Psychological Thresholds for Climate Change

The fact that the carbon dioxide in our atmosphere recently passed 400 parts per million (ppm) has been described as a “psychological milestone” (new scientist and slate.com) or an “important psychological barrier” (wired.co.uk). The idea is that moving past 400 ppm for the first time in human history would alarm the public. We all know that people don’t respond to numbers logically, and that not all increases are the same. Turning 40 is a bigger deal than turning 39. Paying $9.99 is different than paying $10.

So far, though, there hasn’t been much evidence of increased concern. Are psychological milestones so insignificant?

I think two things are going on here. One is that the mainstream media have not really played this up. You can’t react to something if you don’t know about it. The larger story of how mass media downplay climate change is a different question. (See this useful site at the Center for Science and Technology Policy Research.)

The second is that milestones loom through the windshield much larger than in the rearview mirror. Once you pass your 40th birthday (or your 30th, or your 50th) you notice that life is pretty much the same as it was during the previous week. Round numbers have significance in guiding our purchasing, but when we can’t do anything to prevent their occurrence they move toward us and then become the new normal. As we creep toward 410, 400 won’t sound so bad.

For changing behavior, goals are better than milestones. Emphasizing where we want to be – and how to get there – may be more important than a focus on where we are.