原帖由 pyling 於 2012-12-9 02:09 AM 發表
"it is still arguable whether the climate changes in last 100 years represent actual human activities influence after industrailization and city developments OR some natural longterm fluctuations ...
I only reply on the "causes" or "explanation" of the observed fact of global average warming as discussed. No doubt I agree that no matter the earth is warming or cooling and by whatever reasons, human activities have already done too much in too fast a rate to change many habitats on a global scale and that much stronger awareness and actions on conservation are needed long long ago.
We must separate theoretical explanation with practical conservation action. The latter should be done much earlier before full theoretical understanding, same as the case of biology vs medicine.
Global drastic or rapid changes, of whatever factors, will worsen any status quo, whereas any slow changes will be better adapted.
Interestingly, some changes attributed to global warming is of questionable detrimental effects, e.g. the more northerly and southerly extension of coral reefs, extension of certain fisheries like from the Atlantic to the North Sea. Even the recent appearance of anadromic gobies in some other places like Hong Kong as I suspected.
The earth's food supply problem, I think, is very complicated but it is more related to uncontrolled population, political, commercial, distribution and other human evils.
Habitat destruction contributes to climate change but the vice versa may not be in the same rate. Relatively rapid habitat destruction caused a chain of events adding to slow global temperature rise that in turn change physical and biological factors that in turn change or worsen the change in habitats.
As for your "reasoning", may I first clarify your points:
1. Average solar heat is relatively constant. Heat that cause rise in temperature should be carried mainly by long wavelength part of sunlight, i.e. infrared rather than the short wavelength ultraviolet, is that what you mean by "shortwave" and " longwave"? If yes your "shortwave" should not concern heat transfer as UV is not involved in solar heat transfer. The difference in temperature with and without sunlight, as maybe exemplified by the temperature difference in day and night time of deserts, or more drastically the front and back sides of the moon. So it is the sun's input of "longwave" and the earth's loss of "longwave" to outer space that is concerned with your "balance" right?
2. Greenhouse gases, basically carbon dioxide, is said to REFLECT rather than absorb heat. Its proposed that part of the heat that should have been lost to outer space was reflected back to the earth by carbon dioxide in the atmosphere causing temperature rise.
3. Yes, the Law of Conservation of Energy is assumed.
4. I would say over the last 100 years we see incoming solar heat > outgoing heat loss to outer space.
5. Yes, so in theory the global warming effect of carbon dioxide is lessen by the increase rate of heat loss due to increased temperature. However, I do not know how significant is this effect.
6. The balance sheet is simple on large average global scale. However, many smaller scale effects that affect our livelihoods need to incorporate many other factors, I may think of the solar cycle, solar wind and spots activities, earth's recent change in magnetic field or possible nearing the time of magnetic reverse, volcanic or seismic activities, oceanic current and the "conveyor belt" system, not to mention the many anthropogenic factors.
[ 本帖最後由 jasonpoon 於 2012-12-9 14:26 編輯