[dentstudent (OP)]

You may have seen in the thread "Climate Change and the Public" a discussion about amelioration of GHG's amongst other things. It arises for various reasons, as George rightly points out, that there is no target. Other than those set by industry to reduce emissions for example Kyoto (and which are just that, percentage reductions, not ppm targets) there appear to be no guidelines for future conditions. There is untold coverage of what we should be doing to reduce C output, to improve sequestration and so on, but to what end?

Of course it is nigh on impossible to put a figure on perceived acceptable temperature increases or GHG levels, which makes it all the more difficult.

Therefore my question is: What are we actually aiming for?

[JimBob]

It is a question for politicians and, being politicians, they will never agree on what to do. It is most difficult when a country such a s the IS decides not even to show up for the Kyoto conference.

THAT is absurd.

[another_someone]

It is a question for politicians and, being politicians, they will never agree on what to do.

There are two questions - what is desirable, which is a question for politicians; and what is possible, which politicians cannot answer.

The first question is, what targets are achievable?  No amount of political competence (assuming that is not an oxymoron) will give that information.

[another_someone]

OK, let me put the discussion dentstudent and I were having on a more concrete footing.

Say we were to decide that we wished global annual average temperatures not to rise more than 1 degree Celsius above 1980 level, nor fall more than 2 degrees below that level.  In that case, what levels of atmospheric CO₂ are appropriate to achieve that end.

Given that we have set targets for atmospheric carbon emissions by the Kyoto treaty (assuming the treaty achieved its objective - and whether that is achieved is indeed a political rather than a scientific matter, and as we are dealing with only the science, we shall assume it is achieved), then what is the targeted range of temperatures that is believed to be achieved by that treaty, and how much does that differ from the range of temperatures that would happen in the absence of Kyoto?

Going further than that.  Assuming there were no political impediments, then what is the ultimately desirable range of global temperatures we should be seeking to achieve, and what are the levels of global CO₂ that is believed to be needed to achieve that end, and is that end even achievable by simply manipulating CO₂ (or even other atmospheric carbon emissions) levels alone?

[dentstudent (OP)]

OK. This seems to have stalled somewhat.

I'll put up a notional target for what I think might be a good start point, and we can discuss from there.

I just want to discuss the human influence for now. I'm aware of the holes in the numbers, but just for starters......

If we can classify all the anthropogenically added CO₂ as coming from fossil fuels (coal, gas, oil), is it possible to determine the net CO₂ output that we have emitted? I don't think it's simply going to be: coal+gas+oil burned  * CO₂ content per tonne = additional CO₂, but can we provide a rough guide as to how much more has been added compared to if we had been using renewable fuels instead. (But what kind of renewable etc etc? I don't know, but let's pretend that it was CO₂ neutral). This difference might provide an indicator for how much CO₂ should be sequestered, or perhaps an idea of how many ppm CO₂ there would be with human intervention removed. In fact, that's probably a much simpler way of looking at it (though not necessarily any easier to answer):

What would the CO₂ content of the atmosphere be without our emissions?

[another_someone]

OK. This seems to have stalled somewhat.

I'll put up a notional target for what I think might be a good start point, and we can discuss from there.

I just want to discuss the human influence for now. I'm aware of the holes in the numbers, but just for starters......

If we can classify all the anthropogenically added CO₂ as coming from fossil fuels (coal, gas, oil), is it possible to determine the net CO₂ output that we have emitted? I don't think it's simply going to be: coal+gas+oil burned  * CO₂ content per tonne = additional CO₂, but can we provide a rough guide as to how much more has been added compared to if we had been using renewable fuels instead. (But what kind of renewable etc etc? I don't know, but let's pretend that it was CO₂ neutral). This difference might provide an indicator for how much CO₂ should be sequestered, or perhaps an idea of how many ppm CO₂ there would be with human intervention removed. In fact, that's probably a much simpler way of looking at it (though not necessarily any easier to answer):

What would the CO₂ content of the atmosphere be without our emissions?

Only if you have two Earth's, and run an experiment side by side, one with humans and one without, and look at the CO₂ levels of the two planets.

As you say, we can look at how much fossil fuel we have burnt (although it is much more difficult to judge how much wood is burnt, because this is outside of the large industries which are the easier to monitor).  The trouble is trying to asses what impact we have had on other flora and fauna (both on changes in the levels of photosynthesis, and the levels of CO₂ production by microbes, insects, and other animals).

We can draw graphs, and make simple extrapolations of historic graphs (which of often dependent on proxy, or highly localised, measurements), and judge where the present deviates from that simple extrapolation, but who is to say that the simple extrapolation was ever accurate?

There is no real sanity check on whatever theory we have about human impact upon the world, because there is no comparable world without humans.

[another_someone]

If we can classify all the anthropogenically added CO₂ as coming from fossil fuels (coal, gas, oil), is it possible to determine the net CO₂ output that we have emitted?

http://news.bbc.co.uk/1/hi/sci/tech/6904249.stm

This year could see the biggest "dead zone" since records began form in the waters of the Gulf of Mexico.

Scientists say conditions are right for the zone to exceed last summer's 6,662 sq miles (17,255 sq km).

The dead zone is an area of water virtually devoid of oxygen which cannot support marine life.

It is caused by nutrients such as fertilisers flowing into the Gulf, stimulating the growth of algae which absorbs the available oxygen.

The volume of nutrients flowing down rivers such as the Mississippi into the Gulf has tripled over the last 50 years.

The annual event has been blamed for shark attacks along the Gulf coast, as sharks, along with other highly mobile species, flee the inhospitable waters.

Animals which cannot move simply die.

Nutrient load

 "I am anticipating a historically large hypoxic (oxygen-deficient) zone this summer, because the nitrate loading this May, a critical month influencing the size of the area, was very high," said Eugene Turner from Louisiana State University.

"The relatively high nitrate loading may be due to more intensive farming of more land, including crops used for biofuels, unique weather patterns, or changing farming practices."

The nitrate load is so high that the dead zone may attain a size of 8,500 sq miles (22,015 sq km), almost double the average since 1990.

However, an active storm season could change that forecast, as storms mix the seas, dispersing nutrients and algae and bringing in oxygenated water.

Professor Turner is one of the scientists involved in modelling the dead zone, supported by the US National Oceanographic and Atmospheric Administration (Noaa).

The United Nations warns that dead zones are becoming more common globally as intensive agriculture spreads.

Its 2003 Global Environment Outlook said that the number of seasonal hypoxic areas has doubled each decade since the 1960s.

The UN believes the algal blooms are having a significant impact on commercially valuable fish stocks.

It occured to me that if all of this oxygen is being consumed, would it not be reasonable to suppose that the major portion of it is being converted to CO₂.  So the question is, given that this CO₂ is generated algae, but is stimulated to human action, would you class this as anthropogenic CO₂?  It certainly is outside the remit of Kyoto.