Abstract
Reliability of future global warming projections depends on how well
climate models reproduce the observed climate change over the twentieth
century. In this regard, deviations of the model simulated climate
change from observations, such as a recent “pause” in global warming,
have received considerable attention. Such decadal mismatches between
model simulated and observed climate trends are common throughout the
twentieth century, and their causes are still poorly understood. Here we
show that the discrepancies between the observed and simulated climate
variability on decadal and longer time scale have a coherent structure
suggestive of a pronounced global multidecadal oscillation. Surface
temperature anomalies associated with this variability originate in the
North Atlantic and spread out to the Pacific and Southern oceans and
Antarctica, with Arctic following suit in about 25–35 years. While
climate models exhibit various levels of decadal climate variability and
some regional similarities to observations, noneof the model simulations
considered match the observed signal in terms of its magnitude, spatial
patterns and their sequential time development. These results highlight
a substantial degree of uncertainty in our interpretation of the
observed climate change using current generation of climate models.