G'day all,
One parting post.
A thread about climate that most interested me, the flips between glaciations and interglacial periods and the time they took. 3 years!
Well actually there is evidence that suggests it might have been seven but centuries ... huh!
It takes centuries for 2 km thick ice sheets to melt but very little time at all to switch from vast areas that are covered by snow 9 or 10 months of the year to be snow free year round. And the evidence was available in the 70s that it took between three and seven years for the last glaciation to end. It was just very hard to find. Since then, ocean sediments have re-inforced the very rapid change.
But a change from an interglacial period to a hotter one? That's something that has not occurred in this Ice Age (ie for the last 3 million years). Would this be rapid? Well it would depend if you thought the two were different states of relatively stable self-correcting climate conditions.
Interglacial periods seem to be self limiting. Glacial periods not so much so. That might explain why for the past three million years, all but a few thousand have been glaciations rather than interglacial periods. It would be really good to this discussion if anyone knew why the flips occur in the first place but as far as I know, no one does.
So what limits interglacial periods from getting much hotter than we have now? If it gets hotter, you get much greater evaporation. Not at the tropics which do not change much at all, but at the near tropics and mid latitudes. This is one of the big questions about CO2 and just what it does as a greenhouse gas. Water vapour is a greenhouse gas but it can also make the whole planet much colder if there is too much of it in the air.
More heat, more evaporation, more water vapour, more clouds. The question is what type of clouds? Are they going to be reflective or absorb heat? I wouldn't have a clue and since this is the least understood area of climate, no one else does either. But one thing is certain, if you added say 2 degrees Celcius to the earth's temperature you will raise sea levels by somewhere around 12 metres. You then have the problem that plate techtonics says that more weight over a plate and some of it "pops" up in compensation. So you don't really get 12 metre increases. But you get somewhere around that. That is not the same as the doomsday predictions of sea level rises of as much as 500 metres (yes, I've seen a prediction with that really stupid figure on the front page of a major newspaper - and not the National Enquirer type either).
So 12 metres is it. No matter how much you melt, that's as far as you can go with the continents and land masses we currently have. This has a huge effect on evaporation and it will rain much more in a great many areas. Do you think this will cause drought? I believe it would, in some places. But overall, because of the spread of continents, the arable land area would go through the roof, mostly in third world countries.
So, starving because of it getting warmer? Hardly.
Of course, all of this pre-supposes that the warming is not some "tipping point" that results in a runaway warming of the earth. If you really want to scare people, and it would appear that there are many that do, then you compare our current situation with Venus, and suggest that the world would just keep getting warmer until the water boiled off the earth. Of course, this goes against everything we understand about climate variation over the entire history of THIS planet, but, hey, we're trying to scare people into doing the right thing. Global warming is going to destroy the earth. So what if we lie about what might happen so we can get some action. The last couple of lines were sarcasm by the way.
With that I take my leave. Adios.
Richard
