Most of the articles under this topic talk about the balance of evidence. Various approaches are described.
We have the mathematical approach, the search for proof, which is a difficult path when it comes to a scientific hypothesis that realisitically cannot be proven. A theory is put forward on the basis of available research and that theory is revised as new research comes to light. It is an incremental path that best describes the accummulated research. That is why the UN's Intergovernmental Panel on Climate Change (IPCC) assigns probabilities on various outcomes.
Over the years, the growing volume of research has led to a firming of the probability (currently greater than 90 percent) that global warming is caused by increasing concentrations of greenhouse gases in the atmosphere and that we are responsible, through the burning of fossil fuels and a range of other activities, for this increase.
There is the betting approach. A reasonable person would not bet against an outcome that carries a 90 percent level of certainty. They might if the bet is purely monetary, as the payout for the less likely (the 10 percent) outcome might be considered worth the risk. However, no-one in their right mind would do this if a human life is at stake. To put it differently, no sane person would not get on an aeroplane if it has a 90 percent chance of crashing or play Russian roulette using a gun with ten chambers loaded with nine bullets.
The only scenario that may tempt someone to take on such a bet would be if that person were terminally ill, with a matter of days or weeks remaining, and the payout was sufficiently large to provide for his or her family for the rest of their lives. But that is an extreme situation and not something that the average person is likely to take up.
And there is the legal approach, the balance of evidence proving beyond a reasonable doubt that global warming is real and that we are responsible. This basically boils down to the question of what is considered acceptable evidence. Do we limit it to the research in peer-reviewed scientific journals? Or do we expand our terms of reference and allow all manner of published material?
It is a tough call as much of the discussion would be obscured by the highly technical and mutli-disciplinary nature of the topic, way beyond the level of understanding of the average person in what would be the jury for deciding the matter.
Another approach, and the subject of this article, is one from a risk management viewpoint. This is succinctly discussed by Greg Craven in his book and video "What's The Worst That Could Happen?". This effectively takes the discussion of whether global warming is real or not out of the equation. Or the scorecard.
So much of the discussion on the reality of global warming has lost objectivity, becoming polarized along poltical lines, that many people cannot see the forest for the trees. It is important to take a step back and that is the message that Craven puts forward so well.
The transcript of his video is in the link to his video. To paraphrase, Craven suggests that we think of the policy debate as a 2 by 2 grid (meaning that there are four squares in the grid). The rows (or y axis for the mathematically minded) is the question of whether global warming is true or false. The columns (or x axis) is whether we do something. For each of the four boxes in the grid, representing the available combinations, we ask the question, "What's the worst that could happen?"
Global warming is not real and we do something
The worst case is that policy action costs trillions of dollars and sends the global economy into a meltdown that makes the Great Depression of the 1930s look like going without pizza for a week. There are massive job losses, share markets nosedive and corporate failure occures at an unprecedented level.
It is a dire outcome, however the global economy would gradually recover. It might take years or decades, but life would eventually continue as we know it.
Global warming is not real and we do nothing
Big smiley face. Eventually, we will have to deal with the looming issue of peak oil, but for all intents and purposes, life goes on as normal.
Global warming is real and we do something
Big smiley face. If the scientists are right with their projections of the future, we have averted tragedy and we've addressed the looming issue of peak oil, putting the global economy on a path which moves it away from reliance on fossil fuels for its energy needs.
Global warming is real and we do nothing
The worst case, given that we used the worst case in the 'not real' case, is that we face an increase in the global thermostat in the order of 6 degrees over the next century. If the scientists are right, this means a rise in global sea levels that would see low lying countries submerged; desertification of vast areas of the globe, with its consequent impact on food production, water availability; increasing extreme weather events (drought, wildfires, more powerful hurricanes, floods etc) and ocean acidification and its consequent effects on marine fauna and flora.
Effectively, the world becomes a place that pre-dates human existence and effectively changes the planet. Scientsts suggest that worst case (6 degrees or greater) is likely to trigger mass extinctions. Human beings should survive, however the global population is very likely to be significantly reduced.
Can we live with each of the four scenarios?
Two of those outcomes are fine. The first is going to be unpleasant, however eventually things would improve and life would go on as normal. The last situation is the clincher. If that occurs, it is game over and, under a risk management approach, that is the one to be avoided at all costs. That only occurs if we do nothing.
The scorecard at the moment seems to be obsessed with the rows, the issue of whether global warming is real. From a risk management perspective this is largely superfluous. Shifting the paradigm to the columns, it becomes a question of whether or not we act.
We need to take a step back and understand the worst that could happen and that change in thinking makes it clear that the only sensible approach is to take action. And that means whatever action is necessary to avoid the worst possible outcome that could occur if global warming is real and we do nothing.
The scorecard so far on that policy response is not looking good. Yes, Copenhagen is still a few months away, but the general vibe is that a global agreement on the reduction in greenhouse gas emissions necessary to restrict global warming to less than 2 degrees Celsius by 2100 (which will still have consequences, but hopefully avoid the worst case ones) is unlikely to happen.
Politicians need to start considering the issue beyond their own short term political aspirations and ideological affiliations and ask themselves, "What's the worst that could happen?" This is a scorecard for a game that we really do need to win.