the science behind the problem

Over the past 20 years it has become increasingly evident that human activity is accelerating climate change. An enormous amount of research is being devoted to this topic which is reviewed periodically by the Intergovernmental Panel on Climate Change (IPCC). Their most recent assessment reflects the scientific consensus on climate change and its impacts.

Andean Landscape, Ecuador © Andrew Smiley

Essentially, climate is driven by the sun’s energy. How much energy remains in the earth system and how much is reflected back out into space depends on the composition of the atmosphere (of gases, clouds and particles) and the reflectivity of the surface. Changes in either will affect the energy balance, and so change the climate. This is a natural process and climate has always been changing – indeed, without the greenhouse effect whereby energy is trapped in the system and heats it up, the world would be too cold to inhabit. The problem is not the change itself but the speed with which it is happening, its impact on an environment already rendered fragile by human activity, and the fact that humanity is driving it.

The three main greenhouse gases are methane, nitrous oxide and, most importantly, carbon dioxide. The two main sources of CO2 are emissions from fossil fuel use and deforestation – one releasing carbon by burning ancient biomass and the other by burning its modern equivalent. CO2 concentrations are now far higher than at any time in the past 600,000 years and emissions continue at an accelerating rate. It is now clear (with more than 90% confidence) that they are warming the planet and so shifting the climatic regime.

It is still difficult to predict exactly what effects will occur in particular places, but the overall impacts will be profound, shifting climatic zones, altering rainfall patterns, raising sea-levels and storm frequencies. Up to 40% of all species could be threatened in the process. Furthermore, changes following the predictions are already occurring. These are most marked in the most sensitive regions – towards the poles and in alpine and semi-desert regions – but in the long run it will be the poorest countries that will bear the brunt.