Posted by: ericgrimsrud | January 22, 2015

The Litmus Test for global warming

The most commonly used measure of global warming, to date, has been the average of temperatures measured over vast portions of the Earth’s land and ocean surfaces.  The main reason why this measure has been used so extensively is that it is relatively easy to obtain – we live on or regularly travel over those surfaces.  Thus, direct temperature measurements of this type go a long way back – to 1880 and beyond. The latest compilation of such measurements between 1880 and 2014 was shown and discussed in my previous post.

Nevertheless, surface temperatures measurements do not provide the very best and most direct indicator of global warming. This is because only about 3% of the total increased heat of our planet goes to those surfaces described above.

A much better measure of changes in the Earth’s heat content is provided by the changes in the heat content of our oceans – where more than 90% of the increased heat goes.  With that introduction to its importance, I will refer you to the figure shown below recently provided by the National Oceanic and Atmospheric Administration of the USA.

Ocean heat content data to a depth of 2,000 meters, from NOAA.

This figure shows the total heat content of our oceans measured from the top down to a depth of 2000 meters relative to the arbitrarily chosen reference year of 1978 during the period from 1956 to 2014.

This graph clearly shows that the heat content of this large portion of the total oceans has increased greatly over the 60-year period of measurements and has continuously increased every year over the last 25 years. These data clearly put to rest the often heard but erroneous claim that we are presently experiencing a “hiatus” of warming.  The heat content of the Earth has been increasing continuously over the last couple decades and is sure to continue to follow the same trend in the coming years if we proceed with business-as-usual energy policies.  Only the elimination of greenhouse gas emissions can cause this trend to level out and then, many years later, begin to return to pre-industrial levels. All of this will take some time, of course – what is slow to heat up is also slow to cool off.  Since a major portion of our future heating is already in the pipeline due to our already elevated and long-lived level of CO2, it is imperative that we begin to aggressively cut CO2 emissions immediately. Given that fact, our current search for ever more sources of fossil fuels is nothing short of madness and abject stupidity.

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