Jeffrey Park, Geophys. Res. Lett., 36 (2009), A re-evaluation of the coherence between global-average atmospheric CO2 and temperatures at interannual time scales

Geophysical Research Letters, 36 (2009) L22704; DOI: 10.1029/2009GL040975

A re-evaluation of the coherence between global-average atmospheric CO₂ and temperatures at interannual time scales 

A re-evaluation of the coherence between global-average atmospheric CO2 and temperatures at interannual time scales

Jeffrey Park

Department of Geology and Geophysics, Yale University, New Haven, CT, U.S.A.

Abstract

Frequency-dependent coherence between atmospheric CO₂ and historical temperatures reveals climate feedbacks within Earth's carbon cycle. Coherence between interannual fluctuations in global-average temperature and atmospheric CO₂ 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 CO₂. The coherence transition can be explained if the response time of CO₂ 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 CO₂ and temperature are evident in the 1958–1988 time series, but not since 1979. Coherence of interannual CO₂ variations with gridpoint temperature anomalies are strongest in the tropical oceans.

Link to abstract:  http://www.agu.org/pubs/crossref/2009/2009GL040975.shtml