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Scenarios of world anthropogenic emissions of air pollutants and methane up to 2030

07/2006;
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    ABSTRACT: The influence of anthropogenic emissions on aerosol distributions and the hydrological cycle are examined with a focus on monsoon precipitation over the Indian subcontinent, during January 2001 to December 2005, using the European Centre for Medium-Range Weather Forecasts-Hamburg (ECHAM5.5) general circulation model extended by the Hamburg Aerosol Module (HAM). The seasonal variability of aerosol optical depth (AOD) retrieved from the MODerate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellite is broadly well simulated (R ≈ 0.6–0.85) by the model. The spatial distribution and seasonal cycle of the precipitation observed over the Indian region are reasonably well simulated (R ≈ 0.5 to 0.8) by the model, while in terms of absolute magnitude, the model underestimates precipitation, in particular in the south-west (SW) monsoon season. The model simulates significant anthropogenic aerosol-induced changes in clear-sky net surface solar radiation (dimming greater than −7 W m−2), which agrees well with the observed trends over the Indian region. A statistically significant decreasing precipitation trend is simulated only for the SW monsoon season over the central-north Indian region, which is consistent with the observed seasonal trend over the Indian region. In the model, this decrease results from a reduction in convective precipitation, where there is an increase in stratiform cloud droplet number concentration (CDNC) and solar dimming that resulted from increased stability and reduced evaporation. Similarities in spatial patterns suggest that surface cooling, mainly by the aerosol indirect effect, is responsible for this reduction in convective activity. When changes in large-scale dynamics are allowed by slightly disturbing the initial state of the atmosphere, aerosol absorption in addition leads to a further stabilization of the lower troposphere, further reducing convective precipitation.
    Journal of Geophysical Research 04/2013; 118:2938-2955. · 3.17 Impact Factor
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    01/2010;
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    ABSTRACT: Of the natural forcings causing short-term climatic variations, volcanism, along with its climatic impact, is perhaps the best understood. The primary net result of the impact is the reduced receipt of solar energy at Earth's surface due to the scattering of incoming solar radiation by secondary sulfate aerosols formed from volcanic sulfur. The quantitative effects can be measured in energy-balance-based climate models, which require validation using high-quality paleoclimatic and paleovolcanic data. An important advancement in the effort to understand the role of volcanism in climate change in the recent decade is the significant improvement in paleovolcanic records from polar ice cores, represented by long records with unprecedented temporal accuracy and precision, and by the potential to identify climate-impacting stratospheric eruptions in the records. Other improvements include (1) the investigation of long-term relationship between eruptions (including super-eruptions) and climate variations, beyond an eruption's radiative impact of up to a few years; (2) a better understanding of the response to volcanic perturbation of feedback mechanisms in the climate system; and (3) the limited role of volcanic eruptions in the era of human-induced greenhouse warming. Urgent research/investigation is needed to evaluate the geoengineering proposition to counteract greenhouse warming by injecting sulfur dioxide into the stratosphere, which is based on the significant cooling effects of stratospheric volcanic eruptions, and its serious unintended consequences. WIREs Clim Change 2010 1 824–839 DOI: 10.1002/wcc.76For further resources related to this article, please visit the WIREs website
    Wiley Interdisciplinary Reviews: Climate Change. 10/2010; 1(6):824 - 839.

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