
Secular trends and climate drift in coupled ocean‐atmosphere general circulation models
Author(s) -
Covey Curt,
Gleckler Peter J.,
Phillips Thomas J.,
Bader David C.
Publication year - 2006
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005jd006009
Subject(s) - climatology , climate model , environmental science , forcing (mathematics) , atmosphere (unit) , climate change , transient climate simulation , climate commitment , sea ice , general circulation model , carbon dioxide in earth's atmosphere , ocean current , abrupt climate change , global warming , atmospheric sciences , effects of global warming , meteorology , oceanography , geology , geography
Coupled ocean‐atmosphere general circulation models (coupled GCMs) with interactive sea ice are the primary tool for investigating possible future global warming and numerous other issues in climate science. A long‐standing problem with such models is that when different components of the physical climate system are linked together, the simulated climate can drift away from observation unless constrained by ad hoc adjustments to interface fluxes. However, 11 modern coupled GCMs, including three that do not employ flux adjustments, behave much better in this respect than the older generation of models. Surface temperature trends in control run simulations (with external climate forcing such as solar brightness and atmospheric carbon dioxide held constant) are small compared with observed trends, which include 20th century climate change due to both anthropogenic and natural factors. Sea ice changes in the models are dominated by interannual variations. Deep ocean temperature and salinity trends are small enough for model control runs to extend over 1000 simulated years or more, but trends in some regions, most notably the Arctic, differ substantially among the models and may be problematic. Methods used to initialize coupled GCMs can mitigate climate drift but cannot eliminate it. Lengthy “spin‐ups” of models, made possible by increasing computer power, are one reason for the improvements this paper documents.