Re the title of this thread - If you had actually delved into the explanation itself rather than the initial summary, then it would make sense. If you take the trouble to read past the very first introductory post on that thread, you'll find your answers. If you don't find it there then ask.

Your question of "What percentage" is a loaded question.  For a start, it concentrates on the relatively minor temperature rise up to the present day rather than that projected by an increased concentration of greenhouse gases - because that is the real issue. 

That thread goes on to talk about natural variability. That's a key feature.

Do you think that human beings could have survived during all previous paleoclimates? If not, then your point about the age of the Earth is academic.

If you're prepared to read up some of the actual explanation itself rather than making a superficial attack on the title page, then I'd be happy to continue in a non-adversarial manner.

Maqqa wrote on Dec 22^nd, 2011 at 7:37am:

IT'S ALL ABOUT SMALL ADVANTAGES, I MEAN DISADVANTAGES.

I WAS JUST TRYING TO TALK IN TERMS MR NIGHTMARE WOULD UNDERSTAND! 

What everybody is saying is that human greenhouse gas emissions are not presented in the context of all other factors making up the climate. This is what you call a loaded question. But it isn't. It is a simple enquiry after the entire cast of characters that mak up climate and any change of it.

Maqqa wrote on Dec 22^nd, 2011 at 7:37am:


If you take all the greenhouse gas that has been produced since industrialisation, a large proportion of that has ended up dissolved in the ocean.

The warming caused by the continuing increase in CO2 will give rise to more of that CO2  being emitted by the oceans, giving rise to additional warming. So you can see that even past emissions are not yet fully accounted for in terms of temperature rise. For that reasons, you can't provide an answer to the question "How much of the warming is due to human activities?", because the full outcome depends on future activities, and it depends on when you draw the line. 

However, if you subtract the human influence, the global temperature  rise since industrialisation would be slightly negative (it would have dropped slightly). So it's possible to answer your question by saying "the human contribution is greater than 100%"

CO2 and water vapour are greenhouse gases. Whenever you heat a body of water, more of that water on average ends up in the atmosphere, and that amplifies the effect of the CO2 alone.

You're probably not really interested in explanations, but let's take an analogy unrelated to climate. A small town (Maggasville) is  situated by the central  portion of a river as it flows into the sea. The river has to flow between two hills before it heads out to sea.  Maybe once in a thousand years, the area occupied by the town is prone to flooding.

Now a second river runs from the same source and flows through some wetlands out to sea.  A mining company (Soren Mining) discovers gold in the  wetlands and decides to divert the second river so that it runs into the first river.

Now one year, there is more rain than average and Maqqasville is flooded. Usually, that amount of rainfall would not lead to flooding, but the additional water from the second river resulted in additional flooding.

Soren Mining makes the point that there have been floods in the past, and that the flooding was caused by rain falling from the sky.  Anybody who states that Gold mining causes flooding is crazy. Gold is beneficial. So is water. If you didn't have any water, you'd die of thirst. So more water must be a good thing - right?

So flooding is natural. Anybody can see that. They also ask the question, if the flooding was caused by their activities, then what percentage of the total floods were caused by their activities rather than natural events. They agreed to pay compensation based on this figure. So the river itself has been there for 5 million years and there have been around 5000 floods since then, so the percentage of their contribution must be less than  0.02 percent.

It's a simple question. What proportion of the floods were man-made as opposed to natural? None of you Maqqasville scientists can answer that question, so until such time as you can provide a number,  we at Soren Mining will continue to mine the wetlands as we've done in the past, and will pay no compensation. (Good grief - these Maqqasville people want to tax water. How stupid is that?  Water is natural)

Now the topic we're discussing is similar to that analogy, except that there have been no "floods" yet.

muso wrote on Dec 25^th, 2011 at 7:42am:

 

muso wrote on Dec 25^th, 2011 at 7:42am:



Probably because that river hasn't been divertd, either.

A lot of the doom-mongering is based on just that kind of sleight-of-hand insertion of assumptions and wild surmising, such as an entire river being causally diverted into another river held up as a devnt analogy for a tiny increase in atmospheric CO2 proportions (a doubling bringing it to 0.05% or even 0.06%, where a 0.0286% increase is doing the work of the river of doom) .

Re flood-risk: if it was 1000 yeears betwen floods with one river and no wealth genration by Soren & Co, and say, 500 years with two rivers and wealth generation, the question is: which one would you rather: a once in 500 years flood damage to Maqasville or 500 years worth of wealth generated by Soren Mining?  The Netherlands is a country that has been  under the sea levl for centuries and is one of the wealthiest places on earth. Netherlands or Nepal? Doom mongers should all head to Nepal.

Soren wrote on Dec 27^th, 2011 at 2:31pm:

Yeh, I think quite a few people will be keeping their eyes on the Netherlands somehow!!