Climate Change – Evaluating the Evidence

Roger Pielke Jr. reports here that the Australian Prime Minister proposes to form a citizens’s assembly on climate change. She says

And so today I announce that if we are re-elected, I will develop a dedicated process – a Citizens’ Assembly – to examine over 12 months the evidence on climate change, the case for action and the possible consequences of introducing a market-based approach to limiting and reducing carbon emissions.


Pielke finds problems with the last part. My problem is with examining the evidence on climate change. Given that the climate science is highly polarised, with a lot of complex arguments, this is not something that your average citizen can pronounce upon. Also, given that on one side you have a consensus of experts pronouncing the science is settled, with it being widely promoted that the opposition are just spokespeople for the fossil fuel lobby, there will be a vast majority in support of action and a small minority of dogged skeptics.

The only way for a consensus to be formed objectively is for the panel to act as a jury, with

  1. Clear guidelines as to what constitutes evidence, and levels of evidence to sort out the facts and strongly-verified science, from the, weak circumstantial evidence, and hearsay.*
  2. For a clearly defined barrier to establish the need for action. Like in a criminal trial under English common law, where you have to establish beyond reasonable doubt. The barrier may be set lower (like in civil cases), but it still needs to be there.
  3. To clearly separate the science from the policy. That is to clearly take into account the costs, benefits and risks of policy changes.


*To be clearer, the levels of evidence in decreasing order are.

  1. Facts
  2. Established or independently verified (& not rebutted) science.
  3. Peer-reviewed statistically verified science.
  4. Other peer-reviewed science based on circumstantial evidence.
  5. Papers by advocacy groups.
  6. Hearsay. E.g. “The vast majority accept…..”
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