NCAR-DOE

The NCAR model version used here is the NCAR-DoE global coupled model (sometimes referred to as the Washington-Meehl coupled model). Simulations of 20th century climate and projections of climate into the 21st century were conducted with a global coupled climate model without flux adjustment. The global coupled climate model used in these experiments has an atmospheric component with rhomboidal 15 (R15) resolution (roughly 4.5º latitude by 7.5º longitude) with 9 levels, mass flux convection and a cloud albedo feedback scheme; a global 1º by 1º 20-level ocean; and dynamic and thermodynamic sea ice. Characteristics of this model are described in Meehl and Washington (1995), Washington and Meehl (1996) and Meehl (1997) for a basic description of a 1% per year CO2 increase experiment.

The climate change experiment used here starting in the year 1900 using greenhouse gas radiative forcing (represented by "equivalent CO2") observed during the 20th century, and extending greenhouse gas forcing to the year 2036 by increasing CO2 1% per year compound after 1990. Climate system responses in the perturbed experiment are marked not only by greater warming at high latitudes in the winter hemisphere, but also by a global "El Nino-like" pattern in surface temperature, precipitation, and sea level pressure. This is characterized by relatively greater increase of SST in the central and eastern equatorial Pacific compared to the west, a shift of precipitation maxima from the western Pacific to the central Pacific, mostly decreases of Asian-Australian monsoon strength, lower pressure over the eastern tropical Pacific, deeper midlatitude troughs in the north and south Pacific, and higher pressure over Australasia.

We acquired the results from this experiment from the IPCC Data Distribution Centre in 1999. The greenhouse gas only change fields used in SCENGEN are calculated as the difference in climate between the 30-year means of years 2011-2036 and 1961-90 in the greenhouse gas only forced simulation. The global warming by 2011-2036, with respect to 1961-90, was 2.8deg C and the increase in global precipitation was 2.31%, yielding a global precipitation sensitivity of 0.8% per degree Celsius warming. The climate sensitivity of the same atmospheric model, coupled to a mixed-layer ocean, was estimated to be 4.6deg C.

Mean monthly precipitation pattern correlation coefficient = 0.59

References

Meehl,G.A. (1997) Modification of surface fluxes from component models in global coupled models J.Climate, 10, 2811-2825.

Meehl,G.A. and Washington,W.M. (1995) Cloud albedo feedback and the super greenhouse effect in a global coupled GCM Climate Dynamics, 11, 399-411.

Washington,W.M. and Meehl,G.A. (1996) High latitude climate change in a global coupled ocean-atmosphere-sea ice model with increased atmospheric CO2 J.Geophys. Res., 101, 12,795-12,801.