Carbon is one of the most abundant elements in the Universe. It is the basis of all organic substances, from fossil fuels to human cells. On Earth, carbon is continually on the move – cycling through living things, the land, ocean, atmosphere, and even the Earth’s interior. In some areas it moves quickly, in others it takes eons. The fast part of the cycle includes us – from birth to death and decomposition in perhaps 80 years – whereas carbon locked in marine sediments may remain undisturbed for millions of years.
What happens when humans start driving the carbon cycle? We have seen that we can make a serious impact – rapidly raising the level of carbon in the atmosphere. But we really have no idea what we are doing. At the moment we don’t even know what happens to all the carbon we release from burning fossil fuel. Obviously a lot of it goes into the atmosphere, but every year we loose track of between 15 and 30% (NASA). Scientists speculate that it is taken up by land vegetation, but no one really knows. This sort of uncertainty makes it doubly difficult to predict the outcome of tampering with something as complex as the carbon cycle.
It’s killed before, will it kill again?
The amount of carbon released from burning fossil fuels is nothing compared to what might be in store for us. Lying at the bottom of the oceans and buried in the Arctic permafrost, are huge quantities of frozen methane. These “gas hydrates” are kept solid by the combination of low temperature and high pressure. Estimates suggest that there is almost twice the amount of carbon stored in this frozen reservoir than found in all known fossil fuel reserves (USGS). Increasing atmospheric and ocean temperatures could destabilise the hydrates, allowing the release of methane – a greenhouse gas, 21 times more potent than CO2. As more methane is released, temperatures climb further, releasing even more gas and driving the system into a runaway catastrophe.
Despite the evidence of global warming and the known greenhouse characteristics of methane, interest in gas hydrates as a potential energy source continues to accelerate. Many governments, such as the U.S., Japan, Korea, Canada, India, Norway and Australia are actively funding research programes. Japan has been the most active, drilling two off-shore exploration wells.
Uncontrollable global warming may seem unlikely, but scientists are increasingly convinced it has happened before. During the Permian, 250 million years ago, volcanoes in Siberia spewed masses of carbon dioxide into the atmosphere. The global warming that is thought to have ensued, is the prime suspect in the greatest mass extinction of all time – wiping out 95% of all life forms on the planet. Evidence from rocks suggests that temperatures during this time rose by 5°C – one of the IPCC scenarios predicts that we could see a 6°C increase by the end of the century.
The carbon storage
Greenhouse gases have been present naturally in the atmosphere for millions of years, but the age of industrialisation has interfered in the natural balance between generating greenhouse gases and the natural sinks that have the capability of destroying or removing the gasses.
Forests are a major reservoir of carbon, containing some 80% of all the carbon stored in land vegetation, and about 40% of the carbon residing in soils. Forests also directly affect climate on the local, regional and continental scales by influencing ground temperature, surface roughness, cloud formation and precipitation.