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snow hope · Posted: Sun Sep 04, 2011 8:39 pm Post subject:

Okay, there is some difference, lets tease this out a bit further then. Smile

Who would care to say how much man is responsible for global warming, according to the IPCC? I bet Chris knows? Wink

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And that was the fatal mistake. Me

Keela · Joined: 05 Sep 2006 Posts: 1933

It's a tricky question.

If climate is close to a tipping point (with all the things that brought it there being natural) and another manmade factor is added that brings the climate to the cruical tipping point, then how much is that last factor responsible?

Or to use an old saying as an example - If you are loading a camel with straw, is it the first straw or the last one that breaks it's back?

Or another thought exercise - I take migraines and I know there are a load of things that contribute to them. Migraines also work on a tipping point or threshold thing. I know there are days that I am more at risk of reaching that threshold and so I am particularly careful to avoid things such as cheese that usually have little to no effect.

So imagine if, on a specified day, I would get migraine with cheese and without I wouldn't: would the cheese be 100% responsible for the migraine? Or simply one factor amongst many? Tough call.

For me the decision is easy - Avoid cheese when other factors beyond my control are also causing me to approach a migraine!

So I haven't quite answered your question, but instead I'll ask you to think about how you would measure your "how much" - especially in relation to the tipping point concept.

biffvernon · Joined: 24 Nov 2005 Posts: 13914 Location: Lincolnshire

Perhaps a better analogy: walking along a busy road but staying on the pavement is fine - take a step sideways, splat.
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An Inspector Calls · Banned Joined: 27 Jan 2011 Posts: 965

90 % likely . . . 90 % of . . . yes, there's a difference but, broadly, the impression is similar.

Why worry about the possibility of a tipping point? We now know, thanks to the re-establishment of the MWP (following its temporary cancellation by Mann et al) that it was warmer than present day during that period, and that subsequently the temperature dipped into the LIA. It was even warmer during the early holocene. So there can be no tipping point at temperatures similar to those at present when they are below the temperatures of the MWP. If there were such a tipping point, temperature would have 'run away' during the MWP.

Now we 'know' from the IPCC that the warming of the earth in the last 100 years, 0.75 degrees, is almost certainly due to CO2 emissions. And since the dependency of temperature on CO2 concentration is logarithmic, we can easily calculate, from the most basic physics, what the projected temperature rise might be for future emissions.

Over the last 100 years, the atmospheric concentration of CO2 has risen from 280 ppmv to 390 ppmv. What would happen if we caused the concentration to rise to 560 ppmv? We are not confident about the various constants we must use in the equation relating CO2 concentration to temperature rise, but by using logarithmic ratios we can cancel all these unknowns out. In other words, we can use the 'experiment' of the last 100 years as a proven model for the future.

So, the warming will be given by this simple ratio:
Warming for CO2 at 560 ppmv = (The warming caused between 290 and 280) * [log(560/280)/log(390/280)]

that is

Warming for CO2 at 560 =0.75*log(2)/log(390/280)
which is 1.6 degrees.
As we've already had 0.75 degrees to date, the warming for a rise from 390 to 580 ppmv is 0.8 C.

If that rise doesn't take us to temperatures above those seen in the MWP (or the early holocene), there'll be no 'reaching the tipping point'.
http://en.wikipedia.org/wiki/Holocene

kenneal - lagger · Posted: Mon Sep 05, 2011 3:43 pm Post subject:

The sun has been causing warming and cooling on its own for the entire history of the solar system. Yes, the sun caused the MWP and the LIA and it's about to cause another LIA in the next few years. The odds are that once we come out of the new LIA we will have another extremely warm period. If you add on top of that the warming caused by an increasing amount of CO2 in the atmosphere we will get some very uncomfortable temperatures to put up with.

If the sun goes into hibernation as it did in the LIA, and as it's thought to be about to do, we should get temperatures on a par with the Maunder Minimum. If we don't get those temperatures it will give us some idea of the amount of warming being caused by the CO2.

I am taking precautionary measures which will enable me to keep warm and grow my own food during the upcoming economic recession and/or collapse. These will also mitigate against PO and GW so I'll be a winner three times over.
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It is very, very, very serious indeed. This is the big one!" Professor Tim Lang, APPGOPO, 25/03/08. And he was talking about food, not oil or the economy!

An Inspector Calls · Banned Joined: 27 Jan 2011 Posts: 965

If we go into another LIA you won't see any warming for centuries. And my house has half the heat load of yours.

biffvernon · Joined: 24 Nov 2005 Posts: 13914 Location: Lincolnshire

kenneal - lagger · Posted: Tue Sep 06, 2011 1:33 am Post subject:

An Inspector Calls · Banned Joined: 27 Jan 2011 Posts: 965

kenneal - lagger · Posted: Tue Sep 06, 2011 4:27 pm Post subject:

An Inspector Calls · Banned Joined: 27 Jan 2011 Posts: 965

I've always found mains electricity to be very sustainable, hardly ever disappears. And I've got better things to do with my time than chopping wood all day.

Anyway, mustn't keep you from your little chopper.

kenneal - lagger · Posted: Tue Sep 06, 2011 6:05 pm Post subject:

kenneal - lagger · Posted: Tue Sep 06, 2011 6:18 pm Post subject:

Mains electricity can never be said to be sustainable when it wastes about 60% of the fuel use to generate it. It can never be sustainable as long as it uses fossil fuels as a generation source because fossil fuels won't last forever.

It is also debatable how sustainable fossil fuel derived electricity is on an individual basis as the cost is set to rise dramatically over the next few years as the BRICS countries continue their 10% growth. Even the government has been warning people over future fuel cost rises. The maths of this 10% growth is that those countries, which comprise at least a third of the world's population, will have to double their consumption of everything they have used in the past in the next seven years.

Can you imagine the effect that will have on all commodity prices? I'll happily go back to chopping my wood and growing my own food thank you. And thanks to my insulation program, I will be chopping ever less amounts of wood, even if the weather does get substantially colder.
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It is very, very, very serious indeed. This is the big one!" Professor Tim Lang, APPGOPO, 25/03/08. And he was talking about food, not oil or the economy!