This is the discussion thread for the Climate Change (explained) thread. Please hold off until I have actually fleshed out the main headings.

Hasn't the cooling after the War (at a time when CO2 emissions were rising), been attributed to industrial pollution by the warmist camp also?

Soren wrote:

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It wasn't a very good scientific reference, Soren. It's 'arse about' as the "lower classes might say"(not my saying). Generally sunspots are associated with flares. The more sunspots you have, the higher the effect on solar activity, but the actual effect is very limited. It only changes solar irradiance by a factor of 0.01%.

Astronimers (sic) are definitely not baffled - at least they would certainly be baffled by that very pseudoscientific claptrap that you quoted.

Well - if you look past the actual headings, I have expanded the headings into individual discussions.

You ask - how much is the actual contribution. Well the graph on post 4 of the sticky thread explains that better than I can.

Some forcings have a negative (cooling) effect, such as aerosols - in other words soot etc.  Some forcings are positive (warming).

The main input is of course, the sun.

I might leave it at that. I'm in the middle of packing, and I really want to write up some more on the Climate Change explained thread before I go.

Those questions are too hard to answer for someone who believes in global warming Soren - especially the question about using early evidence of the earth's climate changes. I still can't even figure out Muso's graphs - they span such a short period.

Atmospheric temperature has remained almost unchanged, although it may now be decreasing - hence the scientists have come to the conclusion that we're in for a cooling period.

Ground temperature is how they base their theory on man made global warming. This is increasing due to the continual logging and increased development/overpopulation- which is also why carbon dioxide levels are increasing.

I suppose while we're alive and breathing - this must be the right temperature for earth. Nature will determine when this planet is no longer sustainable for us humans and there's nothing we can do about it. Certainly an ETS isn't going to do anything, except line pockets. It's about time we seriously considered global population control.

What is the right carbon dioxide content of the atmosphere?

Actually it's more a question of what can we reasonably achieve in order to reduce the risk of considerable social and economic disruption.

I will answer the original question, but first I'll provide an explanation of the answer. Let's put the focus fairly and squarely on to human habitation of the Earth. The whole problem is a question of human survival. If we fail to reduce carbon emissions to such a level that will prevent global mean temperatures from increasing 2 degrees C, an enormous human tragedy on an unprecedented scale will start to unfold.

First, we must look at the very lengthy history of this planet.

The Earth is approximately 4.5 billion years old, however, human beings have been on the planet for only 0.004% of that history; modern Homo sapiens evolved around 200,000 years ago. Dramatic climate changes have indeed occurred in the Earth’s long history. Early humans experienced, and a fraction of them survived, some of these dramatic climate events.

However, only during the last 12,000 years, a period in which the Earth’s climate has been comparatively warm and stable, have humans really thrived.

The scientific evidence today overwhelmingly indicates that allowing the emission of greenhouse gases from human activities to continue
unchecked constitutes a significant threat to the well-being and continued development of contemporary society. The knowledge that human activities are influencing the climate gives contemporary society the responsibility to act. It necessitates redefinition of humanity’s relationship with the Earth and for the sake of the well-being of society,  it requires management of those human activities that interfere with the climate.

Let's get back to the original question of what is the right, or optimum carbon dioxide content of the atmosphere. Well a simplistic answer to that is what would the atmospheric CO2 concentration be today if the fossil fuel combustion had not occurred. The answer is round about 200ppm. At that level, there would certainly be no impending crisis.

Clearly that's quite an optimistic target. To set a more realistic target  requires recognition of the various risks that present themselves as the atmospheric concentration of CO2 increases. These are Social and economic disruptions that will occur on our best knowledge as the effects of increasing atmospheric CO2 start to take effect.

The risk assessment takes into account such things as increasing ocean levels, the effects on major food crops, the effects on ocean ecosystems and food chains - particularly for economically important species.    

Obviously it is not possible to stop all polluting activities immediately. The economic effects on the world would be enormous, so we arrive at a compromise of limiting the temperature rsie to 2 degrees C.

Of course the ultimate answer is a gradual decarbonisation of the world economy to the stage where we no longer have to rely on fossil fuels.  

The global carbon dioxide level corresponding to that 2 degrees C 'guardrail' is around 450ppm CO2 equivalents.

To provide a more rigorous explanation, atmospheric CO2 concentration should not exceed 400 ppm CO2 if the global temperature rise is to be kept within 2.0 – 2.4°C. Today, the CO2 concentration is around 385ppm, and is rising by 2 ppm per year. The 2007 concentration of all greenhouse gases, both CO2 and non-CO2 gases, was about 463 ppm CO2-equivalents. Adjusting this concentration for the cooling effects of aerosols yields a CO2-equivalent concentration of 396 ppm. A recent study estimates that a concentration of 450 ppm CO2-equivalents (including the cooling effect of aerosols) would give a 50-50 chance of limiting the temperature rise to 2°C or less.


What is the right temperature for the Earth?

Using the explanation above, we're talking about 2 degrees above pre-industrial temperatures. Again it's a question of what can we reasonably achieve to reduce the risk of considerable social and economic disruption.

How should enormous economic pain be imposed?

Well if you want the maximum economic pain to be imposed, simply do nothing.

It's probably best to quote directly from the Copenhagen Synthesis Report which gives a fairly detailed Economic Synopsis:

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Why have climate models not been run backwards to replicate all we know?

That's a pretty stupid question actually. I'll come back to it if anybody is really interested, but it demonstrates a total ignorance of the laws of thermodynamics.