The Climate Bathtub

My first serious push into education about climate change came when I heard MIT's John Sterman share his research (with Linda Booth Sweeney) showing that many people harbor fundamental misunderstandings about the dynamics of the climate system. One of the most common misunderstandings they found was the expectation that CO2 levels in the atmosphere would stabilize if emissions were 'frozen' at current levels. This intuitive belief neglects the crucial information that CO2 is now being added to the atmosphere at more than twice the rate at which is is being removed. In other words, freezing emissions at current levels would mean that global society would continue to add twice as much CO2 each year as the planet was able to assimilate.

As the G8 leaders meet this week, unable to agree on even modest concerted action on climate change, this is a critical understanding every citizen deserves to have.

Now, inspired by Sterman and Booth Sweeney's research and via a project advised by them, climate change educators have a new tool at their disposal - a web-based simulator that shows the levels of CO2 in the atmosphere projected into the future under three different scenarios: business as usual, emissions freeze, and emissions reductions of more than 50% by 2070. The simulator uses the metaphor of a bathtub which is filled by CO2 emissions and drained by net removals.

I'd urge all of you climate change educators out there to give the tool a try in your presentations and trainings. If a picture is worth a thousands words, a simulation must be worth even more.

When I've heard John Sterman talk about the prevelance of this misunderstanding he frames it in terms of the education system not helping people comprehend rates (emissions and removals) that control the level of an accumulation. He may be right.

But I've been wondering lately if the misunderstanding isn't even deeper. We all know that over the long term you cannot fill a bath-tub twice as fast as it drains without the tub overflowing. Which leaves me wondering if the misunderstanding is not so much a problem with rates and accumulations as it is a problem with how we think about the atmosphere, something that appears to a casual observer as both static (we can't see the inflows and outflows) and endless (not finite, like a bathtub.)

Another possibility is that most people still do not know the simple fact that the climate bathtub is filling at more than twice the rate that it is draining; it maybe that this simple fact is lost in the complex way the climate story is reported.

The great thing about this simulator is that whatever the cause of the misunderstanding allowing people to experiment with this simple tool should help them sharpen their understanding of how the climate works and why we cannot wait to act.