Carbon Sink Reversal
This is the most scary scenario of all, as it confounds the most popular current solution to global warming. Since Kyoto most of the industrially popular solutions, especially in Europe, have involved Carbon Offsets.
This program allows you to reduce your apparent carbon footprint by purchasing trees that will absorb what you produce, or commit to some low-emission enterprise in developing countries. In rainforests a tree can remove about 22 kg of CO2 each year. By the time a tree has reached full maturity it will have sequestered about 2000 pounds of CO2.
This is the theory. See Footnotes #2.
Investigations made ten years ago showed that raised levels of CO2 was stimulating trees to grow. Based on this, computer models of climate change assumed that existing forests could absorb 3 billion tons of carbon annually, even without new planting. The offset provisions of the Kyoto Treaty were founded on this assumption.
Such a happy, and economically pleasing, scenario is now known to be uncertain, if not false. When plants come under stress as temperatures rise the sugars trees make during photosynthesis release CO2 back into the air. Forests are then no longer carbon "sinks". They become a source.
In some areas this is now happening.
Trees are now becoming a source of atmospheric CO2.
When temperature rises above 1°C this will become a serous tipping point.
There will then be less and less benefit in planting trees.
WE WILL HAVE TO FIND OTHER SOLUTIONS.
This complicates the entire Kyoto campaign for offsetting carbon use against new planting. If we let temperatures go above one degree the benefit of planting trees decreases. We can no longer continue to emit carbon on the happy assumption that planting will make it OK.
When we add increased logging and forest fires to this equation, and the severe threats to the Amazon forests from changing rain precipitation, we KNOW WE ARE IN TROUBLE and that we have to find another way to deal with our problems.
The earth's soil is also a huge trap for carbon dioxide. Over the past 25 years the carbon content in soils of England and Wales has diminished by 13 million tons each year. Taken world-wide this figure is particularly unsettling, as there is some 300 times as much carbon trapped in the soils as we release each year from burning fossil fuels.
Finally, we need to realise that some degree of carbon sink reversal is now inevitable. Although global temperature increase has so far been less than 1°C, in the last three decades the rate of emissions have increased dramatically with the largest surge in industrial activity, vehicular traffic and mass logging of rainforests in history.
Even worse, heat-trapping emissions take time to build up their full effect as ocean temperatures are slow to catch up with the atmosphere. The best estimate is that there is a 25- to 30-year time-lag between greenhouse gases being released into the atmosphere and their full heat-trapping potential taking effect.
That effectively wipes out any feeling of comfort.
It means that most of the increase of 0.8˚C during the last century is not caused by current level of carbon dioxide but by what was already in the atmosphere in the 1970s. On top of the extra heat we are already experiencing there is another 30 years of ever-accelerating warming built into the climate system.
Even if we stop emitting now many forests will quite soon begin to emit more CO2 than they absorb. We have to go beyond the comforts of Kyoto to full governmental regulation that will penalise polluters (including car owners and airlines) and reward low impact technology.To the top