You can roll your eyes, but it really isn't that important. So what if the MWP was warmer than today? That just means we don't understand internal variability as well as we thought. That doesn't mean that CO2 is suddenly not a problem. In fact, if natural variability is larger than currently thought, then it could be masking some of the current warming. Also, if small changes in forcing can cause big swings (like a very warm MWP) then that means that feedbacks are likely largely positive: resulting in more warming from CO2.

In short, if you want to widen the error bars to include scenarios where AGW will be no problem, then you have to also widen them to include utterly catastrophic scenarios that would call for immediate and drastic mitigation.

Ummm natural variability brings into question how much of the current increase actually is CO2 forcing obviously.

Yes, but natural variability can be either positive or negative.

Exactly?

Anywho, natural variability can't be defeated by burning trillions of dollars in the air either, so it's a big ****ing deal.

The magnitude warming is almost certainly not unprecedented, that does not mean it is unimportant. All climate scientists agree with that. The increase in temperature above what would have happened without anthropogenic CO2 emissions is what matters, as does the future projected warming above what would have happened without emissions. The direct warming due to CO2 emissions is well understood (since about mid 19th century actually - it is about 1.2 oC for a double in CO2 concentration) but the additional warming due to positive feedback, which is likely to be the larger effect, is not well understood.

Do you still not get that you can't just extend the uncertainty in your favor? If the effect of GHG's on climate is more uncertain, then the chances that warming will be far more mild go up, yes, but that also means that chances of much greater warming go up too.

If you keep the CO2 forcings the same. Most people use the uncertainty to question the accuracy of current CO2 forcing estimates.

If you question the accuracy, you are stating that it is less certain. You aren't lowering the estimate.

The variance in the past would obviously diminish carbons current role. The variance isn't purely random.

WAtR -

How is that carbon forcing amount determined, and what kind of error margins apply?

This isn't at all obvious. It's wrong.

A skeptical report to congress turns out to be badly plagiarized.

Edward Wegman, a statistician from George Mason, headed the report. Portions were copied verbatim from Wikipedia.

I dunno if global warming is true or anything, but the "skeptics" don't really come off that well in this thread.

Tactics seem to be similar to that of truthers, creationists etc. None of you have given me a particularly good reason to question the scientific community, but you seem to hope that shouting loudly and frequently about it being a hoax is enough.

lol and there's zero chance you read the thread. Thanks for your comment though.

This business about past variability reducing our estimates of carbon forcing is somewhat misleading.

Many people think (and this may very well be a strawman of any individual here, but it is nonetheless common) is that scientists look at the warming of the last 150 years and say "that warming = CO2 forcing". Hence, if we should expect (by looking at the past) that there is lots of variability then this association would be false because the warming could be due to natural variation not CO2 forcing. Except, this is not at all how the estimates are derivived...they use a bunch of direct measurements and models and the like not the indirect approach of inferring the forcing from the temperature change. Now it may well be that the estimates are wrong - climate science is indeed very tricky - but it could equally be much larger or much smaller from the direct estimates and certainly past variability doesn't minimize a belief in the forcing.

Thanks for changing my opinion of you by... lolling at me and making a sarcastic comment.

You do realize the I'm a neutral but YOU GUYS all suck, let me hyperbolically insult you, shtick is patented right?

Please.

Anyways, Uke, what derivatives of CO2 forcing estimates don't take into account the past 150 years?

Oh they do a whole tonne of direct methods to derive radiative forcing for various gases. One method is to consider for a fixed atmospheric condition and then study the resulting spectral lines and try to deduce a measure of the energy coming off......this is how they derive the first order logarithmic relationship between CO2 and atmospheric concentrations. It has nothing to do with measuring it versus the past 150 years.

I was hoping for some sort of name, where it was used, etc so I could look at it.

Radiative transfer codes like Modtran.

That's all first order effects. Also, there are estimates of CO2's effect from ice ages and the PETM and from the cooling associated with volcanoes. Those are the estimates of feedbacks.

All I did was question your tactics and compare them to those used by creationists and truthers. There are a lot of global warming skeptics who simply loudly shout about it being a hoax, so you can hardly blame me for noticing this.

Surely a rational response would be to correct my ill informed position, and point out the many legitimate issues there are with global warming evidence?

On that note, has anybody got a link to a full critique of the IPCC report? I'm assuming someone has gone to the effort of releasing a free PDF etc. to point out the flaws and how they invalidate the report's conclusion.

So you say this:
And then when you get called on it, you act indignent here:
You remind of an altercation I saw when I was 19 playing tennis. A hot MILF with two boys around 3 and 6 came to the courts. Anyway the 3 yr old walked up to his older brother and suckered punched him. The old brother immediately decks him. The 3-yr old starts crying and points accusingly at his brother. I was laughing my ass off. I didn't see the MILF's expression but she didn't punish the older brother...

If you're going to take pot shots at others then you shouldn't be surprised if they respond in kind...