July 19, 2002
You can view Sterman and Booth Sweeney’s full study results here
Recent Bush administration statements on climate change just do not add up. Our president and his advisers keep talking about climate as though we can wait for overwhelming signs of trouble and then switch our course in time, but the climate system is notoriously slow to respond to our policies. The Bush administration talks as though we are driving a sports car, when really we are steering an ocean liner.
For example, last week White House science adviser John Marburger briefed a Senate Panel on climate change, saying, “We know we have to make very large changes if this turns out to be a problem. The consequences of human-induced global warming could be quite severe.” (7/10/02)
Yet at the same briefing the Administration stood behind its “wait and see” policy: we should only “slow the growth of greenhouse gas emissions (GHGs), and – as the science justifies – stop, and then reverse that growth.” (G. Bush, 2/14/02)
Climate change could be severe and yet we should wait before acting. How can one reconcile these two statements?
MIT professor John Sterman and Harvard’s Linda Booth Sweeney explain how this “wait and see” approach feels right if you expect the climate to be a non-delayed, responsive system – one that handles like a sports car. Their recent experiments confirm that many mathematically and scientifically competent people see climate behaving much this way. The majority of their student subjects predicted that if humans reduced emissions of GHGs, the storehouse of GHGs in the atmosphere and global temperature would promptly decline, roughly following emissions.
However, Sterman and Booth Sweeney explain that the climate system actually has significant delays. They suggest we think of GHGs in the atmosphere as water in a bathtub. The more water, the more the gasses trap heat and contribute to warming; less water, less warming. The faucet filling the tub is global emission of GHGs, primarily from burning fossil fuels. The drain is the removal of GHGs as they are taken up by plants and absorbed into the oceans.
Right now the tub is the fullest it has been in 420,000 years and the water flowing in is about double the rate of what is flowing out the drain. In order for us to lower the level of the water, we will need to reduce the inflow first by half to match the outflow, and then by more to begin to reduce the level of water.
The bottom line of the “bathtub perspective” is this – if we “stopped and reversed” the growth of emissions, it could take many decades to actually reduce global temperature.
If we believe Mr. Marburger that climate change could be bad, we need insurance to cover that possibility. The Bush administration’s insurance plan – reducing emissions once we confirm negative effects – is a sports car kind of plan. It’s a plan that assumes rapid response and great steering, but it is not the kind of plan that can work with a slow-responding system.
The more prudent insurance plan is to go even further than the Kyoto accord and reduce GHG emissions below the rate of absorption and do it before we see negative effects in full force. This will not be easy, technologically, culturally, or politically. But it has to be easier than steering an ocean liner while expecting it to respond like a sports car.