Friday, February 26, 2010
I found this here, and it saved me the trouble of making my own version. The "Marker" scenarios in the darker blue zone (or a subset of them actually) are what the IPCC studied as possible emission scenarios that were used to drive model-based estimates of what would happen to the climate over the 21st century. As you can see, the burst up due to the rapid growth of Chinese emissions in the 'oughts' has started to drive the actuals higher than any scenario that was studied.
You can get more details of the scenarios here.
In the short term it probably doesn't make much, if any, difference because there's so much lag in the climate system anyway because of the huge heat capacity of the oceans. In the longer term, it's likely to make for a heck of a lot more climate change.
Just to back up that last point a little bit, here's the left hand half of Fig 10.4 of the IPCC Fourth Assessment Report, showing the rise in global average temperature over the twenty-first century. The heavy lines are the average of a number of models (the numbers 17, 21, etc are how many models were used), and the light shading represents one standard deviation in the annual means of the various model runs. The colors represent various emissions scenarios.
So this is humanity's best guess about the impacts of climate change, and you can see that what we do now doesn't have a huge important impact on the temperature mid-century (which is going up quite a bit regardless in any reasonably likely scenario). But by 2100, the fact that we appear, at least for the moment, to be under a "worse than any of them" emissions scenario, will probably have a big impact if it continues.
Again in the 2046-2065 panel, the result is not terribly dependent on the emissions scenario, but by 2080-2099 it is. So, at least to the extent the climatologists have really understood all the relevant dynamics of the system, it appears that our children's world is already largely set, and we are deciding our grandchildren's climate.
Or to put it another way, the fact that our children will face an unstable climate is largely the fault of those of us in the developed world, but the fact that our grandchildren will face an even more unstable climate will be mainly due to the fact that China, etc, have decided to copy us.