Here is my $0.02 cents on global warming. While my estimates are on the conservative side (mean warming of 1.5-2C in the next 100 years), however the rises in temperatures will not be gradual but rather sudden. I think in 1998 we went through one, as a result much needed winter rainfall in Southern Australia has decreased by 20%, which is a factor behind the worst drought in recorded history we are experiencing here.
This 4T coming up will have this as a major issues.
Humans have had an impact on the global greenhouse emissions since the beginnings of agriculture, the clearing of forests for grazing, the planting of crops and the methane coming from livestock. Probably resulted in temperatures in the last few thousand years being a little higher than they have should be.
http://www.smh.com.au/articles/2003/...732281706.html Since the industral revolution Co2 levels have risen from 280 parts per million to 370-380 parts per million, a more than 35% increase. Given the rise in Co2 levels in the amosphere the warming should have been more than 0.6C mean recorded globally since 1850. There is a thing called global dimming, which is caused by aerosols being poured into the amosphere as a result of industry, which reflected sunlight and limited the extent of warming caused by rising Co2 levels. The level of aerosols have decreased in the developed world, could be rising in the fast industralising countries like China and India although.
If we contiude business as usual in regard to greenhouse emissions, globally temperatures will warm to levels which were seen 120,000 years ago during the last intergalacial. When temperatures globally were 1-2C warmer than today. Back then sea levels were 5-8 meters higher than today, forests grew as far north as North Cape, Norway which is now Tundra, trees like Oak and Hazel grew as far north as Oulu in Finland which is at 65N. Also the forest-priare boundary was where Fort Lubbock, Texas is today, instead of Dallas.
http://en.wikipedia.org/wiki/Eemian_interglacial I dunno if the climate modern similar to the Pilocene period around 5-2 million years ago would be apporiate because back then the straits of panama, allowed the gulf stream to go into the arctic ocean because the ocean salinity levels were lower. That would have resulted in huge temperature increases in North America, Northern Eurasia, plus a stronger monsoon in Africa and Eurasia, meaning the Arctic ocean was ice free in summer, Greenland was tundra and boreal forest, the sahara and arabian deserts were grasslands and trees grew right up to the arctic ocean.
Overall I think global greenhouse levels will reach to around 560 parts per million, literally a doubling since the beginning of the industral age. That is given a business as usual approach, greenhouse emissions will peak once the all the countries of the world become economically developed as western countries are now.
For example a Co2 level some 100 parts per million lower than pre-industral levels, maybe resulted in temperatures globally 5C cooler than present, however the milankovitch cycle where the earth's axis shifts, which is linked to glacial and interglacial contributed greatly to those lower temperatures.
My rough estimate is as co2 levels in the amosphere reach levels double pre-industral levels, mean global temperatures will rise by 1.5 to 2C. But the effects will be not evenly distrubted in North America temperatures will rise by 3-4C on average. Boston would have a climate like Baltimore, some places will get wetter, some places will get drier.
A sudden warming of the earth's climate would be a disaster, because global agriculture depends on a stable climate and if the climate patterns were to suddenly shift, some places will face ruin and until the agricultural zones of the world shift, agricultural yeilds will crash.
This is quite potentially scary stuff, greenhouse emissions must be reduced post haste to avoid these things from happening, however we have to develop ways of reducing greenhouse emissions which do not reduce living standards or economic growth.
I'm in favor of widespread use of nuclear power (replacing fossil fuels), diverting of subsides for fossil to subsides for cleaner forms of energy like solar, nuclear fission and fusion, wind and compressed air engines (which run on electricity).
