Friday, May 30, 2014

New paper finds Atlantic Ocean warming since 1975 was natural, not due to greenhouse gases

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. 

According to the authors, 
"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."
Indeed, increases in greenhouse gases cannot significantly heat the oceans.  

Recent climatic trends in the tropical Atlantic

Jacques Servain, Guy Caniaux, Yves K. Kouadio, Michael J. McPhaden, Moacyr Araujo

A homogeneous monthly data set of sea surface temperature (SST) and pseudo wind stress based on in situ observations is used to investigate the climatic trends over the tropical Atlantic during the last five decades (1964–2012). 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. Surprisingly, the trade wind system also strengthened over the period 1964–2012. Complementary information extracted from other observational data sources confirms the simultaneity of SST warming and the strengthening of the surface winds. 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. 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. Though more work is needed to fully understand these long term trends, especially what happens from the mid-1970’s, 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.

2 comments:

  1. But..hurricanes...

    Er, no...physics then. Physics. That's the ticket observations be damned.

    ReplyDelete
  2. Told you so:

    "Before it is safe to attribute a global warming or a global cooling effect to any other factor (CO2 in particular) it is necessary to disentangle the simultaneous overlapping positive and negative effects of solar variation, PDO/ENSO and the other oceanic cycles. Sometimes they work in unison, sometimes they work against each other and until a formula has been developed to work in a majority of situations all our guesses about climate change must come to nought."

    http://www.newclimatemodel.com/the-real-link-between-solar-energy-ocean-cycles-and-global-temperature/

    Stephen Wilde.

    ReplyDelete

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