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http://newsbusters.org/blogs/noel-sheppard/2008/04/17/worlds-oldest-tree-rewrites-climate-history-challenges-global-warming http://www.climate-skeptic.com/temperature_history/ http://www.longrangeweather.com/global_temperatures.htm Everybody can make the data do tricks for them. First it was Global cooling, then it was Global warming, then it was Climate change Because you know that change is good right ?

This is a common error, frequently made be people who don't understand mathematics and graphs. As long as there is random noise in data, there will always be "plateaus" where things look stable but the underlining trend continues. In the case of global warming, if you try you can actually find a series of continuous downward slopes so that any year of the temperature record can appear to be part of a declining trend, while actual temperatures rise consistently.

You mean like focusing on the statistical noise in the last 100 years instead of the big picture?

http://www.longrangeweather.com/global_temperatures.htm

I agree that such focus on the short-term trends can be very misleading.

1) How accurate can we judge the entire planet's average temperature in the year 1800? The graph shows swings from year to year in the 0.2 C range. Can we really judge the average surface temperature of the planet with 0.2 degrees Celsius?

Take a look at the grey band - it's more obvious in the second graph, the 10 year moving average. The grey band is the 95% uncertainty interval for Berkeley's calculation of the average temperature - statistically on each data point there is a 5% chance that the real average temperature lies outside the grey band. You will see that in the year 1800, the grey band is massive: +/- 0.5 degrees. But over time, as there are more measurements around the world, and those measurements have less randomness in them (i.e. get more accurate), the uncertainty shrinks pretty slowly.

2) Also, the chart shows 200 years. This is a blip on the scale of climate science. If you look at the climate history on a much, much larger scale, you'll find that 200 years means nothing. For example, the chart on this page shows that we are much cooler than the average. An sharp increase in average temps would help put us "right".

This is true - no matter how much we heat up the earth, life will survive. But if the climate changes too much from our current conditions, then there will be massive changes. Lots of creatures will become extinct (eventually new ones will evolve, taking advantage of the abundance of food/lack of predators but that happens very slowly) and we will probably have to totally rethink our farming practices. We should move our cities too given that many would no longer be well-situated, but what would probably happen is that we turn up our air-conditioners and burn even more coal. I concede that the effects of climate change are less well understood (at least by me!) than that it is happening.

Or this chart which goes back 4500 years, shows that we just came out of an ice age, so a temperature increase would be expected, and also negates your Berkely graph.

Seriously? I give you the Berkeley graphs, which appear to have used a pretty rigourous method, where you can download their temperature data and source code, and is being peer-reviewed, and you rebut this with a graph that does not have a labelled y-axis and appears to have been drawn with a bezier tool? If you want to convince me that there is no scientific consensus, i.e. that researchers who know what they're doing and are doing it properly, disagree that global warming is happening/is a problem, then please stop using graphs like that. Especially when they disagree with the graph I provided, which gives its sources (IIRC, every temperature measurement they could get their hands on), and includes three other groups' sets of numbers on the same axes - none of which agree with the graph you provided.

Or, finally, this page which shows a whole slew of charts, most of which show that we are in a cold period of climate history, and an increase in average temperature would get the earth back to the "normal" range.

Again, the really-long-range graphs don't have much to do with the current debate, because I'd like life to survive in its current form as much as possible. When large-scale, seemingly-irreversible (on the scale of centuries) changes are made to the only planet we live on, I get nervous about the potential for things to go wrong.

There are too many graphs on that page to go through them individually, but it doesn't give that site any credibility to include graphs like this one, which show very suspicious behaviour - local temperature swings around wildly and then the music st

Speaking of graphs, I find this one really scary, and would want to see it flatten out or drop for a good few years before I stop caring about my energy usage.

Just taking a quick gander at that particular graph, I notice that it covers 200 years of surface temperature. This brings a couple of points to my mind:

1) How accurate can we judge the entire planet's average temperature in the year 1800? The graph shows swings from year to year in the 0.2 C range. Can we really judge the average surface temperature of the planet with 0.2 degrees Celsius?

2) Also, the chart shows 200 years. This is a blip on the scale of climate science. If you look at the climate history on a much, much larger scale, you'll find that 200 years means nothing. For example, the chart on this page shows that we are much cooler than the average. An sharp increase in average temps would help put us "right". Or this chart which goes back 4500 years, shows that we just came out of an ice age, so a temperature increase would be expected, and also negates your Berkely graph. Or, finally, this page which shows a whole slew of charts, most of which show that we are in a cold period of climate history, and an increase in average temperature would get the earth back to the "normal" range.

Both match well with your critical reasoning skills, though. It is, however, a quite apt example of relentless propaganda creating a core of "unshakable believers" on the denialist side,

My critical reasoning skills are far better than those of name-calling zealots pointing a finger and chorus to Sir Bedevere: "She's a witch! Burn her! Burn! Burn her!" at those who identify the reality of the basis of their poorly substantiated claims:

[We have NO] agreement on a model for generating a single figure of merit for "earth temperature" it is absurd to discuss changes in fractions of a degree. There are too many parameters in the definition, and it's easy to get any result you want by playing with the definition of "temperature." There are no continuous measures from 1880 to 2000; all have to have "adjustments" and the adjustments are often larger than the error margins.
[other post}
You can prove anything if you can make up your data, and just about anything if you can select your data. But it isn't science. - Jerry Pournelle

Also, how can we trust computer models when the models can't and don't account for Medieval Warm and the Little Ice Age, we have little data from the Southern Hemisphere prior to the Voyages of Discovery. If the hypothesis cant even be corroborated with the historical data we DO have with the tools used, how dependable are they for prediction? AGW is is the antithesis of "the progress of science", it is a hypothesis at best, and we lack sufficient data to even falsify it, let alone promote it as a forgone conclusion. How about something with a more climatic timespan: http://www.longrangeweather.com/global_temperatures.htm If the data are correct, it looks like:
A) consecutive cold periods and warm periods appear to be getting closer together.
B) cold cycles look to be trending cooler.
C) warm cycles also appear to trend slightly cooler and terminating more abruptly.
See also previous discussion on the absurdity of their claims: http://slashdot.org/comments.pl?sid=1629458&cid=31961726
Please educate us lowly "deniers", oh blond cheerleader, what do your priests say is the "proper" "global temperature" for which we should be striving with their demanded herculean efforts and trillions in expenditures to be put forth on this hand-waving of smoke in front of their carefully placed mirrors.?

[We have NO] agreement on a model for generating a single figure of merit for "earth temperature" it is absurd to discuss changes in fractions of a degree. There are too many parameters in the definition, and it's easy to get any result you want by playing with the definition of "temperature." There are no continuous measures from 1880 to 2000; all have to have "adjustments" and the adjustments are often larger than the error margins.
[other post}
You can prove anything if you can make up your data, and just about anything if you can select your data. But it isn't science. - Jerry Pournelle

Also, how can we trust computer models when the models can't and don't account for Medieval Warm and the Little Ice Age, we have little data from the Southern Hemisphere prior to the Voyages of Discovery. If the hypothesis cant even be corroborated with the historical data we DO have with the tools used, how dependable are they for prediction?
AGW is not a theory, it is a hypothesis at best, and we lack sufficient data to even falsify it, let alone promote it as a forgone conclusion.
How about something with a more climatic timespan:
http://www.longrangeweather.com/global_temperatures.htm If the data are correct, it looks like:
A) consecutive cold periods and warm periods appear to be getting closer together.
B) cold cycles look to be trending cooler.
C) warm cycles also appear to trend slightly cooler and terminating more abruptly.
See also previous discussion on the absurdity of their claims: http://slashdot.org/comments.pl?sid=1629458&cid=31961726

I went off looking for charts of global temperature and I found this but along the way I discovered a meteorologist called Randy Mann.

So if you trust NASA there has been a steady increase in global temperature from 1900 accelerating in 1920 and about 1965. Must be my fault. I was born in 1965.

More global citations may include here

They draw a graph (from the gut it seems), with volcanic events all over, often when the graph crosses the Zero line in either direction, and they conclude that volcanoes (together with "decresed solar radiation" for which they have no data) are responsible for long-time cooling?

A citation at least. One that can be debated as to its correctness or applicability. Being a single location, especially at one end of the planet, it's hard to correlate it to the rest of the planet.

More global citations may include here or here, both of which throw some concern on taking your citation as the ultimate word.

Basically, for a theory to hold as correct and significant, it must surpass the noise in its environment. Here, anthropogenic sources of global climate change need to surpass the noise in history that predates those sources. They don't. This means that if they exist, they are not significant. That doesn't mean, however, that they are not significant for the arctic.

Oh, and as far as its correctness, I do have to wonder about this quote from page 2 (yes, I'm reading the citations):

"The big issue is, when you melt ice, the sea level rises -- that's a global issue, and that has major impacts."

Um, this is the arctic. When you melt that ice, the sea level will remain unchanged. Perhaps if they don't know the basics of volume-mass correlations of floating bodies, which I re-learned in my first year of university, the rest of their science might be a bit suspect, too. Just saying. Now, if they were talking about the Antarctic, well, that's another story, since much of that ice isn't floating, it's held on top of actual landmass. Ok, so if they're referring to ice being lost from Alaska, Yukon, Northwest Territories, Nunavut, Greenland, etc., there'd be some rise. But, again, we need to talk about significance. Crying wolf over small things is not endearing. And won't help the movement over the long term as people get upset about being called to rallies over those small things, and will assume that should a big thing occur (like melting of the antarctic) it'll just be another cry of wolf and be ignored.

And the rate at which change is happening is unprecedented.

I'm not really arguing with you, but 'unprecedented' is relative what slice of time you look at and who's graph you pay attention to.

If you look at temperature records provided by proxy sources (ice cores, tree rings etc...) over hundreds of thousands of years - on many of the graphs you'll find - it's pretty clear that the last millennium has been nothing unusual.

If you look short term though, (past few hundred years) it looks pretty damning.

• Ice Ages: temperature over 450,000 years
• Global Temperature Trends From 2500 B.C. To 2008 A.D.

Funnily enough, this choice is similar to what happened in banking in the past 10-20 years. Banks had risk management departments, and the requirements were strengthened by government legislation. But the bosses discovered they could wriggle out of the straitjacket imposed by their risk management computer systems just by lengthening the baseline period used. Thus, if you looked at the past 1-5 years, it would be obvious that risk was excessive; but extend that period to 15 years, and average out the risk over that longer time - and hey presto, acceptable risk! (Until the floor falls out from under you, that is).

And the rate at which change is happening is unprecedented.

I'm not really arguing with you, but 'unprecedented' is relative what slice of time you look at and who's graph you pay attention to.

If you look at temperature records provided by proxy sources (ice cores, tree rings etc...) over hundreds of thousands of years - on many of the graphs you'll find - it's pretty clear that the last millennium has been nothing unusual.

If you look short term though, (past few hundred years) it looks pretty damning.

• Ice Ages: temperature over 450,000 years
• Global Temperature Trends From 2500 B.C. To 2008 A.D.

KURTZ: Barbara Starr, CNN did mostly quick reads by anchors of these numbers. There was a taped report on Lou Dobbs Tonight. Do you think this story deserved more attention? We don't know whether it is a trend or not but those are intriguing numbers.
BARBARA STARR, CNN PENTAGON CORRESPONDENT: But that's the problem, we don't know whether it is a trend about specifically the decline in the number of U.S. troops being killed in Iraq. This is not enduring progress. This is a very positive step on that potential road to progress.
KURTZ: But let's say that the figures had shown that casualties were going up for U.S. soldiers and going up for Iraqi civilians. I think that would have made some front pages.
STARR: Oh, I think inevitably it would have. I mean, that's certainly -- that, by any definition, is news. Look, nobody more than a Pentagon correspondent would like to stop reporting the number of deaths, interviewing grieving families, talking to soldiers who have lost their arms and their legs in the war. But, is this really enduring progress? We've had five years of the Pentagon telling us there is progress, there is progress. Forgive me for being skeptical, I need to see a little bit more than one month before I get too excited about all of this.

HERE is the video. Watch it and tell me that the media is slanted to the right!
And don't even get me started on the AP. Google Pallywood and watch the video of that.
I've seen the AP ac