It is worse than that. A volcano, comet or forest fire can drastically change the weather.

And that doesn't even start to cover issues with cloud cover and atmospheric circulation which already make the models nearly useless - as demonstrated by the nearly continuous string of modeling mispredictions from the Met and NOAA.

The modelers should be required to prove some level of accuracy before policymakers take them seriously. Hansen's claim that he predicted "rising temperatures" is uninteresting. Anyone looking at a temperature graph over the last 300 years would have predicted the same.

Nice try using snow as an example- but that is in question also as it also depends on how much snowfall there is even so- it is a proven fact that snow melts anytime the temperature reaches 32 degrees or higher- and also with clouds- the sun can peak threw

RealClimate already has a post on this paper and and over 70 comments.

http://www.realclimate.org/index.php/archives/2007/10/the-certainty-of-uncertainty/#more-490

Here is a key observation.

Their chief point is that it is probably a bad idea to assign a specific threshold value for CO2 concentrations in the atmosphere, above which "dangerous interference in the climate system" may result. For example, 450 ppm is an oft-cited threshold since this keeps deltaT below 2C using standard climate sensitivities. But the skewed nature of the distribution of possible sensitivities means that it is much more likely that 450 ppm will give us more than 4.5C of global warming rather than less than 2.

I also wonder how we can be so sure that 2C of warming is a bad amount. Supposedly, agriculture productivity starts to fall off above that amount, but there are very few studies that have verified that is the case.

Are there any $$$ spent anywhere on negative feedbacks, or on positive feedbacks towards cooling (those are two very different things)? One wonders...

How hard would it be to build a half mile long tunnel, fill it with air at 300 ppm carbon dioxide, shoot infrared energy into it and measure what gets through? Then do it again with the carbon dioxide at 400, then 500 ppm. Wouldn't this give us an insight into what is really happening?

Here's the abstract:

"Uncertainties in projections of future climate change have not lessened substantially in past decades. Both models and observations yield broad probability distributions for long-term increases in global mean temperature expected from the doubling of atmospheric carbon dioxide, with small but finite probabilities of very large increases. We show that the shape of these probability distributions is an inevitable and general consequence of the nature of the climate system, and we derive a simple analytic form for the shape that fits recent published distributions very well. We show that the breadth of the distribution and, in particular, the probability of large temperature increases are relatively insensitive to decreases in uncertainties associated with the underlying climate processes."

Well, that's a little different. Note the focus on the inability to constrain large increases.

See RealClimate and Nature News for more detailed discussion. The latter closes as follows:

"Politicians are therefore missing the point in attempting to draft policy targets based on a specific level of greenhouse gases in our skies, says Myles Allen, a climatologist at the University of Oxford, UK. 'That's a daft policy,' he says.

"Many climate analysts point to an overall greenhouse-gas concentration equivalent to 450 parts per million of carbon dioxide as the limit at which levels should be stabilized. This is widely predicted to avoid the 2 degrees C warming thought to be the general threshold for dangerous climate effects. But again, that figure is very uncertain.

"Allen says that politicians should focus on the temperature target, and adjust emissions targets accordingly as time passes, rather than committing to a firm emissions target now. 'We need an explicit commitment to do what it takes to avoid 2 degrees C of warming,' Allen argues. 'You don't need to know the climate sensitivity to avoid dangerous climate change,' he adds."

IOW, we are already approaching CO2 levels that will get us into very deep trouble. Climate scientists have known this for about thirty years. The 450 ppm target (which is associated with reductions by 2050 of 80% from 1990 emissions levels) has the virtue of being a good starting point for the needed massive reductions, but as Allen says we had better be prepared to do more as new data comes in. (New data such as confirmation of the recent results that the oceans are indeed losing their ability to absorb CO2 from the atmosphere.)

BTW, that 80% figure is for the whole planet, and assumes that First World countries like the U.S. will do more like 90%. The Lieberman-Warner bill, by contrast, has a goal of 60% by 2050, i.e. way, way short of what's needed. Interestingly the fossil fuel companies and emitting industries are very, very eager to get something passed during the last days of the Bush regime. They fear that regardless of who the new president is she might feel compelled to support a bill with standards more suitable to solving the problem, but that a bill passed now will help delay such an outcome.

mrsund,

That experiment was done a long time ago.
http://www.aip.org/history/climate/co2.htm

another scientist in Sweden, Knut Angstrom, asked an assistant to measure the passage of infrared radiation through a tube filled with carbon dioxide. The assistant ("Herr J. Koch," otherwise unrecorded in history) put in rather less of the gas in total than would be found in a column of air reaching to the top of the atmosphere. The assistant reported that the amount of radiation that got through the tube scarcely changed when he cut the quantity of gas back by a third. Apparently it took only a trace of the gas to "saturate" the absorption - that is, in the bands of the spectrum where CO2 blocked radiation, it did it so thoroughly that more gas could make little difference

mrsund, those lab studies were done many decades ago. You can find a nice narrative in the Discovery of Global Warming, and there should be references to the relevant papers (most of them so old as to not be on-line, though). Atmosphere physics textbooks have all of this in detail, but are not on-line.

That said, this textbook-in-progress (which will remain on-line in draft until it's delivered to the publisher) is a good resource, albeit a temporary one. I think you mainly want Chapter 4.

450 ppm will give us more than 4.5C of global warming

Andrew,

During the Jurassic, CO2 levels were at least 2500ppm and temperatures were at a maximum of 10C warmer. That is a delta of 2100ppm from current levels. The Real Climate "scientists" are talking about a rise of only 70ppm from current levels causing a 4.5C rise. Their numbers make no sense except in the fantasy world of their GIGO computer models.

Supposedly, agriculture productivity starts to fall off above (2C) warming.

I would guess that 2C warming would give a boost to agriculture in Canada, northern Europe and Asia.

Convection changes everything.

PH, Forest Fires do not contribute significantly to climate change. However, as folks in the Western US can attest, drought can lead to a very long fire season.

Maurizio, Yes, lots of $$ have been spent on negative feedbacks. Sulfate Aerosols.

mrsund, A mile long tunnel isn't long enought to simulate the atmosphere. Also, the interaction of water vapor is key.

It is worse than that. A volcano, comet or forest fire can drastically change the weather.

REPLY: Patrick, I sincerely hope you're wrong about that, especially with regard to forest fires. Because if these Cali fires mean we are going to have another 60 degree summer for next year, I will slit my wrists!!! ( I am sure our liberal friends on here would love that!). It's only October and I am already sick of this $%#@-ing cold air!!! If it lasts longer than it's supposed to because of what's going on in SD, then the arsonists who starting this crap should spend the rest of their days rotting in jail, if not worse!!!

Andrew:
your Post: " it is much more likely that 450 ppm will give us more than 4.5C of global warming "

If we take your example and extrapolate it to the values that were common in the past, say 2000 ppm we get some interesting numbers.
Of course I am ignoring all the complex factors that contribute to global temps, but then I think the AGW supporters are as well.

Starting at the oft sited base of 280 ppm.
AGW would suggest that the increase from 280 to 380 produced a 1C rise.
They now suggest that the increase from 380 to 450 will produce a further 4.5C rise.
Ignoring that those two numbers indicate a rapid acceleration in the rise angle, we can say that temperature rises at around 4C per 100 ppm CO2.
If that were true, then the temperature of the planet at 2000 ppm should have been approximately 62 degrees higher than today or more than 75C (167F).
We know that CO2 concentrations have been over 6000 in the past as well.
At that level, temperatures should have been high enough to burn pretty much everything to ash, in the range of 260C (500F).

Simplistic I know, but in my opinion, so is the AGW assertion that CO2 Rise and temperature Rise are closely correlated. It seems obvious to me that CO2 rise is coincident with Temperature rise but not the major cause.

Besides, we all know that realclimate.org will say anything to protect their position. They still defend the Hockey stick for crying out loud. (LOL)

Andrew,

There have been several papers published recently and discussed on this site about how forest fires are warming the arctic, due to soot deposition on snow. As much as 94% of the warming is caused by this.

Also, you ignored the other points about volcanoes, comets, etc. which also have a huge impact on climate.

Patrick Henry forgot to keep reading, or at least keep quoting. From his source:

"Improved physics theory and precise laboratory measurements in the 1940s and after encouraged a new way of looking at the absorption. Scientists were especially struck to find that at low pressure and temperature, each band resolved into a cluster of sharply defined lines, like a picket fence, with gaps between the lines where radiation would get through.(24) The most important CO2 absorption lines did not lie exactly on top of water vapor lines. Instead of two overlapping bands, there were two sets of narrow lines with spaces for radiation to slip through. So even if water vapor in the lower layers of the atmosphere did entirely block any radiation that could have been absorbed by CO2, that would not keep the gas from making a difference in the rarified and frigid upper layers."

So, no, we cannot just fill a hole with CO2. We'd need to simulate the atmosphere. Luckily, we have radiation codes (such as MODTRAN, developed in part by the US Air Force) to give us excellent calculations for CO2's warming effect. The uncertainty comes from feedbacks, as Brett discussed.

"AGW would suggest that the increase from 280 to 380 produced a 1C rise. They now suggest that the increase from 380 to 450 will produce a further 4.5C rise. Ignoring that those two numbers indicate a rapid acceleration in the rise angle, we can say that temperature rises at around 4C per 100 ppm CO2."

You're making a lot of incorrect assumptions. First, Co2 has diminishing efficacy as a greenhouse gas, which is why climate sensitivity is described for a doubling of CO2 (the rise from 100ppm to 200ppm should have the same effect as 200ppm to 400ppm). Second, the warming so far is included in the 4.5C figure. Third, we can still expect to see warming for the CO2 currently in the atmosphere. Finally, comparisons with past climates must also take into account the earth at the time (different albedo, weaker sun, increased volcanism, etc).

Computer models have always been unreliable at predicting climate and weather. Just look at this year's huuricane season for the U.S. Why were the models so far off? The 2007 hurricane season looks like it will be the least active of any season in the last 30 years. Any scientific link between hurricane activity and global warming has been shattered along with the computer models which predicited it. But, if we have an active season next year you can bet it will be caused by global warming, at least that will be the claim of AGW alarmists.

Computers are wonderful tools for a lot of our daily activities but constructing a model of the earth's climate and then plugging in "what if" scenarios just hasn't been feasible. There are simply too many things we do not know or understand about earth's climate to accomplish this.

Computers have been used extensively in weather forecasting with similar shortcomings. Here in Northeast Ohio, forecasters are plagued by unexplained shifts in wind direction and the influence of Lake Erie rendering accurate weather predicitons nearly impossible. And that's just for a small corner of Ohio; imagine trying to predict global climate.

Here is an abstract from from the workTsonis and Wang:

http://www.uwm.edu/~aatsonis/teleconnections.pdf

The gist of the paper is to mathematically treat atmospheric waves as individual nodes on a global climate network. By providing additional "information" (ie data or nodes) from atmospheric teleconnections, they found that the atmospheric models overall performed better. Thus far, they've only teleconnected the NAO and PNAS to mid-latitude northern hemispheric weather patterns. But, the overall affect is to complete the cycle of hemispheric air mass transference from the tropics to the poles.

Like most mathematical networks, the more nodes, the better the performance. Hopefully, thier work can be improve not only long range forecast model performance, but also the GCMs.

"It's only October and I am already sick of this $%#@-ing cold air!!!"

Much of the East Coast is experiencing their warmest October on record. By far.

Gary,

A global temp rise in a range between 2 to 4.5C is only for a doubling of CO2 from pre-industrial levels. Soemthing we can expect in our lifetimes.

Beyond taht, as CO2 levels continue to rise, sea surface temperature eventually start supporting such thick clouds that the earths albedo decreases, thereby limiting global temperature to about 45C. However, by that time people will be seeing tropical hurricanes in polar regions.

In this blog, at 11:28p on 28-Oct, "Patrick Henry" wrote:
During the Jurassic, CO2 levels were at least 2500ppm and temperatures were at a maximum of 10C warmer. That is a delta of 2100ppm from current levels. The Real Climate "scientists" are talking about a rise of only 70ppm from current levels causing a 4.5C rise. Their numbers make no sense except in the fantasy world of their GIGO computer models.

Interestingly enough, an hour earlier -- at 10:49pm -- somebody named "Patrick Henry" posted the same text on the realclimate blog. That, in itself, is no big deal. I suppose that writing a paragraph once and then pasting it into several blogs is a fine way to save time, presuming of course that the author is really the same individual.

I wonder, however, whether Patrick Henry will be as careful to cross-post the responses to his contribution.

In particular, one "Nick Barnes", who observed in responses here and here :
Patrick Henry @81: ~2000ppm is three doublings from the pre-industrial 280 ppm. So, if accurate, a measured 10C at 2000ppm would be confirmation of a ~3C sensitivity.

This is trivial arithmetic.

However, the Jurassic is basically irrelevant to the modern climate because *everything* was different then (for a very abbreviated list: solar intensity, atmospheric composition, locations of continents, oceans, and climatic zones, axial tilt, orbital dynamics, photosynthetic species). So even if we had accurate data on CO2 and temperature from the Jurassic, we could not deduce anything from them about modern CO2 sensitivity.

Patrick Henry @81: and describing the Jurassic as part of "the historical record" must be some new use of the word "historical" of which I was not previously aware.

In other words, even this factoid that Patrick Henry attempted to cherry-pick falls apart upon even brief inspection.

We can only speculate about how many other blogs he submitted this to, and what their reaction was.

Boris,

So even if water vapor in the lower layers of the atmosphere did entirely block any radiation that could have been absorbed by CO2, that would not keep the gas from making a difference in the rarified and frigid upper layers.

I tried unsuccessfully to get you to explain what "making a difference" means in a previous thread, perhaps you can do so here? Can you provide your source?

I'm suspect at the amount of energy that can be transferred through "two narrow lines" to be absorbed by far less CO2 at altitude. It is cold at high altitudes for a reason.

Regards,

Steve

BT,

I thought you would be in a better mood after winning the series.

So the Jurassic is not part of history? Interesting concept. And the laws of physics were different during the Jurassic?

The real climate geniuses want us to believe that there is a very sharp rise in CO2 sensitivity over the next 70ppm, but then it flattens off almost to zero over the next 2000ppm. Do you realize how implausible and quite frankly stupid that is? I do understand that real climate will come up with an answer for everything, no matter how absurd. That is why I don't waste time arguing with them.

Boris,

Angstrom's experiment is well known, and answers mrsund's question. The implications can be discussed endlessly which I'm sure you will do.

I also liked your comment "Co2 has diminishing efficacy as a greenhouse gas". I guess the next 70ppm has been magically excluded from that rule and will be allowed to raise temps by 4.5C in order to raise taxes. BTW- I didn't realize cobalt was common in the atmosphere.

I suppose that writing a paragraph once