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Monday, May 11, 2015

Empirical Evidence: Oceans Make Climate

Updated May 11 with text added at the end.
You only have to compare Sea Surface Temperatures (SST) from HADSST3 with estimates of Global Mean Surface Temperatures (GMST) from Hadcrut4 and RSS.

This first graph shows how global SST has varied since 1850. There are obvious changepoints where the warming or cooling periods have occurred.

This graph shows in green Hadcrut4 estimates of global surface temperature, including ocean SST, and near surface air temperatures over land. The blue line from RSS tracks lower tropospheric air temperatures measured by satellites, not near the surface but many meters higher. Finally, the red line is again Hadsst3 global SST All lines use 30-month averages to reduce annual noise and display longer term patterns.

Strikingly, SST and GMST are almost synonymous from the beginning until about 1980. Then GMST diverges with more warming than global SST. Satellite TLT shows the same patterns but with less warming than the surface. Curious as to the post 1980s patterns, I looked into HADSST3 and found NH SST warmed much more strongly during that period.

This graph shows how warming from circulations in the Northern Pacific and Northern Atlantic drove GMST since 1980. And it suggests that since 2005 NH SST is no longer increasing, and may turn toward cooling.

Surface Heat Flux from Ocean to Air

Now one can read convoluted explanations about how rising CO2 in the atmosphere can cause land surface heating which is then transported over the ocean and causes higher SST. But the interface between ocean and air is well described and measured. Not surprisingly it is the warmer ocean water sending heat into the atmosphere, and not the other way around.

The graph displays measures of heat flux in the sub-tropics during a 21-day period in November. Shortwave solar energy shown above in green labeled radiative is stored in the upper 200 meters of the ocean. The upper panel shows the rise in SST (Sea Surface Temperature) due to net incoming energy. The yellow shows latent heat cooling the ocean, (lowering SST) and transferring heat upward, driving convection.

From

An Investigation of Turbulent Heat Exchange in the Subtropics
James B. Edson

“One can think of the ocean as a capacitor for the MJO (Madden-Julian Oscillation), where the energy is being accumulated when there is a net heat flux into the ocean (here occurring to approximately November 24) after which it is released to the atmosphere during the active phase of the MJO under high winds and large latent heat exchange.”

http://www.onr.navy.mil/reports/FY13/mmedson.pdf

Conclusion

As we see in the graphs ocean circulations change sea surface temperatures which then cause global land and sea temperatures to change. Thus, oceans make climate by making temperature changes.

On another post I describe how oceans also drive precipitation, the other main determinant of climate. Oceans make rain, and the processes for distributing rain over land are shown here: https://rclutz.wordpress.com/2015/04/30/here-comes-the-rain-again/

And a word from Dr. William Gray:

“Changes in the ocean’s deep circulation currents appears to be, by far, the best physical explanation for the observed global surface temperature changes (see Gray 2009, 2011, 2012, 2012). It seems ridiculous to me for both the AGW advocates and us skeptics to so closely monitor current weather and short-time climate change as indication of CO2’s influence on our climate. This assumes that the much more dominant natural climate changes that have always occurred are no longer in operation or have relevance.”

http://www.icecap.us/
 Indeed, Oceans Make Climate, or as Dr. Arnd Bernaerts put it:
“Climate is the continuation of oceans by other means.”
Update May 11, 2015

Kenneth Richards provided some supporting references in a comment at Paul Homewood’s site. They are certainly on point especially this one:

“Examining data sets of surface heat flux during the last few decades for the same region, we find that the SST 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.”

That quote is from Servain et al, unfortunately behind a paywall.  The paper is discussed here:
http://hockeyschtick.blogspot.ca/2014/09/new-paper-finds-climate-of-tropical.html

Full comment from Richards:
http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00651.1

The surface of the world’s oceans has been warming since the beginning of industrialization. In addition to this, multidecadal sea surface temperature (SST) variations of internal [natural] origin exist. Evidence suggests that the North Atlantic Ocean exhibits the strongest multidecadal SST variations and that these variations are connected to the overturning circulation. This work investigates the extent to which these internal multidecadal variations have contributed to enhancing or diminishing the trend induced by the external radiative forcing, globally and in the North Atlantic. A model study is carried out wherein the analyses of a long control simulation with constant radiative forcing at preindustrial level and of an ensemble of simulations with historical forcing from 1850 until 2005 are combined. First, it is noted that global SST trends calculated from the different historical simulations are similar, while there is a large disagreement between the North Atlantic SST trends. Then the control simulation is analyzed, where a relationship between SST anomalies and anomalies in the Atlantic meridional overturning circulation (AMOC) for multidecadal and longer time scales is identified. This relationship enables the extraction of the AMOC-related SST variability from each individual member of the ensemble of historical simulations and then the calculation of the SST trends with the AMOC-related variability excluded. For the global SST trends this causes only a little difference while SST trends with AMOC-related variability excluded for the North Atlantic show closer agreement than with the AMOC-related variability included. From this it is concluded that AMOC [Atlantic meridional overturning circulation] variability has contributed significantly to North Atlantic SST trends since the mid nineteenth century.

 http://link.springer.com/article/10.1007%2Fs00382-014-2168-7
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 [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. 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 Atlantic meridional overtuning circulation [AMOC] and the subtropical cells are required to explain the observations.

 http://www.nature.com/ncomms/2014/141208/ncomms6752/full/ncomms6752.html
The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the global climate system, responsible for a large fraction of the 1.3 PW northward heat transport in the Atlantic basin. Numerical modelling experiments suggest that without a vigorous AMOC, surface air temperature in the North Atlantic region would cool by around 1–3 °C, with enhanced local cooling of up to 8 °C in regions with large sea-ice changes. Substantial weakening of the AMOC would also cause a southward shift of the inter-tropical convergence zone, encouraging Sahelian drought, and dynamic changes in sea level of up to 80 cm along the coasts of North America and Europe.

Natural science

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