Wednesday, March 19, 2014

Global Warming Hasn't Stopped

Much has been made recently in media reports of the so-called "global warming pause" or "hiatus", a slowdown in the rate of increase of mean global surface temperatures over the past 10–15 years, as can be inferred from the graph below.  

Although the causes of this slowdown are still being worked out, when one looks at the Earth's climate system as a whole, it is pretty clear that global warming is continuing unabated.

Global warming affects not just the atmosphere, but also the hydrosphere (i.e., the oceans), the cryosphere (i.e., snow and ice), and the lithosphere (the Earth's crust).  The accumulation of energy produced by global warming thus can be expressed not only as a warming of the atmosphere, but also in terms of a warming of the oceans, melting of ice, or warming of the land surface.

A nice plot showing this energy accumulation is provided in the IPCC Fifth Assessment Report (AR5). The energy accumulation is dominated by deep and upper ocean warming.  The melting of ice and warming of the land surface are much smaller contributors, and the atmosphere even smaller.
Source: IPCC AR5
When one takes this holistic view, it is pretty clear that although the rate of atmospheric surface temperature increase has slowed during the past 10–15 years, we are still seeing a massive accumulation of energy within the Earth's climate system.  Thus, although the causes of the slowdown in surface temperature increase are still being ferreted out (see this Scientific American article for a summary), there is every reason to expect that the upward trend will eventually return.   At this point, we can't stop global warming, we can only hope to contain it.


  1. The units on the graph are ZJ (zettajoules) 10^21. Wow. Whole lotta energy! Thanks Jim as always for your posts.

    1. By 2100, we may reach 1 YJ, a yottajoule, equal to 10^24 Joules!

      It is quite unfathomable. 275 ZJ is equal to the energy in 3 billion 20 kT nuclear explosions...or the energy required for every one of the 7 billion people of the world to drive a car 20 million miles each...or the energy equivalent of providing every American with electricity for 20,000 years.

    2. Rather than "unfathomable", we can call it "astronomical" :-). If I remember right, the Earth intercepts 175,000 Terrawatts of solar energy. A climate forcing of 0.5 W/m2 integrated across the planet adds up to a total of about 250 TerraWatts, a much smaller number, but the equivalent of 4 small fission bombs per second, and it is accumulating all the time. More at