The tenth IMSC, Beijing, China, 2007 - International Meetings on ...

European trends contain large NAO-related signals, of which a major unknown part may
be unrelated to the anthropogenic signal. <strong>The</strong>refore, we also examine the consistency of
recent and projected changes after subtracting the NAO signal in both the observations and in
the projections. It turns out that even after the removal of the NAO signal, the pattern of trends
in the observations are similar to those projected by the models. At the same time, the
magnitude of the trends is considerably reduced and closer to the magnitude of the change in
the projections.
Detection of external influence on trends of atmospheric storminess and northern oceans wave
heights
Speaker: Xiaolan L. Wang
Xiaolan L. Wang
Climate Research Division, ASTD, STB, Environment Canada, Toronto, Ontario
Xiaolan.Wang@ec.gc.ca
Val R. Swail, Francis W. Zwiers, Xuebin Zhang,Yang Feng
Climate Research Division, ASTD, STB, Environment Canada, Toronto, Ontario
<strong>The</strong> atmospheric storminess (as inferred from geostrophic wind energy) and ocean
wave heights have increased in the cold seasons over the past half century in the
high-latitudes of the northern hemisphere (especially the northeast North Atlantic in boreal
winter), and have decreased in more southerly northern latitudes. This study shows that these
trend patterns contain a detectable response to external forcing (i.e., both natural and
anthropogenic forcing). <strong>The</strong> signal of external influence is found to be strongest in the winter
hemisphere, that is, in the northern hemisphere in January-February-March and in the
southern hemisphere in July-August-September. However, the magnitude of the estimated
response to the forcing, which was obtained directly from climate models in the case of
geostrophic wind energy and indirectly via an empirical downscaling procedure in the case of
ocean wave heights, is significantly less than the magnitude of the observed changes in these
parameters.
Detection of Human Influence on 20th Century Precipitation Trends
Speaker: Xuebin Zhang
Xuebin Zhang
Environment Canada
Xuebin.Zhang@ec.gc.ca
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