Carbon cycle questions

Source: Climate Etc.

Judith Curry


by Judith Curry

I just finished listening to Murry Salby?s podcast on Climate Change and Carbon.  Wow.

The abstract for his talk is here:


Chair of Climate, Macquarie University

Atmospheric Science, Climate Change and Carbon ? Some Facts

Carbon dioxide is emitted by human activities as well as a host of natural processes. The satellite record, in concert with instrumental observations, is now long enough to have collected a population of climate perturbations, wherein the Earth-atmosphere system was disturbed from equilibrium. Introduced naturally, those perturbations reveal that net global emission of CO2 (combined from all sources, human and natural) is controlled by properties of the general circulation ? properties internal to the climate system that regulate emission from natural sources. The strong dependence on internal properties indicates that emission of CO2 from natural sources, which accounts for 96 per cent of its overall emission, plays a major role in observed changes of CO2Independent of human emission, this contribution to atmospheric carbon dioxide is only marginally predictable and not controllable.

Professor Murry Salby holds the Climate Chair at Macquarie University and has had a  lengthy career as a world-recognised researcher and academic in the field of Atmospheric Physics. He has held positions at leading research institutions, including the US National Center for Atmospheric Research, Princeton University, and the University of Colorado, with invited professorships at universities in Europe and Asia. At Macquarie University, Professor Salby uses satellite data and supercomputing to explore issues surrounding changes of global climate and climate variability over Australia. Professor Salby is the author of Fundamentals of Atmospheric Physics, and Physics of the Atmosphere and Climate due out in 2011. Professor Salby?s latest research makes a timely and highly-relevant contribution to the current discourse on climate.

The podcast for his talk is here.  Unfortunately there is no video so you can?t see his graphs.  But the talk is very lucid, you can certainly get the point.  The entire podcast is an hour, with his formal presentation about a half hour, and questions for the remaining half hour.

This talk was given in June at the IUGG meeting in Melbourne Australia, and apparently created quite a stir.    A journal paper is in press, expected to be published in about 6 months.  Some of the results will be in his forthcoming book Physics of the Atmosphere and Climate that will be available Sept 30.

Andrew Bolt has some reactions in the Herald Sun:

Salby?s argument is that the usual evidence given for the rise in CO2 being man-made is mistaken. It?s usually taken to be the fact that as carbon dioxide concentrations in the atmosphere increase, the 1 per cent of CO2 that?s the heavier carbon isotope ratio c13 declines in proportion. Plants, which produced our coal and oil, prefer the lighter c12 isotope. Hence, it must be our gasses that caused this relative decline.

But that conclusion holds true only if there are no other sources of c12 increases which are not human caused. Salby says there are ? the huge increases in carbon dioxide concentrations caused by such things as spells of warming and El Ninos, which cause concentration levels to increase independently of human emissions. He suggests that its warmth which tends to produce more CO2, rather than vice versa ? which, incidentally is the story of the past recoveries from ice ages.

The Earth?s carbon cycle is not a topic on which I have any expertise.  A good overview article is provided by NASA?s earthobservatory.

Climate models have begun to include an interactive carbon cycle in the CMIP5 simulations.  NASA has been trying to launch a satellite to measure global carbon, an effort which remains troubled and plagued by continuing delays.

JC comments:  If Salby?s analysis holds up, this could revolutionize AGW science.  Salby and I were both at the University of Colorado-Boulder in the 1990’s, but I don?t know him well personally.  He is the author of a popular introductory graduate text Fundamentals of Atmospheric Physics.  He is an excellent lecturer and teacher, which comes across in his podcast.  He has the reputation of a thorough and careful researcher.  While all this is frustratingly preliminary without publication, slides, etc., it is sufficiently important that we should start talking about these issues.  I?ll close with this text from Bolt?s article:

He said he had an ?involuntary gag reflex? whenever someone said the ?science was settled?.

?Anyone who thinks the science of this complex thing is settled is in Fantasia.?