A $20 bill is consensus reality. The fact that it is worth $20 in goods and services is a fact only because we all agree it is worth $20. In different times and places, we may well have required a leaf of tobacco, a particular kind of stone, or a small bit of metal to complete the same transaction.
Changing consensus reality is a slow process. The notion of money as an electronic blip, allowing you to buy something at the mall by swiping a card, is not something one can spring on a population that only knows barter. The evolution from exchanging things for things to things for symbols of things is one that took centuries. The further evolution of those symbols from precious metal to mere pixels took centuries more.
Yet social progress is a matter of shifting consensus reality. Gradually. Money is just one of many bits of social reality that needs to be negotiated, debated, and agreed to in order for modern economies and cultures to work. Given that things like money and traffic laws pretty much require the cooperation of everyone, consensus reality moves very slowly.
This brings me to climate change. It has taken us a couple of centuries to agree that the basis of society is shared consumption and production. Now, climate change suggests that a key ingredient in that worldview - affordable oil - might actually require us to rethink that model. This is problematic, to say the least.
Changing consensus reality is a slow process unless a community is in crisis. A crisis has a way of creating new consensus very quickly. "We're under attack!" is a claim that can be quickly verified and acted on.
One of the problems with climate change is that it is abstract, slow moving, and there is a long delay between when carbon is pumped into the atmosphere and when we experience the effects. I can't think of any examples in history of communities adjusting to such threats in advance.
Imagine (he wrote, using an example from some source long forgotten) that you have a pond with a lily pad problem. The surface covered by the lilies is doubling every day and, experts tell you, the entire pond will be covered by the end of the month. 31 days from the time that the lilies are first introduced and the time that they completely cover the pond. It will not be until day 24 that even 1% of the pond is covered. Even on day 29 - just two days away from the time when the pond is completely covered - the pond is only 25% covered. If, on day 30, you decide that there might be something to the forecast that so alarmed your expert, you're still only dealing with 50% coverage. Worse, you have only one day in which to do something.
This seems to me one of the most important issues to face us. How do we build consensus around reality that is, as yet, still abstract, and still mere possibility? Terrorists grabbing hold of Russia's atomic arsenal? Pandemics that kill one-third of the population? Collapse in the world's financial system or information systems or electrical or water or transportation systems? Proof that these issues are real issues will come too late.