Sunday, July 8th 2012, 5:10 PM EDT
We’ve been told often enough that climate change is going to mean the disappearance of many or even most of the tropical forests. Something of a problem: although it seems that this might not be entirely true. At least one paper is arguing that an increase in CO2 will increase the size and land area of those tropical forests:
“Experimental studies have generally shown that plants do not show a large response to CO2 fertilisation. “However, most of these studies were conducted in northern ecosystems or on commercially important species” explains Steven Higgins, lead author of the study from the Biodiodversity and Climate Research Centre and Goethe-University. “In fact, only one experimental study has investigated how savanna plants will respond to changing CO2 concentrations and this study showed that savanna trees were essentially CO2-starved under pre-industrial CO2 concentrations, and that their growth really starts taking off at the CO2 concentrations we are currently experiencing.“
It’s seems a fair enough observation: if tree growth is currently being limited by atmospheric CO2 then more of it will increase tree growth. And the implication is that what is currently savanna will become forest: we might assume that what is currently grasslands will become savanna as well.
The point of noting this is not to then go on and say, well, climate change won’t be a problem so fire up those coal plants. It is, rather, to point to something really very worrying. We do not know, still do not know, what are all the feedbacks in the system. This leaves us uncertain about the effects of any particular rise in atmospheric CO2.
This is normally addressed on the up side: if we are more uncertain about how bad to appallingly bad the results will be then we should take more care, spend more now, to avoid emissions. But the opposite is also true and it is this opposite that is more rarely mentioned. If the result comes in below current expectations, if we are uncertain as to how little effect there will be, then we are wasting resources by attempting to limit emissions now. And given the way the world is at present the wasting of resources means that people die, right now. What we spend on windmills cannot be spent on vaccines for the diseases of the poor: just to use one obvious example.
I’m still not entirely sure where I am myself about climate change. If it is real then yes, I still argue that a carbon tax is the sole and complete solution. It is within that policy option that changes in the effects climate change move me around. There are, essentially, two options. The Stern Review one, an $80 a tonne CO2 tax now and the Nordhaus much lower tax now rising to much higher levels (say, $250) in four decades time. The more uncertain about the low end we are the more I veer to the Nordhaus solution: for it’s very much closer to an entirely no regrets policy.
For we’re going to replace pretty much all of civilisation’s infrastructure over those next four decades. There will be few extant power plants still operating then. So making sure that when we replace them we do so with ones that meet their carbon costs is a much cheaper option than insisting that all extant ones currently do so.
Oh, and as to there only being two such options: there is a third, Hansen’s. But his idea is really just Nordhaus’ with a very different number for the costs of carbon emissions. So different as to be entirely wrong in fact.