When you are trying to mix science and politics, when you are trying to use cherry picked science to push your political agenda, you have to be careful about your claimed threat. If you choose too little, say one degree, everyone will scoff and say what could one degree hurt. If you go too high you will loose your credibility. If they add water vapor and exaggerate its affect they can argue that our CO2 may increase the climate by 2C. Because that is the highest they can reasonably suggest, that is the number they have decided to use as the tipping point, the doomsday amount, the amount we must never go above. We must immediately surrender all rights and enact their "solutions" which just happen to be their political agenda.

What your notrickszone article fails to mention is that the 2oC figure is a very conservative estimate agreed upon by government representatives. It is based on scientific findings but had the scientists actually had a say in the matter, the figure would have been lower.

<>

Because the warming occurred gradually over 4,000 years and because the human population was much smaller, ie, there weren't vast amounts of environmental resourced needed (all prone to weather and climatic shifts) to feed 7 billion people like we have today.

It is not a scientific fact, but a policy choice to which science was produced to justify. The problem they have is that a certain amount of warming is going to happen, as policies cannot flip overnight. However, if they pick too high a number like 3C they are contradicting themselves completely and leaving open the possibility of achieving the goal with no policy action, and this amount is the middle of their likely range, at least in the previous report. If they pick too low a number, the chance of achieving it disappears entirely, and they might as well go home, as they cannot scientifically defend that the target is achievable.

So they pick a number that is low, but still theoretically achieveable like 2C.

This allows them to still recommend policies without being forced to admit it is simply impossible given the emissions levels.

However, since they first adopted these targets, emissions have gone up, and the chances of achieving that are also impossible. It wouldn't surprise me if they changed the science to make achieving this goal more likely. For example, if they adopted the Beenstock & Reingewertz claim that an increase of CO2 is what drives global warming, not the level itself.

2c is not meant to be an exact number it is considered a point above which we will start to see changes in ice and sea level which will be quite bad for our society.

Your point ignores some quite solid data (as usual) the period you are referring to also had a very strong rise in sea level, now I wonder why you failed to mention that.

The period in question - http://en.wikipedia.org/wiki/Holocene_cl...

and the associated sea level rise. - http://en.wikipedia.org/wiki/File:Post-G...

From around 4000 years ago sea level rise tailed off and pretty much stopped ~2000 years ago.

During the HCO sea level rose ~60m you also seem to have neglected to mention that.

It takes ice/sea level quite a while to react to temperature rise but the current rate (which deniers try to call small) is in fact a return to the sort of rate of rise we saw 7000 years ago and well above anything seen in the last 4000 years.

As for our ancestors, look at the science and not the denier blog hype and scientists are mostly concerned about the effects of sea level rise on our infrastructure and longer term of the effects on crops from our now massive farming infrastructure. Our ancestors had neither most where still hunter gathers, some lived in small villages but sea level rise would have taken generations. A mud or thatched hut is a little easier to recreate than a 100 story office block or a major airport, many or our ancestors during this period where still semi nomadic and often moved villages any why to follow herds.

But then as usual you weren't looking for a real answer, but a quick denier rant about politics.

It is an estimate. Some scientists say that that amount of warming will trigger dangerous feedbacks.

But, unless you believe computer models, those dangerous feedbacks could happen with less than 2C of warming.

It's a nice round number, nothing more.

None of "global warming" is a fact. It is all about the redistribution of wealth. Notice they don't use global warming anymore...but "climate change". The stupid thing is...THE CLIMATE ALWAYS changes...it has since the planet was formed. The sun provides 20,000 times the amount of energy humans use for any given time period...even a minor fluctuation of output from the sun can have huge effects on our planet.

Not that hard to find where it came from

http://www.realclimate.org/index.php/arc...

It's certainly not a "scientific fact", but I don't think anyone claimed it was.

It's a target to avoid bad things happening.

neither.