In order to achieve the Ultimate State of Enlightenment re: Climate Change Policy, we have been encouraged to swallow Al Gore’s panicky conclusion (that We Must Act Now! to Combat AGW!) in one giant leap of faith. Doubters are marginalized with the label “Global Warming Deniers”.
Using simple mathematical and decision-making principles, you, too, can be a bona-fide Climate Change Skeptic, and not a Global Warming Denier.
The Act Now! conclusion depends on at least three separate Premises, each of which must be independently judged to be True. Each of these propositions is a matter of science, engineering and/or economics. Each one involves its own degree of uncertainty.
Those Premises are:
Premise A: The earth (a.k.a. Mother Gaia) is experiencing a warming trend; and
Premise B: An increase in the atmospheric concentration of certain gases, principally carbon dioxide, is sufficient to cause Global Warming. Further, human activity is the primary cause of the increase; and
Premise C: Humankind can take effective actions to adapt to or to mitigate the warming trend.
One may totally agree with Premise A, but be uncertain with regard to Premise B: is it possible that warming causes carbon dioxide to increase and not vice-versa? And even if we had solid proof of Premises A and B (thereby proving Anthropogenic Global Warming, AGW), if there are no solutions then Premise C is False.
The Laws of Probability let us consider the joint probability of two or more independent events by multiplying the independent probabilities. Thus, by multiplying the chance that Premise A is True times the chance that Premise B is True (symbolically, P(A) x P(B)), we calculate the chance that both A and B are True (in this example, the chance that AGW is True: there is Global Warming and it is caused by manmade CO2).
Take it one more step: the chance that the AGW hypothesis is True and that we can effectively fight it is:
P(A) x P(B) x P(C)
In its 2007 Summary Report, the International Panel on Climate Change addresses the uncertainty of each of these premises, as good scientists should. As for Premise A, IPCC says “Warming of the climate system is unequivocal…,” implying 100% certainty: P(A)=100%.
Premise B: “There is very high confidence [>90%] that the net effect of human activities since 1750 has been one of warming. … Most of the observed increase in global average temperatures since the mid-20th century is very likely [i.e., P(B)>90%] due to the observed increase in anthropogenic GHG [greenhouse gas] concentrations. It is likely [>66%] that there has been significant anthropogenic warming over the past 50 years averaged over each continent (except Antarctica).” [Emphasis in original.]
As for Premise C, the IPCC’s positions are less straightforward. Their report addresses “adaptation” and “mitigation” as two separate but complementary strategies for dealing with Climate Change. On the topic of adaptation, the IPCC says: “A wide array of adaptation options is available, but more extensive adaptation than is currently occurring is required to reduce vulnerability to climate change. There are barriers, limits and costs, which are not fully understood.”
“There is high confidence [80% +/-] that there are viable adaptation options that can be implemented in some sectors [this emphasis mine] at low cost, and/or with high benefit-cost ratios. However, comprehensive estimates of global costs and benefits of adaptation are limited.” …
[On mitigation:] “Both bottom-up and top-down studies indicate that there is high agreement and much evidence of substantial economic potential for the mitigation of global GHG emissions over the coming decades that could offset the projected growth of global emissions or reduce emissions below current levels … . While top-down and bottom-up studies are in line at the global level … there are considerable differences at the sectoral level.”
IPCC doesn’t quantify “high agreement”, so let’s go with the value they give to “high confidence”: around 80% certainty, P(C)=80%. That number applies if we take Premises A & B as given; if there is no AGW, then there is no remedy needed; the “high benefit-cost ratios” on which they base their high confidence in a (To Be Determined) mitigation strategy.
So in this admittedly simplistic analysis, one that admittedly does not take into account all the complexity, caveats and weasel words in the IPCC report, can we estimate IPCC’s confidence in both the need and efficacy of a Climate Change Solution?
100% x 90% x 80% = 72%
OK, so even allowing for the uncertainty of estimating uncertainties, the IPCC thinks that somewhere around 3 chances in 4 that A) the earth is warming and B) manmade CO2 is the cause and C) we should do something about it.
To put it another way, there’s a 1 in 4 chance that the remedies are a waste, either because they’re not needed, or because they’re ineffective. Or both.
Wow. It’s sure not being sold to the public that way.
It’s not like the IPCC doesn’t have a dog in the fight. Heck, Climate Change is part of their name. Can we really expect an unbiased judgment to come from them? The Accepted Truth of the Climate Change Hypothesis is why the organization exists. We expect Archer-Daniels-Midland to have a bias toward corn based ethanol, or Peabody Coal and ExxonMobil to favor fossil fuels. A scientist in any of these organizations who did not support the primary product would be, ahem, severely limiting his or her upward mobility within the organization. It would be naïve to think the same kind of bias does not exist within an organization called the International Panel on Climate Change.
In Part II, I take a stab at assessing the uncertainty for myself.