The IPCC May Have Outlived its Usefulness

[RenewableCandy]

How do we know that last supposition of yours is indeed the case? Supposing at some temperature a large, but *finite*, amount of (say) Methane is unleashed. Then it would start with a larger temperature increase, which would tail off with time.

How can anyone know whether or not we'll overtop the largest feedback that happened in the Eocene? Perhaps something important is different now?

[fifthcolumn]

How do we know that last supposition of yours is indeed the case? Supposing at some temperature a large, but *finite*, amount of (say) Methane is unleashed. Then it would start with a larger temperature increase, which would tail off with time.

How can anyone know whether or not we'll overtop the largest feedback that happened in the Eocene? Perhaps something important is different now?

Such an event has in fact taken place during the Eocene, so if it was necessary to burn up all the clathrates to get the massive warming in the Eocene (by the way I was mistaken: it was only 6C not 8C so mark down my corresponding estimates for feedback effects to more like 2-3C) then there's NO WAY we're going to turn the Earth into venus even if we burn every last ounce of coal and release the clathrates deliberately.

Also for light reading, here you go an unbiased source:
http://en.wikipedia.org/wiki/Paleocene% ... al_Maximum

[RenewableCandy]

That's very interesting but it also mentions that there are probably a lot more clathrates down there now (waiting to be released) than there were before the PETM started.

The present-day global methane hydrate reserve is poorly constrained, but mostly considered between 2,000 ~ 10,000 Gt. However, because the global ocean bottom temperatures were ~6 degree C higher than today which induces much smaller volume of sediment hosting gas hydrate than today, global hydrate amount before PETM was thought much less than present-day estimates.

But really, without a time-machine and a thermal space-suit, we'll never know what's going to happen I'm not a Venus person myself but I wouldn't rule it out.

[fifthcolumn]

That's very interesting but it also mentions that there are probably a lot more clathrates down there now (waiting to be released) than there were before the PETM started.

The present-day global methane hydrate reserve is poorly constrained, but mostly considered between 2,000 ~ 10,000 Gt. However, because the global ocean bottom temperatures were ~6 degree C higher than today which induces much smaller volume of sediment hosting gas hydrate than today, global hydrate amount before PETM was thought much less than present-day estimates.

But really, without a time-machine and a thermal space-suit, we'll never know what's going to happen I'm not a Venus person myself but I wouldn't rule it out.

But just to poke some gentle fun Candy: you had already made your mind up and it took me (an evil denier) to point you in the direction of some very relevant material you didn't know about.

How is it you can have made your mind up already? Do the climate guys throw better parties than the boring middle of the road business types?

[RenewableCandy]

People didn't actually know this but I'm still undecided on the full-on Venus scenario. I'm also undecided on whether Chateau Renewable's going to get burned to the ground this year but we still have insurance.

I've been around long enough, and in the same location, to see changes in weather that I personally find unsettling.

And the clincher, really, is what the CO_2 is doing to the sea. This is why all the geoengineering stuff about the temperature is so irrelevant.

[biffvernon]

James Hansen (who, you will remember, was the main guy in working out how Venus's climate became, before turning his attention the our planet) says that IF we burn all the coal, oil, gas, tar sands and oil shales, then the Venus syndrome is 'a dead certainty'. Of course our civilization will cease to be long before we've managed to burn that much carbon so it probably won't happen.

[biffvernon]

And the clincher, really, is what the CO_2 is doing to the sea. This is why all the geoengineering stuff about the temperature is so irrelevant.

Very true and much ignored.

[fifthcolumn]

James Hansen (who, you will remember, was the main guy in working out how Venus's climate became, before turning his attention the our planet) says that IF we burn all the coal, oil, gas, tar sands and oil shales, then the Venus syndrome is 'a dead certainty'. Of course our civilization will cease to be long before we've managed to burn that much carbon so it probably won't happen.

biff: I'm not going to mince my words here. Your above quote is just bullshit.

Venus has 96.5 percent carbon dioxide in its atmosphere and the pressure is greater (i.e. much MORE atmosphere).

Remember greenhouse warming is not LINEAR, you have to DOUBLE carbon dioxide to get each x degrees of increase. We'd need somewhere around 15 doublings to get to the Venus composition and I'm afraid there's nowhere near a million times the current oil/gas/coal currently being burned available anywhere on Earth.

Unless you propose a very long pipeline to one of Jupiter's moons to siphon off the methane I think it's safe to say we'll be OK.

[UndercoverElephant]

A full-on Venus-style scenario is almost impossible, IMO. I think it is almost inevitable that we'll force enough warming to set off the various positive feedback mechanism that are capable of raising the average temperature by 8 to 10 degrees. But that sort of warming will be lethal to most of the human race - it will either wipe us out completely or reduce our numbers to the point where we can't do any more serious damage. Without humans to aggravate the situation even more, the Earth will recover.

Even a ten degree rise won't take us to the maximum of 55 million years ago, and the planet recovered from that.

[clv101]

Before calling 'bullshit' maybe you should figure out what Hansen actual means by "Venus syndrome".

[SleeperService]

The Theories about Venus's atmosphere modelling CAN be applied to Earth. In fact every day it's atmosphere loses tons of material that's blown off in a tail that reaches Mars orbit.

The effect on Earth will differ as a) it has a much stronger magnetic field and b) it's further from the sun.

What Hansen suggests it's perfectly possible, whether it's 100% accurate given limitations of computer modelling well mind we'll know in due course as we seem hellbent on running a global experiment.

[snow hope]

Before calling 'bullshit' maybe you should figure out what Hansen actual means by "Venus syndrome".

Why don't you tell us then?

[fifthcolumn]

Before calling 'bullshit' maybe you should figure out what Hansen actual means by "Venus syndrome".

Why don't you tell us then?

I second that. I already went ahead and explained why it was bullshit. Now refute my claim by explaining in great detail why the Earth will turn into Venus. And if it's not going to turn into Venus then WHY THE HELL is it called that?

Rolls eyes.

[clv101]

My understanding isn't that "Venus syndrome" means the Earth gets the same atmosphere as Venus today. It refers to a runaway greenhouse effect where the positive feedbacks stop being checked by negative feedbacks as they have in the past. It describes a process not a state.

[Ludwig]

My understanding isn't that "Venus syndrome" means the Earth gets the same atmosphere as Venus today. It refers to a runaway greenhouse effect where the positive feedbacks stop being checked by negative feedbacks as they have in the past. It describes a process not a state.

I agree with Snow and Fifth, then, that the name is misleading, and seems contrived to shock. It shocked me when I first read about it. I didn't even register that Venus's atmosphere is 96.5% CO2 - I was so "certain" that the scare stories were true that I switched off my critical faculties. A lesson there for me.