quote:
Originally posted by Sarah77:
I suppose that there are some of you on here who have actually carried out experiements based on the carbon cycle and so on.
I was wondering if anyone would be game enough to be able to list. YES list!! The complete list of variables someone would need to include in their study to calculate the 'supposed' reasons for climate change. This should give us some idea of the vast calculation that scientists are trying to make here.
Of course the obvious source of heat is the SUN and without it we would be a dead planet, and without the greenhouse effect we would not be able to survive either and as the programme stated..
Here is my list, in my unscientific mind these are the Variables I believe should be included.
Sun:Intensity/Heat of, number of sun spots, solar flares??
Water Vapour
Cloud density??/coverage
Absorption of heat by the earth, buildings, animals, people, oceans & seas etc etc
Absorption rate of co2 by plants, sea
Amounts of CO2 dispersed by sea, people, animals, sea, rotting plant-life
Other percentages of gases in atmosphere....
Heat generated by people, animals, fires/production plants which have a prolonged effect on the atmosphere...
Please feel free to pick me to pieces..
Hi Sarah,
Let me first of all say, while I have a scientific training I'm not a climate science specialist - I just try to keep up with what's going on in the field.
Your list seems like a good start, you've covered several important factors -- but you won't be surprised to know that there are a number of other factors which have some effect on global temperature and climate.
I'll leave the task of giving you a complete list to someone better qualified... but here are some factors that spring to mind:
1. Milankovitch cycles are the the mechanism now understood to cause ice-ages. The eccentricity, axial tilt, and precession of the Earth's orbit all vary in several patterns; these effect the amount of solar radiation absorbed by the earth atmosphere - resulting in the 100,000 year ice age cycles that the Earth has experienced over the last few million years.
Incidentally, you may remember the graph shown in "Swindle", where there was shown to be an 800 year time lag between CO2 levels in ice-cores lagged and the estimated average global temperature. This is because these graphs show vast periods of time; on this scale, the Milankovitch mechanism is the primary factor driving temperature change (and the changes are huge!). The transition to an inter-glacial warm period (we're in one now!) has an effect on the natural carbon cycle, gradually releasing more CO2 into the air.
Obviously, this doesn't prove that increases in CO2 have NO EFFECT on temperature, as was claimed in the program! It just means that in the long run, the Milakovich effect is bigger.
2. Aerosol pollutants (i.e., tiny particles come out of dirty industrial chimneys etc). The huge increase in this kind of pollution in the post war period produced, in effect, a thin layer of high altitude smog around the northern hemisphere - which reflected some solar radiation back into space. The effect is called "Global Dimming" - and is believed to explain the steady DROP in everage global temperatures between about 1950 and 1980. In the 70s and 80s, most industrial contries introduced "clean air" laws -- and when the pollution levels dropped, the cooling trend stopped -- and the global temperatre graph resumed the overall warming trend that's been apparent for most of the past century.
You'll remember that the temperature graph in "Swindle" showed the 1940s-1980 cooling period. It was suggested that this contradicted the view that CO2 raises temperatures.
3. Carbon sinks. When scientists first calculated the amount of CO2 we release into the atmosphere through burning fossil fuels, and calculated the effects this should have on temperature, they encountered a puzzle. Temperatures were rising - but much less than the calculations predicted! It was soon realised that this was due to various natural mechanisms which take CO2 out of the atmosphere. These include absorption of CO2 in the oceans, the growth of forests, the burial of vegetation in peat bogs etc. etc. When these factors are taken into account, the calculation fits the data much more closely.
4. Feedback effects. On of the long-term hazards of Global Warming is the possibility that increased temperatures could cause carbon sinks to rapidly release their carbon into the atmosphere -- either as CO2 or much worse, as methane (which is a much more powerful greenhouse gas). For instance, hotter temperatures in the tropics and a longer dry season causes more forest fires (releasing C02); hotter oceans are more likely to release methane, from deposits on the ocean bed; melting of the artic tundras will release still more. Its not yet clear exactly how much hotter it needs to get before these mechanisms kick in; current estimates are around the 3-5 degree mark. I just hope we don't have to see it happen, in order to find out!
4. Agriculture. Everyone goes on about fossil fuels, but a huge amount of greenhouse gas is produced on the world's farms. Rice paddies are a major source of methane -- and all the world's livestock, especially cows, produce vast quantities of the stuff. If we all went vegetarian, we'd reduce our greenhouse gas emissions by a huge amount. (Not quite sure of the relative figures here -- but suffice to say, its a significant factor).
Hope this helps.
* Free-thinking does not just mean choosing to believe whatever makes you feel good. There's no thought at all in that. *
I think that it's just too big a job and the others must have knackered themselves out...my brain hurts reading all that has been written!
