The temperature increase everyone likes to freak out about is only .5 - 1 degree over the past 100 years.
The amount of temp rise is correct but the span of time is another issue. You correct in using the span of 100 years but the actual rise has been recorded over the past 20 years although to be acurate there was a spike in temps in the late 1930's and early 1940's. Other than that the mean temp has remained below the average meanline.
http://www.grida.no/climate/ipcc_tar/wg1/figspm-1.htm
This is from the UN's Intergovernmental Panel on Climate Change so I hope it meet's his criteria of scientific foundation. The IPCC also shared the 2007' Nobel Prize with Al Gore for it's work on Climate conditions.
Another effect that has gotten more and more press has to do with the sun itself. Some have suggested the sun is getting hotter and to further that point, they suggest looking our our neighbors within our own solar system to see what is happening there. Good idea, let's do that.
What's happening on Mars?
http://news.nationalgeographic.com/news/2007/02/070228-mars-warming.html
What about Pluto?
http://web.mit.edu/newsoffice/2002/pluto.html
Hints of Climate Change on Jupiter!
http://www.space.com/scienceastronomy/060504_red_jr.html
Global Warming on Neptune's Moon Triton.
http://web.mit.edu/newsoffice/1998/triton.html
All have evidence suggesting a warming effect but all 4 have one thing in common. No people. But let's look further into this area of solar effect as it relates to earth and see what other ideas are brewing. As to solar radiation itself, not a purely scientific source but you can research the data for support but here's a trendline over 30 years pertaining to solar activity.
http://upload.wikimedia.org/wikipedia/commons/0/0d/Solar-cycle-data.png
What about the concept of "Orbital Forcing"? This one I happen to find interesting because not only is there a solar connection so to speak but it also has a completely natural CO2 release effect totally apart from human activity. Yeah, nature I'm surprised to learn has her own way of getting up in the middle of a very cold night and bumping up the thermostat so to speak to warm things up for in the morning.
Orbital Forcing is a concept that the earth's axis and orbit over time is in a state of change and that this change has a collective effect known as the Milankovitch cycles that effect climate. It is also strongly believed this effect leads to natural CO2 releases ahead of ice ages that IMO would suggest the natural process of ice and glacial movements throughout the history of our planet. If we have annual seasonal changes of spring, summer, winter and fall over the span of a solar year, IMO it's not hard to accept other patterns of hot and cold stretched out over vast amounts of time. There is some evidence to suggest the summer is now about 4 days longer than winter and spring is about 2 days longer than fall and some people think oribital forcing or rather the Milankovitch cycle is playing an effect.
As to natural CO2 releases there is evidence of this with the Vistok Ice Core in Antarctica going back 400k years in sutdies of ice core samples there.
For starters this article has some interesting data:
http://www.daviesand.com/Choices/Precautionary_Planning/New_Data/
However, in keeping with Jones good idea of trying to maintain purely scienctific sources, consider these links:
https://web.archive.org/web/20080512092938/http://cdiac.ornl.gov/trends/co2/vostok.htm
Graphics from the above showing CO2 levels over the 400k year cycle
http://cdiac.ornl.gov/trends/co2/graphics/vostok.co2.gif
As to temperture comparisions:
http://cdiac.ornl.gov/trends/temp/vostok/jouz_tem.htm
Trend graphics of temp.
http://cdiac.ornl.gov/trends/temp/vostok/graphics/tempplot5.gif
Other sources of data on this:
http://www.ncdc.noaa.gov/paleo/icecore/antarctica/vostok/vostok.html
I'll let you decipher through the tons of data instead of posting and commenting here as you all think my posts are to long anyway
and there is tons of good data to consider.
Although not a pure scientific source someone took the data from Vostok and combined it into a graphic comparing temp./CO2 levels and dust(particulate material)levels on the same graph over the 400k year study cycle.
http://upload.wikimedia.org/wikipedia/commons/c/c2/Vostok-ice-core-petit.png
As to ice levels I found this unscientific source as it pertains to ice volumes over the same 400k year period.
http://upload.wikimedia.org/wikipedia/commons/friend/f8/Ice_Age_Temperature.png
As I've read other scientific data IMO is does correlate to scientic fact but that's JMO based on my own reading of the data. I thnk like myself you'll notice a trend as it pertains to ice volume that surprisingly fits into the other trends of natural CO2 increases and temp increases. Are we just inside a natural trend of Mother Nature and happen to be heading towards a natural peak in the cycle?
I guess by now like myself you will have noticed the same trending patterns over time as I have but it would appear that CO2 levels do have a rise and fall cycle to them as well as ice volumes and none of the other cycle peaks based on using our Human condition today as a comparative have a "Human Factor Cause and Effect" to it. It would seem to suggest that nature itself has a common cycle in relation to CO2, temp and ice volume cycles all on her own but this time in our history we do have the human effect factor. I don't think at this point anyone can truly project over the longhaul if this human factor will be any effect, a positive or a negative.
Now am I suggesting throw caution to the wind and do what we want? OH HELL NO! We have no idea or data to show what our effect in this mix will have. It could be a drop in the bucket in the big scheme of things but it could just as well make a bad situation worse and the fear is once in it, the conclusion could be horribly bad and reversing the ill effects a longterm process with the worse being no reversal at all. Most I've seen believe a long reversal process if it goes critical mass.
Western civilization in expanding it's own economic systems as well advancing trade and democratic societies have moved what were previously undeveloped countires into modern industrial societies with some becoming giants like China and India. Imagine a moment adding those billions of people into the mix of living as we do in the west with all having cars, stereos, TV's, gas grills and the list goes on. What effect does this have on the whole climate picture? What about the amount of land needed to be cleared of trees that consume CO2 and expel O2 and replace with homes and building for business to sustain the economics. Or the land needed to grow crops to feed these new centralized industrial armies of advancing societies?
That is the big question and really IMO at the heart of the debate but at the same time there is IMO no clear cut answer either!