The AGWs are taking much more interest in ocean heat content, it seems, now that the global atmospheric temperature continues to decline. Logically, ocean heat content is a more rational measure of global warming.
Measurement of ocean temperature has been limited to surface measurements, primarily. But the recent deployment of the ARGO Buoys should allow the determination of ocean heat content with an accuracy previously not possible. By the end of 2003 over 3000 buoys were dispersed in the oceans around the world. The buoys measure ocean temperature and salinity. They descend to 2000 meters and then rise to the surface. Once on the surface they transmit the salinity and temperature data to satellites. Simultaneously the satellite pinpoints the location of the buoy. The results to date show a slight cooling of the Earth’s oceans. The following chart is taken from the data provided by the international group that manages the ARGO program.
To learn more about the ARGO program see
But getting back to ocean heat content, a recent entry by William DiPuccio in Roger Pilke, Sr.’s blog, “Climate Science” discusses ocean heat content. Highlighted are some of his thoughts about ocean heat content versus air temperature a metric:
“Have Changes In Ocean Heat Falsified The Global Warming Hypothesis?” William DiPuccio
Despite a consensus among scientists on the use of ocean heat as a robust metric for AGW, near-surface air temperature (referred to as “surface temperature”) is generally employed to gauge global warming. The media and popular culture have certainly equated the two. But this equation is not simply the product of a naïve misunderstanding. NASA’s Goddard Institute for Space Studies (GISS), directed by James Hansen, and the British Hadley Centre for Climate Change, have consistently promoted the use of surface temperature as a metric for global warming. The highly publicized, monthly global surface temperature has become an icon of the AGW projections made by the IPCC.
However, use of surface air temperature as a metric has weak scientific support, except, perhaps, on a multi-decadal or century time-scale. Surface temperature may not register the accumulation of heat in the climate system from year to year. Heat sinks with high specific heat (like water and ice) can absorb (and radiate) vast amounts of heat. Consequently the oceans and the cryosphere can significantly offset atmospheric temperature by heat transfer creating long time lags in surface temperature response time. Moreover, heat is continually being transported in the atmosphere between the poles and the equator. This reshuffling can create fluctuations in average global temperature caused, in part, by changes in cloud cover and water vapor, both of which can alter the earth’s radiative balance.
Hype generated by scientists and institutions over short-term changes in global temperature (up or down) has diverted us from the real issue: heat accumulation. Heat is not the same as temperature. Two liters of boiling water contain twice as much heat as one liter of boiling water even though the water in both vessels is the same temperature. The larger container has more thermal mass which means it takes longer to heat and cool.
Temperature measures the average kinetic energy of molecular motion at a specific point. But it does not measure the total kinetic energy of all the molecules in a substance. In the example above, there is twice as much heat in 2 liters of boiling water because there is twice as much kinetic energy. On average, the molecules in both vessels are moving at the same speed, but the larger container has twice as many molecules.
Water is a more appropriate metric for heat accumulation than air because of its ability to store heat. For this reason, it is also a more robust metric for assessing global warming and cooling. Seawater has a much higher mass than air (1030 kg/m3 vs. 1.20 kg/m3at 20ºC), and a higher specific heat (4.18 kJ/kg/°C vs. 1.01 kJ/kg/°C for air at 23°C and 41% humidity). One kilogram of water can retain 4.18x the heat of an equivalent mass of air. This amounts to a thermal mass which is nearly 3558x that of air per unit volume.
Some level of time lag will enter into the direction, up or down, that will be evidenced in ocean temperatures. Thus it would seem likely that now that the temperatures are on the decline, it might be years before any change in direction will be seen.
To read all of DiPuccio’s entry click here
For more on this ocean heat content