(March 16, 2009 at 5:40 am)Darwinian Wrote: Before I can fully accept the possibility of Man Made global warming there are a few inconvenient facts that first need to be cleared up..
The main two that spring to mind are these..
Firstly, as I understand it, Humanity is responsible for emitting about 6 gigatonnes of CO2 into the atmosphere every year.
This sounds like a huge amount but when you consider that normal volcanic activity is responsible for approx 150 gigatonnes then it seems that we have a very long way to go to even come close to matching nature.
Secondly, the fact that the records for the Greenland ice sheet over the past hundred thousand years or so consistently show that it is always the temperature that rises first and then some time later, sometimes years, the CO2 starts to rise as well..
I would have though then that if CO2 was responsible for global warming it should be the other way around.
The idea is of a carbon cycle whereby carbon dioxide is transferred between several resevoirs (i.e. atmosphere, biomass, oceans).
Ice core data shows that for several thousand years before the Industrial Revolution, atmospheric carbon dioxide was constant at 280±10ppm (parts per million) [1] , and therefore the exchange between resevoirs was constant.
Since the start of the industrial revolution, atmospheric carbon dioxide levels have risen to ~377ppm.
To me this is pretty good evidence that we are increasing atmospheric carbon dioxide substantially.
To explain how an output that is ~5% of that output by volcanic activities (according to your figures of 6 and 150 GT) I came up with the following analogy:
Imagine a waste water processing plant that can process 1000L of waste pumped into it per day.
Now imagine that it does process at full capacity (that is, same amount going in as going out; this represents the pre-industrial equilibrium between resevoirs).
There are four sources of waste, each contributing 250L of waste per day.
Imagine one of these is a company that has found a way to increase their production, and the new method increases their daily waste output by 1L/day.
They think "well, the extra 1L we want to pump to the processing station is negligible copmpared to the 1000 it already processes".
This maybe true, but the waste is still coming in faster than it can be processed, the equilibrium has been disturbed, so there must be a build up somewhere.
As for your second incovenience, I thought the error bars on the data made it impossible to say whether temperature rises or atmos. CO2 increases came first :S
Could you give a link to the data/paper you're referring to?
I think the evidence for "man-made" global warming is reasonable and says it is feasible, and the relevant physics that we currently understood well provide a good theoretical basis.
However, the earth's atmosphere (in terms of weather, temperature, radiative forcing etc) is an extremely complex system and the only way to really make any predictions is to bang your model onto a supercomputer. Current models are inaccurate at best, there need to be a lot of adjustments and refinements made before we understand the earth's climate well.
What do people think of a kind of environmental Pascal's wager?
[1] Climate change 2001, the scientific basis (Cambridge University Press, 2001)
Galileo was a man of science oppressed by the irrational and superstitious. Today, he is used by the irrational and superstitious who claim they are being oppressed by science - Mark Crislip
