary_material.pd

An Improved Algorithm for Retrieving Surface Downwelling Longwave Radiation from Satellite Measurements

Zhou and Cess [2001] developed an algorithm for retrieving surface downwelling longwave radiation (SDLW) based upon detailed studies using radiative transfer model calculations and surface radiometric measurements. Their algorithm linked clear sky SDLW with surface upwelling longwave flux and column precipitable water vapor. For cloudy sky cases, they used cloud liquid water path as an additional parameter to account for the effects of clouds. Despite the simplicity of their algorithm, it performed very well for most geographical regions except for those regions where the atmospheric conditions near the surface tend to be extremely cold and dry. Systematic errors were also found for scenes that were covered with ice clouds. An improved version of the algorithm prevents the large errors in the SDLW at low water vapor amounts by taking into account that under such conditions the SDLW and water vapor amount are nearly linear in their relationship. The new algorithm also utilizes cloud fraction and cloud liquid and ice water paths available from the Cloud and the Earth's Radiant Energy System (CERES) single scanner footprint (SSF) product to separately compute the clear and cloudy portions of the fluxes. The new algorithm has been validated against surface measurements at 29 stations around the globe for Terra and Aqua satellites. The results show significant improvement over the original version. The revised Zhou-Cess algorithm is also slightly better or comparable to more sophisticated algorithms currently implemented in the CERES processing and will be incorporated as one of the CERES empirical surface radiation algorithms

Global mean cloud feedbacks in idealized climate change experiments

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94978/1/grl21109.pd