A paper published today in Climate Dynamics finds that warming of the surface of tropical Atlantic Ocean since 1975 was not due to an increase of greenhouse gases, and was instead due to natural ocean and atmospheric oscillations.
“After a decrease of SST by about 1 °C during 1964–1975, most apparent in the northern tropical region, the entire tropical basin warmed up. That warming was the most substantial (>1 °C) in the eastern tropical ocean and in the longitudinal band of the intertropical convergence zone.”
“Examining data sets of surface heat flux during the last few decades for the same region, we find that the SST [sea surface temperature] warming was not a consequence of atmospheric heat flux forcing.
In other words, sea surface temperatures did not rise as a consequence of increased “radiative forcing” from greenhouse gases.
“Conversely, we suggest that long-term SST warming drives changes in atmosphere parameters at the sea surface, most notably an increase in latent heat flux, and that an acceleration of the hydrological cycle induces a strengthening of the trade winds and an acceleration of the Hadley circulation. These trends are also accompanied by rising sea levels and upper ocean heat content over similar multi-decadal time scales in the tropical Atlantic.”
“…it is likely that changes in ocean circulation involving some combination of the [natural] Atlantic meridional overtuning circulation [AMOC] and the subtropical cells are required to explain the observations.”