ScienceDaily (Nov. 27, 2009) — The world's oceans are absorbing less carbon dioxide (CO2), a Yale geophysicist has found after pooling data taken over the past 50 years. With the oceans currently absorbing over 40 percent of the CO2 emitted by human activity, this could quicken the pace of climate change, according to the study, which appears in the November 25 issue of Geophysical Research Letters.
Pacific Ocean at sunset. The world's oceans are absorbing less carbon dioxide, a Yale geophysicist has found after pooling data taken over the past 50 years. With the oceans currently absorbing over 40 percent of the CO2 emitted by human activity, this could quicken the pace of climate change, (Credit: Copyright Michele Hogan)
Jeffrey Park, professor of geology and geophysics and director of the Yale Institute for Biospheric Studies, used data collected from atmospheric observing stations in Hawaii, Alaska and Antarctica to study the relationship between fluctuations in global temperatures and the global abundance of atmospheric CO2 on interannual (one to 10 years) time scales. A similar study from 20 years ago found a five-month lag between interannual temperature changes and the resulting changes in CO2 levels. Park has now found that this lag has increased from five to at least 15 months.
"No one had updated the analysis from 20 years ago," Park said. "I expected to find some change in the lag time, but the shift was surprisingly large. This is a big change."
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Journal Reference:
Park et al. A re-evaluation of the coherence between global-average atmospheric CO2 and temperatures at interannual time scales. Geophysical Research Letters, 2009; 36 (22): L22704 DOI: 10.1029/2009GL040975
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, Connecticut, USA
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.
Received 14 September 2009; accepted 22 October 2009; published 25 November 2009.
Citation: Park, J. (2009), A re-evaluation of the coherence between global-average atmospheric CO2 and temperatures at interannual time scales, Geophys. Res. Lett., 36, L22704, doi:10.1029/2009GL040975.
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