Quoting Bob Blakely <[EMAIL PROTECTED]>: > I'm not necessarily right, Jostein, this is just my best take on global > warming with a little (but by no means exhaustive) backup.
Bob, I apologise for being harsh. I guess I should have considered your reply to Dag more in light of the subject line. I guess it was the "who told you..." questions. Now, I'm not necessarily right either, but i'd love to share the thoughts I have, and the information I gathered, while I was still in the ecology trade. Since this _is_ off-topic, those of you not interested will do well to bail out now. I have a feeling this is going to get long... There are at least 3 gasses that contribute to the greenhouse effect. The most important is, as you said, water vapour. The abundance of water vapour in the atmosphere is basically dependent on the degree of evaporation, which in turn depends on temperature. Clouds do a particularly good job retaining heat in the atmosphere, and still allows much of the solar radiation down to the surface. One key question wrt the greenhouse effect of water vapour is whether it regulates itself by purely meteorological mechanisms or if other factors influence it as well. Airplane traffic has been pointed out, but the effect is thought to be small. One controversial theory is that cloud formation is influenced by cosmic radiation that rains into the atmosphere all the time. Cosmic radiation is in turn dependent on the solar wind, which varies with sunspot activity. Intriguingly, the lowest levels of sunspot activity ever recorded (around 1850) coincided with a period of harsh winters and cold summers. This is controversial, but if this theory is right, our CO2 emissions has probably much less to say than we have been lead to believe. The second most important gas is CO2. The numbers Bob mentioned is correct, afaik, and most of his arguments has been voiced before. 3% increase over 150 years seems like a small drop in the ocean, but the problem is; we don't really know how much change is needed to tilt the balance. Also, it is suspected that the current rate of change is faster than any before, seen in a geological time frame. Another undertainty is that CO2 is water soluble, and the oceans can absorb quite a lot of it. OTOH, solubility goes down as water temperature increase... CO2 has also been claimed to be a limiting factor for growth in plants, but that's not really true. There's only a small group of plants, called the C4-plants, that can effectively use higher levels of CO2. Maize is one example. The third most important gas is methane. There's very little of it in the atmosphere, but molecule by molecule it gives 4 times more greenhouse effect than do CO2. Important sources of methane is biological decomposition in oxygen-free environments. The gut of cattle, elephants and other plant eaters is indeed a good example, as Bob W. pointed out. A bit unfair on the Masai people, though... Wetlands all over the world also generate a lot of methane. Rice fields are important because the rice plants use the roots to ventilate the soil of toxic substances like H2S, and let out soil-trapped methane as well. There are also _huge_ deposits of methane locked by permafrost in the marshlands of Siberia and Northern Canada, and locked by high pressure in the depths of the large oceans. In the "disaster-scenarios" envisioned by the climatologists, the key variable is always CO2. The questions they try to answer is "what will happen to the climate if CO2 change?" The current consensus is that the most likely scenario is an overall increase in global temperature, but the total effect is much debated. One worst-case scenario is that the greenhouse effect from CO2 will alter the sea currents enough to let loose the marine deposits of methane, which will accelerate the process and in turn thaw enough permafrost to unleash the methane locked up in the arctic bogs. Increased temperature from the effect of CO2 and methane will increase evaporation from the seas, and thus the amount of water vapour and cloud cover, further accelerating the process. If, otoh, the sea currents change so that the arctic regions receive less heat rather than more, the outcome may be colder polar regions, and the onset of a new ice age because precipitation come as snow. As you see, if you have bothered to read me this far, the factors are complicated and predictions are fraught with uncertainty. We can be sceptical to the political correctness of crying wolf, but there is one good point in favour: We would err on the safe side, as Mike said. oh, well. A long rant... Thanks for reading. Cheers, Jostein ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.
