Snowball Earth happened before, so by this argument it is credible that it could happen tomorrow. Sorry, but I don’t buy it. The Arctic has been warmer than today probably in the Early Holocene, certainly in the Eemian, at Stage 11, the Pliocene etc. But no huge methane spike has occurred in over 50 million years. Thus if you want to make the case that it is credibly imminent, you have to explain why it didn’t happen then. – gavin

Sure, no problem.

Rate of change.

Non-random forcing.

Accumulation of methane hydrates during recent ice ages.

Approaches to past warm periods have been gradual, and not systematic. There was a certain amount of randomness mixed in. Methane released quickly has nonlinear atmospheric and oceanic chemistry effects which overwhelm oceanic and atmospheric oxidation mechanisms for methane. This makes methane released quickly much, much worse than methane released gradually.

Past forcing has been mostly orbital based, with some amplification from CO2. What we are seeing now is not global warming as usual- it is unnaturally swift and systematic CO2 based forcing, far different from past gradual orbital variation driven forcing.

We’re told, by David among others, that current methane hydrate stocks are lower than can plausibly be the case for past apparent methane catastrophes. Aren’t we coming out of an ice age, with cold ocean water temperatures? Does this make any sense, at all, that current methane hydrate mass would be so low? Have the fundamental bacterial and geochemical cycles that higher lifeforms inhabit changed in some way, that would explain this?

“The sensitivity of Earth’s climate to an external radiative forcing depends critically on the response of water vapor. We use the global cooling and drying of the atmosphere that was observed after the eruption of Mount Pinatubo to test model predictions of the climate feedback from water vapor. Here, we first highlight the success of the model in reproducing the observed drying after the volcanic eruption. Then, by comparing model simulations with and without water vapor feedback, we demonstrate the importance of the atmospheric drying in amplifying the temperature change and show that, without the strong positive feedback from water vapor, the model is unable to reproduce the observed cooling. These results provide quantitative evidence of the reliability of water vapor feedback in current climate models, which is crucial to their use for global warming projections.”

Who told you the lie that positive water vapor feedback is uncertain? Are they the same people who tell you that warming is no threat, we don’t have to act now, and our economic models show any action to limit CO2 emissions will destroy the economy? Do you trust their economic models more than climate models?

Recaptcha – blistered become

Please someone explain why it “makes sense” to average the results of multiple models none of whose accuracy has been demonstrated based on observations of actual conditions.

Why should public policy be implemented based upon faith—when data shows there is little reason to accept the faith in GCM’s?

Ray, you started well and went all grumpy SOB at the end! – likening my thought processes to those of a teenager.

Please try and understand that not everyone has the knowledge that you, and other contributers, have and try and understand how, and where, reasonably intelligent lay people get their “knowledge”.

Throughout the whole of my education I was taught that the planet has experienced various major clamatic events. I believe, because that was what I was taught, that dinosaurs probably became extinct because of an asteroid stike which sent plumes of matter into the skies – which darkened (cooled) the planet and wiped out much natural life.

I believe, this event, or others, lead to an ice age such that my country (England) was once frozen over for many years.

I was then lead to believe that as the dust settled (literally) the planet started to warm (naturally) and the ice started to retreat (and still does).

You went on to say:
…………………….
If the temperature is rising, then either energy in must be increasing or energy out must be decreasing.
………………………..

At the risk of incurring your ire, is this really correct?

It is surely not suggested that the sun was getting “hotter” after the ice age – only that more of the sun’s energy was getting through because the dust settled.

It seems logical to me (although this may be a big mistake) that the earth would actually have an equilibrium point that the average temperature would hold at, or return to, – if volcanoes and asteroid stikes didn’t occur and man was not affecting the atmosphere (and that changes in the sun was not affecting temps)- and subject to anolomolies caused by weather sytems around the world in any year.

If there is no “equilibrium point” then the alternative is that momentum takes things to a tipping point one way or t’other over time and man’s efforts to affect this would probably be in vain.

As I hit the “say it” button …. I am diving under the table.

Let’s do a little thought experiment:

One of us parks his car on a hill. But, due to negligence, he forgets to set the parking brake, and he leaves the wheel turned the wrong way. So the car rolls downhill, killing an old woman, a postman, and a small dog.

What is his ethical position?

Pretty terrible, right?

Now, suppose one of us suffers from hubris, and believes his ability to predict the unpredictable is so great that he can publish a worst case scenario. This person ignores a lot of established science to do this. This falsely reassures a lot of people, including impressionable students and congresspersons who take a lot of oil industry money, anyway, and so don’t need much convincing. A necessary war on climate change is called off, oil corporations profit for a few more years- and then methane releases get out of hand, and thousands of years of climate grief result. This kills billions of people, as in Lovelock’s scenarios, and what progeney are left curse our names forever.

What is the ethical position of this person?

Is it better or worse than the guy who parked his car badly?

Eminent climate scientist Michael Mann has written a book describing what’s it’s like to be on the receiving end of an orchestrated anti-science campaign. The Amazon.com comments page has collected a swarm of negative reviews from climate science denialists.

“… Antarctic sea ice is increasing. This is expected from climate modeling.”

http://moregrumbinescience.blogspot.com/2010/03/wuwt-trumpets-result-supporting-climate.html

[Response: Be a little careful here. 'climate modelling' is not a monolith, and especially for a situation where a) there is a lot of noise and not a lot of signal, b) there are a lot of issues (climatological biases, multiple forcings), I doubt very much that all climate models suggest the same thing. I'm sure that someone has written a paper on the CMIP3 Antarctic sea ice changes, but I don't have it at hand. This would be the appropriate source for any statements. - gavin]

Above, “Dan” replies to “Dan H.” who posted a big bundle of denial at 156.

173 Dan says: 8 Feb 2012 at 6:42 PM
> … We are talking about
> the warming that has occurred
> since the 1970s which can not be
> explained by natural causes alone.

and Dan H. says: 9 Feb 2012 at 9:15 AM
> Dan,
> Where are you getting the idea that
> warming since the 1970s can be
> explained by natural causes alone …