User talk:KimDabelsteinPetersen/CO2 increase

FAQ: Is the increase in CO2 manmade?
Yes it is - this is as close to absolute certainty as things can be in physical science.

How can we say this?

Well there is actually several lines of evidence - lets go through them:

Simple accounting (second order evidence)
The first one is simple accounting. We know how much carbon (as fossile fuels) that we've burned since the beginning of the industrial revolution. The total amount comes to around twice as much as the increase in atmospheric CO2. (we'll get into where the last part went - when we get further on in this debate).

Carbon isotopes (first order evidence)
The second one is based upon measurements of carbon (C-12) and its isotopes (C-14 and C-13) in the atmosphere. (called the Suess effect) :

Carbon-14 is created in the upper troposphere by high-energy reactions created by cosmic rays - Carbon-14 is radioactive and has a half-life of 5730±40 years. Oil, coal and other fossil material has no carbon-14 content (its decayed away over millions of years) - so when we burn the fossil material it releases carbon with no C14 content. This means that the amount of C14 in the atmosphere should fall - and it does.

Carbon-13 has the strange characteristic that plants do not particularly "like it", so when plants use CO2 in photosynthesis, they avoid the C13. This means that plant-material is consisting almost completely of C12 - and for the same reason, oil, coal and other fossil material contain almost no C13. So when we burn it - we'll see the same effect as for C14: The relative abundance of (C12,C13,C14) changes.

These two (C13,C14) and their relative abundance work as a fingerprint as to where the carbon is coming from.

Plantmaterial - has low levels of C13, but normal levels of C12,C14 Ocean dissolved CO2 - has normal levels of C12,C13 (normal levels of C14 - but could be low if the CO2 came from the bottom (ie. old storage). Fossil material - has low levels of C13,C14 (almost pure C12).

So when the atmospheric level of C13 and C14 falls (as measured) in proportion to C12 - then we can see that it comes from the burning of fossile fuels. (ie. the Suess effect).

Paleo-data (first order evidence)
This line of evidence is primarily inferred, during the last stable geological period (around 20 mio. years) - CO2 in the atmosphere has varied between 180ppm (the coldest parts of a glacial) and 300ppm (the warmest part of interglacials). We know this from several paleo sources - such as sediment-layers, ice-cores etc.

During the last 150 years (or since we started to burn fossil fuels) - the atmospheric content of CO2 has risen by around 35.7% from 280ppm (has been reasonably stable here for the last 20.000 years) - to currently around 380ppm.

Sinks and Sources (second order evidence)
This line of evidence is based upon tallying the various sources, and the various sinks of CO2 - what is calculated is the net sink or net sources. The ocean for instance is emitting CO2 - but is also sinking CO2 - by subtracting these fluxes, we can see how much the oceanic contribution to the carbon budget is.

When calculating this - we can see that the annual contribution to the atmosphere is around 2ppm (or 4.26 Gt CO2) - and we can also see that the only source where this can come from is from human (antropogenic) sources. Since nature as a whole is acting as a sink.

Oxygen content (first order evidence)
The last one is rather simple - When carbon is burned it oxidizes - that means that it uses 1 oxygenmolecules. So for each new carbon atom released - 2 oxygenatoms are used. This can be measured - since for each 100 atoms of fossil-fuel carbon burned, about 140 molecules of O2 are consumed

And it does. (to an extent)

Addendum here: The reason that this line of evidence is important, is that if the CO2 had come from the Oceans - the oxygenlevel would not fall. As the CO2 is released with oxygenmolecules from the oceans as well.

It would have been theoretically possible for the CO2 to come from the very bottom of the oceans (ie. large outgassings beyond what Henry's law could counteract (and thus elude us by still making the surface waters acidic)), which means that it could have been stored away for thousands of years, exibiting the same C14 depletion as fossile fuels, so that the oxygen level falls proportionally with CO2 increase - means that the CO2 couldn't originate in the oceans. (Nb. this wouldn't have the C13 signature seen though).

The same goes btw. for volcanoes - as these also release it as CO2 (ie. without oxygen from the atmosphere). This happens by metamorphism of basic earth materials. For instance Carbonates reacting with Quartz: CaCO3 + SiO2 = CO2 + CaSiO3. The Calcium Silicates (CaSiO3) come back out as lava adding to continental crust, and the CO2 comes out of the volcanos as explosive gas!