final_program_abstracts[1]

11 IMSC Session Program
Present-day interannual variability of surface climate in CMIP3
models and its relation to the amplitude of future warming
Thursday - Parallel Session 2
Simon C. Scherrer
Climate Services, Federal Office of Meteorology and Climatology MeteoSwiss,
Zürich, Switzerland
Interannual variability (IAV) of 2m temperature (T), sea level pressure (SLP) and
precipitation (P) in the CMIP3 20th century model simulations is compared with IAV
in observational and reanalysis data sets. Further the relation between the
representation of T IAV and the amplitude of future warming is investigated.
In the Northern Hemisphere (NH) extratropics, T and SLP IAV are (in contrast to P)
in general well represented although a few models perform much worse than others.
General problem regions are i) sea ice boundary regions, where well known biases in
the mean states exist and ii) the Pacific Ocean and Central Africa where SLP IAV is
consistently underestimated. T and SLP IAV discrepancies are often found in similar
regions and are large in well known bias problem regions in the tropics and subtropics
and high mountain regions. “Bad” IAV representation also occurs in regions with
small biases. T IAV is in general better reproduced on land than on sea and in the
extratropics than in the tropics. Among the “good” IAV models there is no robust
relation between the tropics (sea only) and the extratropics (land only).
The relation between the model’s ability to correctly represent T IAV and projected
temperature changes is slightly negative (more warming for better IAV
representation) but except for the NH summer season not significant when the worst
models in terms of IAV representation are omitted. With exception of NH summer,
this suggests that no robust relations are found between the model’s ability to
correctly represent T IAV and the projected temperature change.
Abstracts 236