theyeti

They are. The current thinking is that <a href="http://www.ngdc.noaa.gov/paleo/milankovitch.html" target="_blank">Milankovitch</a> cycles, which are changes in the Earth's wobble every 100,000 years, are the "trigger" for the Ice Ages. However, the increased or decreased solar radiation from the Milankovitch cycle is not enough to account for the temperature increase/decrease. It's thought that initial changes in temperature, or accentuations of seasonal variation, will release or sequester CO2 such that the effects are greatly amplified. Read more about it <a href="http://www.newscientist.com/hottopics/climate/climate.jsp?id=22354400" target="_blank">here</a>. Contrary to what some will tell you, we're still on the "up swing" of the cycle. We are not expected to enter the "cooling" phase of the Milankovitch cycle for another 25,000 years or so. There are other orbital variations and cycles, and we may (or may not, I don't know) be entering a "cooling phase" in one of those, but the Earth is not expected to receive a net cooling effect because of them.
Well, I suppose this is answered above. There is a lot we don't know about these cyclical changes, but we do know that the current warming trend cannot be explained by them. We also know that CO2 and other greenhouse gases do trap heat, and so there is a causal relationship between their concentration and temperature, not merely a correlation. Also, as you note, "abrupt" means about 5 or 10 thousand years. Not the two hundred years (1900-2100) that will have seen us experience a minimum of 2.0 degree C increase given our most accurate models. (The maximum of 6.4 degrees!).
Notice that CO2 levels have fluctuated between a low of around 200 ppm and a high of around 300 ppm for the last half million years. These 100 ppm or so additions take place over at least 10,000 years give or take, or abouth 0.01 ppm per year. In just 150 years, we have increased the CO2 level by about 80 ppm up to around 380, which makes for about 0.53 ppm per year. That's more than 50 times as fast, and it will continue to get faster for the foreseeable future. (Please note that these are my own back-of-the-envelope calculations based on the graphs; they're probably not the same as the "real" calculations done by pros, but the principle remains.)

So what we have is:
<ol type="1">[*]We are increasing atmospheric CO2 levels at a rate many times that of the natural rate.[*]We know that there is a causal relationship between CO2 and heat trapping.[*]We see a strong correlation between past CO2 levels and temperature, regardless of what time frame we're looking at.[*]The Earth has been heating up at an unprecedented rate in the last century, most of that in the last 30 years when CO2 emissions were highest.[/list=a]

IMO, there's nothing left to argue about as far as the reality of global warming is concerned. At this point, all we should be asking is 1) what's going to happen (i.e. how much warming and what will it do) and 2) what should we do about it.

theyeti

Late_Cretaceous

1) Is the earth warming up?

Most likely, but can the current warming trend be extrapolated into the future - and how far?

2) Are humans the primary cause?

A significant cause for sure. But it is not only CO2 emissions. Every mile of blacktop, ever acre of cleared forest, etc. is also affecting the climate.

3) Are the effects significant?

Any change is significant if your economy can't adapt

4) What should we do about it?

Adapt.

Splat

Um, 'fraid not. No environmental science issue has ever received as much scrutiny as has global climate change through the IPCC process and all of the related funding that's been thrown at it. It's the largest peer-reviewed effort ever undertaken, and I doubt that anybody involved in it would tell you that the results and conclusions are 100% ironclad. 90% or 98% maybe, but not 100%.

There are still uncertainties--the role of clouds and precipitation being among the biggest--and the current worst-case scenarios could be significantly ameliorated if there are negative feedbacks we've missed. Anybody (or group of anybodies) who Identifies such flaws will have their career(s) utterly made by doing so. That's the beauty of the system: iconoclasm is rewarded richly if it can be backed up.

(btw, Ehrlich is an entomologist, so it's hardly surprising that he was more wrong in his social predictions than were social scientists. Note that the IPCC involves social, as well as natural, scientists, which should improve its predictions on the society front.)

No need for that. You should be skeptical, but the failed predictions of some scientists on some issues 30 years ago isn't a good basis for skepticism on global warming now.

elwoodblues

Maybe 60%?

<a href="http://www.colby.edu/sts/controversy/pages/ipcc_controversy.htm" target="_blank">web page</a>

"The survey indicated that not only did 40 percent of the group not agree with the IPCC summary, but also, that many felt that the report was running into the danger of describing a false scenario to the public. Almost all of the IPCC group agreed with the basic conclusion stated on p 254 of the report that, "it is not possible to attribute all, or even a large part, of the observed global mean warming to the enhanced greenhouse effect on the basis of observational data currently available." "

I have major problems with the reports the IPCC has issued, largely because they seem to be shushing dissident voices from their own ranks, marginalizing or ignoring disagreements even between their own scientists. The IPCC has become too politicized to wholly trust it's impartiality.

Jesse

Here's an interesting chart I came across on <a href="http://www.ucsusa.org/environment/gw.science.html" target="_blank">Science of Global Warming</a>:

[ September 24, 2002: Message edited by: Jesse ]</p>

Ruy Lopez

Yeti, Lone Ranger or Jesse:
Can you help a computer illiterate? How does one post a chart, pictogram or picture with our message on the board. I only know how to edit, copy, and paste. Does not work with charts.

Thanks.

Jesse

demon-sword:
Can you help a computer illiterate? How does one post a chart, pictogram or picture with our message on the board. I only know how to edit, copy, and paste. Does not work with charts.

First you have to find the URL of the image--on internet explorer you can click on an image and a popup menu will come up with the option to "open image in new window", I think you can do something similar on other browsers. Then type something like this:

{IMG}http://www.yourimagehere.com{/IMG}

...except instead of using curly-brackets use square-brackets (replace "{" with "[" and "}" with "]")...I just typed it that way so the UBB software wouldn't think I was actually posting an image.

If you're still confused, to the left of the window for composing messages there's a link on <a href="http://iidb.org/ubb/ultimatebb.php?ubb=ubb_code_page" target="_blank">UBB code</a> which explains images and other stupid UBB tricks.

theyeti

Let's see what this statement is preceeded by:

First of all, I curious as to how a survey conducted in 1991 can tell you what people thought about the 1992 report. Ignoring that for now, this is talking about IPCC reports that are now a decade old! You simply can't overestimate how important the last ten years of data collection and refined models have become. Back in 1990, there was plenty of legitimate scientific skepticism about climate change, though it was in the minority. That skepticism has almost entirely evaporated by now. Why couldn't the author of this web page at least put up some info about the 2001 IPCC report, or failing that, at least the 1998 report? Just perusing aroung that site for awhile, I noticed them parading numerous myths that were debunked years ago.

Oh, and who is this SEPP being referred to, that supposedly conducted the survey? It's a conservative think tank started with funds from <a href="http://www.uow.edu.au/arts/sts/sbeder/ecologist.html#RTFToC2" target="_blank">Rev. Moon</a> (!) to discredit global warming and nearly every other environmental threat. Its director, Fred Singer, is rolling in money from the energy companies. He hasn't done any real reseach in 20 years; he just whores himself out to these so-called think tanks. Simply put, SEPP can't be trusted to tell you the time of day with any accuracy. Unfortunately, they are only one out of many propaganda groups with innocuous names deliberately spreading disinformation about climate change.

It is somewhat politicized, but in the opposite direction that you're implying. Numerous countries, especially from OPEC, have inserted language more cautionary than what the scientists thought was warranted. The climate change conspiracy theories that claim that a bunch of conspirators are trying to make climate change look real when it's not are simply stupid. Why would anyone from the government want to exaggerate the threat? I can see environmentalists doing it, but government officials from all over the world? The fact is, the real political motive is to downplay the threat. Nevertheless, the IPCC is the best, most accurate report we have.

And if you don't trust IPCC's impartiality, just whose would you trust? That stupid web site?

theyeti