Complete liberty of contradicting and disproving our opinion is the very condition, which justifies us in assuming its truth for purposes of action. On no other terms can a being with human faculties have any rational assurance of being right. John Stuart Mill, On Liberty, 1859
The recently hacked or leaked emails from the University of East Anglia Climate Research Unit (CRU) suggests data manipulation, a lack of scientific consensus, inadequate peer-reviewing, unprofessional and unscientific conduct, obfuscation, collusion, and possibly corruption. The CRU is basically a clearing-house for informing the United Nations Intergovernmental Panel on Climate Change (IPCC) of the science of anthropogenic global warming (AGW).
The IPCC was charged with understanding the scientific basis of the risk of human-induced climate change, its potential impacts, and options for adaptation and mitigation. The IPCC engaged scientists to review and summarise peer-reviewed climate literature, and contribute to the writing of assessment reports and their accompanying summaries for policymakers. The aim of these reports and summaries is to provide the science that will support the processes of negoiating the control of greenhouse gas emission levels.
Scientists mostly wrote these reports, but also politicians, diplomats and representatives of non-governmental organisations have the final say on the reports’ presentations, and what is written and included in the Summary for Policymakers’ reports. It is the Summary for Policymakers’ reports that underpin governments’ actions to climate change, as well as providing the intent of the well-known Stern and Garnaut reports, and to help keep advocates “on message”. Many of the scientists named in the CRU emails were involved in the writing of these reports.
The scientific basis of the risk of human-induced climate change rests on empirical observations and climate modelling. It is from this modelling that the fears of runaway global warming or catastrophic climate have originated, prompting Prime Minister Kevin Rudd to proclaim climate change “is the greatest moral issue of our time”.
Our understanding of climatic processes is incomplete and subject to natural climate variability and the anthropogenic effects of deforestation, land clearing, altered albedos and the urban heat island effect, and so on. The climate modelling used to determine the risk of human-induced climate change rests not only on data observed and recorded from these processes but also on parameters - implicit and explicit assumptions, and gross approximations.
The main climate modelling assumptions are:
- positive amplifier feedback mechanism;
- an anthropogenic atmospheric carbon dioxide (CO2) residence time of 50 to well over 200 years;
- the exchange of naturally-derived CO2 between the atmosphere and ocean is in static equilibrium;
- that CO2 is well mixed in the atmosphere; and
- the inclusion of the buffer or Revelle factor, based on two à priori assumptions: that anthropogenic CO2 will redistribute itself according to the present atmosphere and ocean inventories; that assumed pre-industrial era atmospheric CO2 values are preset (at around 280ppm).
What does this mean?
- the feedback mechanism, can be either positive or negative - the science here is definitely not settled;
- average atmospheric CO2 residence time is approximately four years (range 2 to 25 years), as determined by empirical measurements and supported by over 90 per cent of the peer-reviewed literature;
- the atmosphere-ocean CO2 exchange is in dynamic equilibrium and also includes anthropogenic CO2 in its exchange, as governed by Henry’s Law;
- atmospheric mixing between the hemispheres takes about two years; and
- the buffer or Revelle factor gives the modelling an inbuilt bias that helps produce the assumed long anthropogenic CO2 residence time; without this assumption there is no discernable warming.
The IPCC web site shows the location of anthropogenic CO2 emissions. Over 90 per cent of all anthropogenic CO2 emissions are released in the northern hemisphere, mostly between 30 and 60 degrees north latitude. If the IPCC’s assertion that anthropogenic CO2 has a long atmospheric residence time is correct then there should be an accumulation of atmospheric CO2 in the northern hemisphere yet the annual average CO2 levels in this mid-latitude band of the northern hemisphere are indistinguishable from anywhere else in the world and no appreciable difference, apart from seasonal variations, has ever been detected. The detection of seasonal variations would not be possible without a short CO2 residence time.
This rapid turnover of CO2 provides a simple explanation as to why there is no apparent accumulation of CO2 in the 30-60 degree northern hemisphere latitude band. Most anthropogenic CO2 emissions are consumed by vegetation and taken up by the oceans within a year or two after emission, possibly even faster.
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