An easy solution to global warming?
Carbon offsetting is a widely, and vaguely, defined area. Generally it means that carbon emissions incurred in one place are offset by specific measures in another one. A popular example is the planting of trees to offset emissions incurred by e.g. long range flights or even events such as rock concerts.
While this seems like a straightforward and easy solution (plant a number of trees based on the estimated consumption of carbon during their life time, and the amount of emissions you want to offset), there are several catches. Firstly, staying with our example, when the trees die they emit the amount of carbon dioxide that they consumed during their life time. The benefit for the environment is thus nil. In order for the tree example to work, and the carbon emission balance to eventually turn positive, a whole forest would have to be planted and maintained "forever", or at least a very long time. It is doubtful that his kind of guarantee can be given for most projects or commercial offers of this kind.
What other ways of offsetting carbon are there?
Several measures at more or less advanced stages of development are available to reduce carbon emissions. Examples include:
Carbon sequestration from power plants, oil fields and coal mines: CO2 is extracted and subsequently injected into e.g. underwater sea beds or deep rock sediments, where it is expected to remain for a very long time. This approach is highly effective in theory, but in practice it is not yet applied on a wide range (technical difficulties and costs involved with extracting CO2 is a key factor here). In addition, the storage capacity of underwater fields and sediments is not fully researched, Also, in particular in the case of sediments, there is a risk of CO2 leaking back into the atmosphere over time.
Coal gasification: This process is generally applied in so-called "clean coal" power plants. Coal is gasified under very high temperatures into a "syngas", consisting mainly of hydrogen and carbon monoxide. The syngas is then burnt in a turbine that drives an electric generator. CO2 can be relatively easily isolated in this process, and subsequently sequestered. However, the process is not yet applied on a large scale, once again mainly because of cost factors. In general though this is a much cleaner way to produce energy from coal (traditional coal plants emit twice the amount of CO2 per unit of energy with respect to plants powered by natural gas). On the downside, coal gasification increases the cost of energy, bringing it close to the level of some forms of renewable energy.
Capturing of methane from coal mines that can be used to drive fuel cells and to produce energy: this is a good idea that works in practice. But it is only applicable to these specific cases (a small number of mines), and hence has a limited overall impact.
In summary, there is a wide range of applications and projects that can make sense from an overall ecological viewpoint. Each has to be analysed in detail to assess the effective reduction of CO2 emissions over the long term, as well as potential collateral effects on the environment and the population. No way exists today - and is unlikely to exist for many years to come - to easily offset carbon emissions on a large scale.
In addition, while the methods described above are potentially highly effective in reducing CO2 emissions from a specific plant or oil field, they come at a cost. This brings the price per energy unit produced almost to the level of renewable energies.
While this is not generally bad - higher energy prices lead to reduced consumption and are thus good for the environment - a lot of pressure is required to make e.g. plant operators adopt those clean technologies. The level of pressure required for a large scale adoption can probably only be exercised by some form of legislation or carbon tax. If global warming continues at the current pace, then it is highly likely that in 10 to 20 years from now the public pressure will be high enough to lead to the same effect. But then it might already be too late.
What is the solution?
Absolutely the best and most effective way to reduce carbon dioxide, as well as other damaging emissions, is not to produce them in the first place. Once carbon dioxide is in the atmosphere, it remains there for more than 200 years, making any kind of "extraction" complicated. Whereas on the other hand, there is an immense range of measure that everyone can apply in order to avoid incurring those emissions.
Everyone can contribute -- start by looking at the Sustainable Living chapter of this section, for instance, and continue on the resources section.