I don’t have time at the moment to put any figures around what i’m about to write about, but if someone feels like doing so, please go for it (likewise if you can point out any papers or books which have covered this issue).
So, what is it that I am going to write about. Well, in looking at the issue of green house gas emissions and the relationship to global warming, forestry frequently comes up. Given the sequestration benefits which forests provide, a way to tackle climate change has been to a) slow deforestation of existing forests, b) carry out reforestation of areas cleared.
Now, an issue which occurs to me is that, this problem is multi pronged. Let us cast our minds back to pre industrial revolution times, lets start at 1800 for arguments sake. So, at this point in time, we had a certain percentage of the earth covered in forests, providing their sequestration and carbon storage benefits. Trees grow and die, releasing and re-capturing carbon in the process, this carbon was all – excuse my lack of scientific eloquence here, this is a work in progress – above ground carbon.
So, we have that base state, with a relatively stable amount of carbon in the atmosphere/earth system continually being cycled through a process of sequestration-emission-sequestration. Now, things get interesting once the industrial revolution kicks off in earnest. Firstly, we have massive amounts of deforestation to feed industrial processes, beginning at the start of the 1800s. This reduces the number of trees participating in this sequestraion-emission cycle. The result, a net increase in emissions as trees are removed from this process. Consider this the ‘left punch’.
The ‘right punch’ comes around the beginning of the 1900s and accelerates with particular voracity from the 1950s onwards. This takes the form of fossil fuel related emissions. These are in effect carbon/green house gases which were previously not part of the atmospheric/earth system and were locked away under ground. By extracting and processing these, resulting in emissions into the atmosphere, we add to the volume of green house gases in this system.
The result here, combining these two factors is that, a) greater concentrations of GHG in atmosphere from deforestation with fewer trees to sequester carbon, b) even greater concentrations of GHG in atmosphere due to new inputs into atmosphere from fossil fuels.
What is the point of all this? The point – and the issue as I see it – is that, to reduce climatic conditions back to a natural cycle representing a state with minimal anthropogenic influences, we need two things. 1) Forest coverage to be returned to pre-industrial revolution areas, 2) removal of net increases in GHG as a result of fossil fuel combustion since 1900. OR in fact, potential – and contentiously – a third option, being, to offset any climatic impacts with global scale abatement methods (giant sun ray deflecting mirrors anyone?).
I have no definite conclusions regarding these thoughts yet, just some things to ponder on and consider when people talk about reducing GHG emissions and atmospheric concentrations.