[1] We find a consistent and statistically significant increase in the intensity of future extreme winter precipitation events over the western United States, as simulated by an ensemble of regional climate models (RCMs) driven by IPCCAR4 global climate models (GCMs). All eight simulations analyzed in this work consistently show an increase in the intensity of extreme winter precipitation with ...

A high proportion of the uncertainty in the decline of Arctic sea ice thickness in recent global climate models can be explained by the uncertainty in the ice thickness in the late 20th century. Experiments with one model indicate that this sensitivity to the mean state remains even when ice-albedo feedback is eliminated from the model. The magnitude of ice-albedo feedback is quantified and fou...

[1] An ice-ocean model has been used to investigate the effect of vertical mixing on the circulation of the Atlantic Water layer (AL) in the Arctic Ocean. The motivation of this study comes from the disparate AL circulations in the various models that comprise the Arctic Ocean Model Intercomparison Project (AOMIP). It is found that varying vertical mixing significantly changes the ocean’s strat...

Four versions of the same global climate model, one with horizontal resolution of 1.8◦×3.6◦ and three with 0.2◦×0.4◦, are employed to evaluate the role of ocean bottom topography and viscosity on the spatial structure of the deep circulation. This study is motivated by several recent observational studies that find subsurface floats injected near the western boundary of the Labrador Sea most of...

[1] The main uncertainty in anthropogenic forcing of the Earth’s climate stems from pollution aerosols, particularly their ‘‘indirect effect’’ whereby aerosols modify cloud properties. We develop a new methodology to derive a measurement-based estimate using almost exclusively information from an Earth radiation budget instrument (CERES) and a radiometer (MODIS). We derive a statistical relatio...

[1] Comparison of polar sea ice results from 11 major global climate models (GCMs) and satellite-derived observations for 1979–2004 reveals that each of the models is simulating annual cycles that are phased at least approximately correctly in both hemispheres. Each is also simulating various key aspects of the observed ice cover distributions, such as winter ice not only throughout the central...

Statistical downscaling methods seek to model the relationship between large scale atmospheric circulation, on say a European scale, and climatic variables, such as temperature and precipitation, on a regional or subregional scale. Downscaling is an important area of research as it bridges the gap between predictions of future circulation generated by General Circulation Models (GCMs) and the e...

Actual and insolation-weighted Northern Hemisphere snow cover and sea ice are binned by latitude bands for the years 1973–2002. Antarctic sea-ice is also analyzed for the years 1980–2002. The use of insolation weighting provides an improved estimate of the radiative feedbacks of snow cover and sea-ice into the atmosphere. One conclusion of our assessment is that while a decrease in both areal a...

Although much of the energy gained by the climate system over the last century has been stored in the oceans, continental energy storage remains important to estimate the Earth’s energy imbalance and also because crucial positive climate feedback processes such as soil carbon and permafrost stability depend on continental energy storage. Here for the first time, 32 general circulation model sim...

Aerosols affect the climate system by changing cloud characteristics in many ways. They act as cloud condensation and ice nuclei, they may inhibit freezing and they could have an influence on the hydrological cycle. While the cloud albedo enhancement (Twomey effect) of warm clouds received most attention so far and traditionally is the only indirect aerosol forcing considered in transient clima...