The effects of increasing greenhouse gas emissions

Our planet’s atmosphere is currently warming at a rate above that which might be expected from natural forcing, and the consensus of scientific opinion is that human activity is most likely responsible, through so-called anthropogenic forcing. The latter is generally defined as being primarily the result of two activities: human-generated emission of GHGs, more particularly CO₂, and deforestation, which reduces the size of the available carbon sink.

Many scientists, largely through the auspices of the Intergovernmental Panel on Climate Change (IPCC), have expressed concerns that warming of the atmosphere relative to its state in the pre-industrial era will lead to changes in climate at global, continental, national, regional and local scale, and in some cases these changes might have significant environmental, economic and social impacts.

Averting global warming through greenhouse gas reduction

The IPCC fourth assessment report concluded that a reduction in greenhouse gases (GHG) emissions is necessary to stabilise the concentration of GHGs in the atmosphere to avoid irreversible damage to the environment. In this respect it has been recommended that the rise in global average temperature, relative to pre-industrial levels, should be kept to below 2ºC.

In order to achieve this, it is estimated by the IPCC, in its best-case scenario, that the CO₂ concentration in the atmosphere should be stabilised at 350-400ppm and that this can be achieved if emissions peak before 2015 and are reduced by 50-85% by 2050 compared to 2000.

Even in this case, 30% of all plant and animal species will be at increased risk of extinction, two billion people worldwide will face increased water stress, and the world will face a number of other significant challenges.

How viable are these reduction targets?

The year 2015 is only seven years away, six years after Conference of Parties 15 (COP15) in Copenhagen and three years after any post-Kyoto Protocol agreement would come into force.

Given that the global annual mean concentration of CO₂ in the atmosphere is currently 383ppm and there has been a 34% growth in annual global CO₂ emissions over the last fourteen years, is it possible to achieve a peak in emissions before 2015 and stay below a global annual mean CO₂ concentration of 400ppm? If not, what should we do about it?