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A re‐evaluation of the coherence between global‐average atmospheric CO 2 and temperatures at interannual time scales
Author(s) -
Park Jeffrey
Publication year - 2009
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2009gl040975
Subject(s) - coherence (philosophical gambling strategy) , environmental science , climatology , global temperature , atmospheric sciences , carbon cycle , lag , carbon dioxide , atmospheric temperature , sink (geography) , global warming , climate change , physics , geology , oceanography , chemistry , ecosystem , geography , cartography , organic chemistry , ecology , computer network , quantum mechanics , computer science , biology
Frequency‐dependent coherence between atmospheric CO 2 and historical temperatures reveals climate feedbacks within Earth's carbon cycle. Coherence between interannual fluctuations in global‐average temperature and atmospheric CO 2 has changed over time. Since 1979, at Mauna Loa and other observation sites, interannual coherence exhibits a 90° phase lag that suggests a direct correlation between temperatures and the time‐derivative of CO 2 . The coherence transition can be explained if the response time of CO 2 to a global temperature fluctuation has lengthened from 6 months to at least 15 months. A longer response time may reflect saturation of the oceanic carbon sink, but a transient shift in ocean circulation may play a role. Coherent annual‐cycle fluctuations in CO 2 and temperature are evident in the 1958–1988 time series, but not since 1979. Coherence of interannual CO 2 variations with gridpoint temperature anomalies are strongest in the tropical oceans.