We can still do something about the overall level of climate change if we act now, take bolder actions and leave the coal in the ground.
A lot of information was provided to us and I am going to put together a few blog posts covering some of it. This one is about the carbon uptake by the oceans.
Humans have impacted the earth's carbon cycle by mining some of the carbon in the solid earth reservoir and putting it into the atmosphere as carbon dioxide (CO2) at a rate of about 8 gigatons per year. We are also cutting down trees on land, which results in about another 2 gigatons a year going into the atmosphere. (One way to think of a gigaton is that all of the people on Earth probably weigh less than a gigaton). The amount of CO2 in the atmosphere is going up but it's not going up as quickly as it should be for the amount of carbon we're putting into it. It's only going up at about four or five gigatons per year. This 'missing' carbon that we're putting in the atmosphere is being taken up by a combination of the land and the ocean. The time scale for solid earth to take up carbon is very long and it is hard to measure how much carbon is going into the land but we can measure the carbon uptake in the ocean much more easily and precisely.
How much CO2 is going into the oceans?
How much CO2 is invading the oceans can be measured by a variety of different techniques. One involves measuring simultaneous changes in atmospheric CO2 and oxygen. When you burn fossil fuel it consumes oxygen and so the CO2 concentration goes up and the oxygen concentration goes down. There are two different possible fates for that CO2:
- It could get taken up by trees on land by some photosynthesis. When that happens it releases oxygen.
- It can just dissolve in water and does buffer chemistry so it doesn't immediately get turned into photosynthesis. It doesn't produce oxygen.
There is 40 times more carbon dioxide in the ocean than in the atmosphere and the reason why the ocean doesn't immediately mop up all of our extra CO2 is because of the way the ocean water circulates. In the high latitudes, in Antarctica and in the North Atlantic, where it gets very cold, the water at the surface gets cold and sinks by convection giving a very focused downward flow in very specific locations. This is balanced by upward movements in other parts of the ocean. The overall time scale for the circulation of the ocean is about a 1000 years and that actually limits how quickly the CO2 can equilibrate between the atmosphere and the ocean.
The chemistry of CO2 in the oceans.
So what happens to this CO2 when it is absorbed by the oceans? Well - nature strives towards equilibrium and thus for the ocean and the atmosphere to contain equal concentrations of CO2. When CO2 dissolves in sea water it does some interesting chemistry and carbonic acid is formed. The chemical reaction has multiple steps:
CO2 + H2O ⇔ H2CO3 ⇔ H+ + HCO3- ⇔ 2H+ + CO32-
Carbonic acid is a diprotic acid which means it can release first one H+ ion and then a second H+ ion to the water. When it releases its second proton it becomes a carbonate ion. The bicarbonate forms a buffer in the ocean and the existence of this chemical reaction allows the water to take up more CO2 than it would if there were no chemistry. There is ten times more of the carbonate ion than there is dissolved CO2 in the water which means the ability of the water to take up CO2 is ten times stronger than it would be if this chemistry didn’t exist.
The price of the ocean buffer.
However, as I stated before there is a price to be paid for this. That price being the depletion of the carbonate ion by this buffer chemistry has caused the ocean to become more acidic. This is known as ocean acidification and it is having a very detrimental impact on ocean life forms (particularly those that make calcium carbonate shells) and the food chains of the oceans.
More on ocean acidification...
photo credit: Storm Crypt via photopin cc