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ISSUE 2

Article 1a

Accelerated Global Warming and Atmospheric CO2 Emissions

 

An assessment of the likely increase of CO2 in the atmosphere due to climate change and if the Amazon Rainforest ceases to be a CO2 sink.

The C02 content of the atmosphere is usually expressed in parts per million (ppm) by weight and the use of fossil fuels is expressed as so many tons of carbon burned per year. At present the burning of fossil fuels releases 7 billion tons of carbon into the atmosphere each year in the form of carbon dioxide gas, C02.

C02 weighs 44 / 12 times the weight of carbon. This is derived from the atomic weights
of carbon, 12, and oxygen, 16. The molecular weight (MW) of C02 is 12 + (2 x 16) = 44 and the MW of carbon is 12. So C02 is 44/12 = 3.67 times heavier than carbon per molecule.

Therefore burning one billion tons of carbon produces 3.67 billion tons of C02.

(A) and so burning 7 billion tons of carbon will produce 26.7 billion tons of C02

The weight of the Earth's atmosphere can be calculated as follows. Atmospheric pressure at sea level is on average 14.5 pounds per square inch = 10 tons per square metre. This pressure is due to the weight of atmosphere above an area at sea level of one square metre.

The radius of the Earth "r" is 5,925 km and so the surface area of the Earth (land and ocean) is 4 x "pie" x "r" squared = 4 x 3.142 x 5925 x 5925 = 441 million square kilometres = 441,000 billion square metres.

Therefore the weight of the Earth's atmosphere is 441,000 billion x 10 = 4.41 million billion tons.

Now 26.7 billion (the weight in tons of CO2 emitted into the atmosphere each year, see (A) above), divided by 4.41 million billion gives the fraction 6 /one million which means that the CO2 emitted to the atmosphere each year from burning fossil fuels is equal to 6 parts per million (ppm) of the atmosphere by weight. (6 millionths)

It can be seen therefore that burning 7 billion tons of carbon from fossil fuels is now dumping 6 ppm per year of C02 into the atmosphere.

(B) Pro-rata, burning one billion tons of carbon from fossil fuels dumps 6 / 7 = 0.85 ppm of CO2 into the atmosphere.

As explained in the above Article 1, the Amazon rainforest is probably absorbing 2 billion tons of carbon per year. Removing this amount of carbon reduces the C02 content of the atmosphere by 2 x 0.85 = 1.7 ppm. per year.

So the Amazon rain forest is absorbing 1.7 ppm of the 6 ppm of the total C02 being emitted by fossil fuel burning.

The current understanding is that at the present level of concentration of C02 in the atmosphere C02 is being absorbed by natural processes, of which the Amazon rainforest is a major component, at the rate of 3 ppm, i.e. one half of 6 ppm rate at which CO2 is being dumped into the atmosphere from fossil fuel burning. If C02 emissions are rising this will mean that year on year the C02 content of the atmosphere will rise by at least one half the previous year's rate of emission.

Therefore at present C02 is increasing by 3 ppm each year (i.e. 6 - 3 = 3 ppm). If the level of fossil fuel burning rises by say only 25% (a much bigger rise is predicted) and if natural processes do not increase their rate of absorption then the rate of increase will become 3 + 25% of 6 = 4.5 ppm per year and if by 2050 we loose the absorption by the Amazon rainforest the rate of increase becomes 4.5 + 1.7 = 6.2 ppm per year, twice the current level. At this rate C02 levels would increase by 50 x 6 = 300 ppm during the 50 years from 2050 to the end of the century.

The increase in C02 at today's rate over the 50 years from now to 2050 gives a further increase of 50 x 3 = 150 ppm.

So the C02 content of the atmosphere by 2050 and 2100 could be as follows:

Today's level in say year 2,000

Increase at today's rate up to 2050 = 50 years x 3 ppm

Increase from 2050 to 2100 assuming 25% growth
in fossil fuel use and the Amazon rainforest
ceasing to be a C02 sink = 50 years x 6 ppm


Therefore total C02 in the atmosphere at 2100

= 350 ppm

= 150 ppm

 

= 300 ppm

 

= 800 ppm

This total does not include C02 from Amazon rainforest fires, however no doubt other forests will expand elsewhere in the world as their conditions become more favourable so release of carbon by forest fires in the Amazon rainforest will be offset by new trees elsewhere but there will be a time lag. Also non-tropical forests only absorb CO2 during the spring and summer growing season whereas tropical forests grow all the year round and tropical forests grow at a faster rate and so absorb more CO2 than temperate forests.

If 10 years' growth of the Amazon rainforest were released in one year's fires this would add an additional 10 x 1.7 = 17 ppm C02 into the atmosphere in that year.

If the Amazon rainforest becomes savannah then 90% of the carbon currently locked up in bio-mass would be released. Can we estimate how much carbon this represents?

Assume trees at 20 metre spacing, therefore 5 x 5 = 25 trees per hectare. (100m x 100m)
Assume 10 tons of carbon per tree, therefore 25 x 10 = 250 tons of carbon per hectare.

1 square km = 100 hectares. Therefore weight of carbon = 25,000 tons / sq. km.

The total area of the Amazon rainforest = 4,000,000 sq. kms. approx.

Therefore weight of carbon in trees = 25,000 x 4,000,000 = 100 billion tons

If 90% of this carbon returns to the atmosphere as CO2 this would increase atmospheric CO2 by 0.9 x 100 x 0.85 (see (B) above) = 76 ppm.

The increases in atmospheric CO2 levels described above are significant increases when compared to historic levels (280 ppm in 1850 and 170ppm.in the recent geological past) and also the rate of change is accelerating. We are entering unknown territory. However we can project what might happen on the basis of what we do know and the possibilities are awesome. These possibilities will be described in future articles to be published soon.

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