Ten Human Fingerprints on Climate

Posted on April 29, 2012

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Climate School

  1. Humanity tosses 30 billion tones of CO² into the atmosphere every year.  (See CO2 Information Analysis Center.)  Where does it go?  It is possible to answer this question because fossil fuel carbon is different from the carbon in the atmosphere.

 Explanation:  There are two stable carbon isotopes, isotopes that don’t break down over time, carbon 12 and carbon 13.  Plants prefer carbon 12, and tend to incorporate it a little more efficiently than carbon 13.  There’s always a higher ratio of carbon 12 in plants than in the surrounding atmosphere, but this has no net effect on the system so long as the carbon in the plants continues to re-enter the system.  Does this always happen?  Nope.  Think fossil fuels.  Fossil fuel deposits of coal, oil and gas, etc., are nothing more than ancient organic matter pulled out of circulation long ago.  Over immense periods of time, because of plants systematically favouring carbon 12 over carbon 13, the ratio of these two types of carbon in the carbon cycle has slowly but inevitably changed in favour of carbon 13.  Hence the ratio of carbon 12 to carbon 13 is different in fossil carbon than in our modern atmosphere, and that difference is significant and measurable.  Fossil fuels are relatively higher in carbon 12.  The modern atmosphere is relatively higher in carbon 13.

  1. The addition of carbon 12-rich CO² to the atmosphere from the burning of fossil  fuels should be measurable by a change in the carbon 12/carbon 13 balance in the atmosphere.  This change has been measured.  The amount of carbon 12 has gone up proportionately.  See Manning 2006.
  2. The atmosphere does not account for all the CO² produced by humanity.  Some of it dissolves in the ocean.  Examination of old coral has shown that the level of carbon from CO² in the oceans has built up over time. See Pelejero 2005.
  3. Burning fossil carbon requires oxygen, two atoms of oxygen for each atom of carbon which has been turned into CO².  The oxygen used is now missing from the atmosphere, and that has been measured as well.  See Manning 2006 again.

So what? says Simple Sam, my in-house climate change denier.  Just because CO² levels are rising in the atmosphere and humans are responsible for it, that doesn’t prove the essential point, that CO² and greenhouse gases are the cause of our present warming.  What are your proofs of that? he asks.

  1. CO² heats up the planet by preventing light of particular wavelengths from escaping the atmosphere into space.  Satellites have measured less heat escaping into space at the particular wavelengths blocked by CO².  See Harries 2001, Griggs 2004, and Chen 2007.
  2. And as we would expect, we have measured more heat coming in (see Philipona 2004, Wang 2009) and the extra heat coming in is heat at those specific wavelengths blocked by CO² (see Evans 2006.)  The signature of CO² in points 5 and 6 represents direct observational evidence of the effect of greenhouse gases on warming.
  3. CO² is transparent to the high intensity light being emitted by the Sun during the day, letting it in, but blocks low intensity infrared red light being emitted at night when the Earth cools.  Direct warming from the Sun would warm more during the day, but warming from greenhouse gases has the opposite effect, warming more at night.  In fact, nighttime warming is proceeding faster than daytime warming, pointing to the influence of greenhouse gases.  See Braganza 2004 and Alexander 2006.
  4. Since greenhouse gases block heat from escaping from below, we should find progressively less heat reaching the upper atmosphere from below.  Most of the heat should be trapped in the lower atmosphere.  Thus the stratosphere should be cooling, which it is. See Jones 2003.
  5. Also with warming, the lower atmosphere would be expected to expand and the boundary between it and the layer above it would thus be expected to rise.  The boundary between the lower atmosphere (the troposphere) and the upper atmosphere (the stratosphere) is called the tropopause, and it has indeed risen.  See Santer 2003.
  6. An even higher layer of the atmosphere, above the stratosphere, called the ionosphere or the thermosphere, can be expected to shrink with cooling.  This also has been observed.  See Laštovi?ka 2006 and my post about space litter.

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Note:  The above graphic, most of the links and the majority of the arguments are courtesy of Skeptical Science.  This is just the way that I say it, and any errors that may have crept in are mine.  The original may be found here.