The New York Times offers this brief, but useful summary of some of the evidence for human-caused glboal warming. Since it now seems incontrovertible that the planet is, indeed, warming up, the right-wing line has shifted to a rejection of humanity's role in the trend. I suspect as more data comes in, this line will prove untenable as well:
In the panel's last report, issued in 2001, and in more recent studies reviewed for the coming report, various trends provide clues that human activity, rather than natural phenomena, probably caused most of the recent warming. A number of trends have been identified:
- The global average minimum nighttime temperature has risen. (This is unlikely to be caused by some variability in the sun, for example, and appears linked to the greenhouse gases that hold in heat radiating from the earth's surface, even after the sun has gone down.)
- The stratosphere, high above the earth's surface, has cooled, which is an expected outcome of having more heat trapped by the gases closer to the surface, in the troposphere. (Scientists say that variations in the sun's output, for example, would instead cause similar trends in the two atmospheric layers instead of opposite ones.)
- There has been a parallel warming trend over land and oceans. (In other words, the increase in the amount of heat-trapping asphalt cannot be the only culprit.)
When you're done reading that, you can have a look at this companion piece about how warming has resulted in new islands appearing off the coast of Greenland:
All over Greenland and the Arctic, rising temperatures are not simply melting ice; they are changing the very geography of coastlines. Nunataks -- “lonely mountains” in Inuit -- that were encased in the margins of Greenland's ice sheet are being freed of their age-old bonds, exposing a new chain of islands, and a new opportunity for Arctic explorers to write their names on the landscape.
“We are already in a new era of geography,” said the Arctic explorer Will Steger. "This phenomenon -- of an island all of a sudden appearing out of nowhere and the ice melting around it -- is a real common phenomenon now.”
So, in your opinion, how long before we see the rise of Ictho Sapiens?
I don't know when, but it's obviously coming!
It seems to me that a critical part of the"human factor' part of the debate is: what % of the greenhouse gases in the atmosphere are anthropogenic. Almost no one seems to be raising this question, let alone answering it. I finlly found a website that presented detailed percentages of various gases. Here it is:
The answer seems to be <1%. Is this enough to say human activity is a significant factor?
That is not an useful question to ask. Put it simply - there is always a great deal of natural greenhouse gases in the atmosphere. The greenhouse effect is not just responsible for global warming, but also for raising the surface temperature of the Earth by a great amount from what it would be normally. Additionally, we have a number of gases like water vapour that, whilst having a large greenhouse effect, settle quickly into equilibrium (e.g. by raining the excess), and hence act as amplifiers or dampeners.
The actual useful question is how much of the temperature *forcing* is due to mankind.
For this, we have http://www.meteor.iastate.edu/gccourse/gwpotential/images/graph2.jpg
As for how much of that increase in CO^2 is due to us, we have this graph
showing that CO^2 levels have at least doubled over what we would expect from normal cycles. Added to that, we have the observations that the oceans are currently acting as carbon sinks, suggesting that our contribution is even higher than atmospheric measurements would suggest.
I'm very sorry for Darren and Craig of grades 7 and 8, but I think their data and presentation is... rather poor.
I noticed that the graphs in the NYT article started at 1900.
Are there any reliable sources for earlier data, either measurements or best estimates?
Basing conclusions on the period 1900-2000, relative to 4.5 billion years, is something like inferring the underlying machinery of the stock market from yesterday afternoon's charts.
Not that I'm arguing, or denying anyone's theory; I'm just looking for more information.