What are the calculations?

Especially since the news are reporting that we've passed the milestone after which global warming of at least 2 Celsuis can't be avoided. I wonder if he considered the clathrates, the methane in the permafrost and the rotting of the pine trees from the pine beetles.

There's no indication that the climate would return to the same stable point considering we were in the least stable of the three climatic stable points ( snowball earth, warm earth and ice age earth, we're hopefully still in the ice age earth ).

The calculations are too long to fit on here so all I can do is start you off and leave you to finish.

First we need a starting point and an end point. We’ll use 1980 as the starting point as this is when global warming kicked off and we’ll use the present as the end point.

Next we need to see how 1980 differs from 2013 in terms of atmospheric composition and average global temperature. This is where it gets long winded because you need to perform the following calculation for each and every greenhouse gas in the atmosphere.

For each greenhouse gas you need to know the following…

• Volumetric concentration in 1980

• Volumetric concentration in 2013

From that you can work out what increase or decrease there has been.

Next you need to calculate the global warming potential of each of the greenhouse gases. These data are readily available although most sources state 25, 50, 100 and 500 year GWP’s. On that basis you may want to change the start date from 1980 to 1988 to make the maths easier, alternatively interpolate between the 25 and 50 year values to get the 33 year GWP (note, you can’t simply divide the 100 year GWP by 3 as potential is not linearly related to time, hence interpolation isn’t ideal either).

Note that GWP is measured relevant to CO2 which is assigned a fixed value of 1.000.

Next you need to look up the atmospheric residence period (ARP) of each of the greenhouse gases then you need to apportion the GWP as a ratio of timeframe:ARP. If the ARP was 33 years and the timeframe was 1980 to 2013 then the apportionment would be 100%, similarly if the ARP was 165 years then the apportionment would be 20%.

In effect what you will have now is a long list of greenhouse gases and next to them a list of numbers representing how much of their total warming capability will have been imparted across the timeframe in question (33 years in this example).

Then you need apply this figure to the ratio change in volumetric concentrations and repeat this for every one of the greenhouse gases.

Once you’ve done that you will effectively have a list of ‘ingredients’ that collectively cause X degrees of global warming. Something like “2 carbon dioxides plus 3 methanes = 1°C of warming”.

All that this has done is to get the numbers needed for the next part of the equation.

Now you need a snapshot of the current atmosphere, that will tell you exactly what’s in it. From this you can calculate that the current concentration of gas A will cause B amount of warming over C years, and that gas D will cause E amount of warming over F years.

This would give you an approximation only and you could if you wanted apply a linear decrease in respect of each gas to the warming starting from the present to the time when the GWP of each gas falls to zero or the ARP expires. You could then add up the total amount of warming that would happen in each year until either a steady state was reached (this would be after 8,500 years) or a pre-determined time had elapses (probably something more sensible such as by the end of the century or the next 200 years).

If you wanted to be more accurate then you would need to run the calculations X number of times where X is the ARP and you would assign the GWP to each year.

The reason I said previously that you need a spreadsheet is because there are literally millions of calculations that are needed. You could of course simplify it by concentrating on just a few of greenhouse gases – four of them make up 99% of all GHG’s so you can get an accurate enough figure using carbon dioxide, methane, nitrogen dioxide and dichlorodifluoromethane.

You’ll find enough info on the website below to allow for a reasonably accurate calculation:

http://www2.mst.dk/common/Udgivramme/Frame.asp?pg=...

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RE: YOUR ADDED DETAILS

I do know what a differential equation is. I don’t particularly like them and tend to avoid using them – just as I have in this question; therefore I fail to see why your comment has any relevance. You asked how I did the calculation, I told you how I did it, if you would have done it differently then that’s perfectly OK.

It proves all along, you were wrong eight years ago and haven't advance in knowledge in all that time. Are you really proud of it?

Ha! I think "I did this estimation ..." would be a lot more like it... Just sayin'...

http://onlinelibrary.wiley.com/doi/10.1029/2010GL0...