The amount of CO2 in the air has dramatic effects out of all proportion to the amount of the gas in the air or in proportion to the amount emitted by humans. It produces a non-linear effect.
Concentrations of CO2 have been much greater than they are now, in times when there were no humans around. Nobody is arguing that the world would end with much higher CO2 levels, just that relative climate stability would end, as the climate system shifts into new patterns, and human civilization would be extremely likely to suffer significant disruption and possibly destruction depending on how bad it gets.
As far as we can tell for the last half million years or so CO2 levels have remained between 180 and 300 parts per million (again, that’s pretty low compared to some other geological periods). In the last 100 years or so, this has risen to about to 410 parts per million (people were hoping the rise would stop at 350 parts per million, but it hasn’t).
There is no indication that this increase in CO2 concentration is slowing. That is a pretty rapid and significant change and most of it seems to have come from human emissions. The theory of greenhouse gases which has been around for well over 100 years would lead us to expect a rise in global average temperatures as a result, and this is happening – and it is happening pretty much as predicted (although a bit higher and more rapid than some official predictions).
Again it needs to be said that the average temperature rises are relatively small, but these small rises appear to be disrupting climate stability already. What seems small to us can have large effects on the system as a whole.
Now natural emissions of CO2 are huge – figures usually suggest around 800 giga tonnes per year. Natural ‘carbon sinks’ and conversion processes handle these emissions quite well. Human emissions are much, much, less than that, even now about 30 giga tonnes per year but increasing.
You might think its a matter of common sense that this little overshoot would not make that much of a difference, but we are not dealing with a simple linear system here. Small changes (in CO2 levels and temperature) can make large differences, due to the way feedback loops work and trigger, or disrupt, other systems.
For some while these emissions made little difference because natural carbon sinks could deal with the extra burdens – these sinks produced the well known pause in the rate of increase of average temperature (not a decrease in temperature or even a stabilizing of temperature, but a decrease in acceleration of temperature increase). These now seem to have been used up. The more we destroy the ecology and engage in deforestation etc. then the worse the accumulation gets and the higher the temperature increases. The rapidity of the change together with environmental destruction renders natural evolutionary or adaptational processes irrelevant – natural sinks do not appear to be able to handle the increase any more.
The more that the average temperature increases, the more that some natural sinks will start releasing CO2, methane and other greenhouse gases. For example the Russian Steppes might already be releasing previously frozen methane for more green house emissions.
This makes the situation even worse; it compounds the problems and shifts them into a whole other realm. We have to stop temperature increases now, if we don’t want extreme weather events to become more and more common, and remediation to become more difficult than it already is. Also as you probably know, land ice is melting and glaciers are disappearing and this will also likely lead to temperature increases and to rising sea levels. Neither of which is good for coastal cities or for human water supplies.
So if we continue with our current patterns of CO2 emissions we are heading for likely catastrophe – we are certainly not heading for good times.
This whole process is difficult to predict in its entirety, because of the way local conditions act with global conditions. For example, higher average temperatures could disrupt the patterns of the Gulf Stream which has kept the UK relatively warm. If the Gulf stream moves southward, then parts of Europe could heat up while the UK’s average temperature lowers. Whatever, happens the weather will change and probably change violently. If we do not stabilize CO2 emissions then the system fluctuations will get wilder, as it is subject to greater stress.
We need to stop CO2 emissions as quickly as possible, and start protecting the rest of the environment to allow its resilience to function. So we have to stop massive deforestation and other forms of pollution as well as stop CO2 emissions.
Human CO2 emissions largely come from burning fossil fuels, some forms of agriculture, and with some from building (concrete use). For some reason official figures for fossil fuel emissions often split the burning into electricity production, transport, industry, domestic and so on, but they all have the same cause.
We can pretty much end coal fired power for electricity now if we put money into it and impose regulations bringing coal burning to an end. We are helped in this as building new coal fired power stations is becoming more expensive than renewables, even with all the subsidies that fossil fuel mining and power receives. Ending coal burning won’t necessarily be pretty, but it can be done. Coal is poisonous during the mining and during the burning, and devastates fertile land during mining, so its a good thing on the whole. Petrol/oil burning may be a bit more difficult. We need an excess of renewable power and storage to allow transport to work like it does now. Possibly generating hydrogen from water is one way around that, but we need heaps of excess renewables to do that and that may then come up against material limits. Changing agriculture will be more difficult still, but people are claiming low emissions concrete is becoming available (I’m not sure).
However, there is a problem, even if we could stop tomorrow. The natural carbon sinks are over-stretched and unlikely to recover quickly. They will not remove the “excess” CO2 from the atmosphere quickly enough to prevent already dangerous average temperature increases. We may need to research Carbon dioxide removal techniques as well. These are being developed, but more money for research is needed, and we need to find some way to dispose of the extracted CO2, so it is not returned to the atmosphere in a couple of years. This is a massive technical problem, which is not really close to being solved (that is a matter of argument, but that is my opinion). Hopefully the problem can be solved.
We need to cut back emissions quickly. We will then almost certainly need to develop an extraction technology. If we can’t do either of these, then we face truly massive disruption: more extreme weather, flooding, city destruction, people movements, food shortages, and warfare.
Climate, technology and chaos Blog 