The greenhouse effect is a natural phenomenon that keeps the planet approximately 30°C warmer than it would be otherwise. Without the greenhouse effect human life would simply not exist!

The greenhouse effect is caused by carbon dioxide and other greenhouse gases (GHGs) that allow heat from the sun into the atmosphere then trap it like a blanket. While the greenhouse effect is natural, human civilisation (primarily developed nations) has greatly increased its intensity in the last 200 years. Rapid industrialisation has not only increased the concentration of GHGs in the atmosphere, it has also reduced the planet’s capacity to absorb GHGs by land-use change and deforestation (forests act as the lungs of the earth and breath in carbon dioxide). The problem is complex but the basic equation is simple – the more GHGs in the atmosphere, the hotter it becomes. An increased mean global temperature affects our earth system in a variety of interrelated ways and results in what is commonly referred to as climate change.

The level of GHGs emitted into the atmosphere has risen dramatically since 1750 and is now higher than at any other time in the past 650,000 years. The global mean temperature has risen by 0.7°C since 1900. Of the 928 papers referring to ‘global climate change’ published in science journals between 1993 and 2003, not one of them disagreed with the consensus position that the anthropogenic emission of carbon dioxide is leading to global warming. Uncertainty regarding climate change now only concerns the impacts – what, when and how much?

Climate change brings other complications. There are predicted time lags in the climate system that means significant delays between the cause and effect of our actions. Measurements are also subject to temporal and spatial variability which makes the rate and extent of change difficult to predict. On top of this, ‘positive feedbacks’ in the climate system mean that some of the effects of climate change actually accelerate the change process. An example of this is how permafrost melted by global warming releases methane into the atmosphere and in turn causes climate change. Ultimately, there may be tipping points in the climate system where the planet’s environment experiences abrupt and potentially irreversible changes.

Additional Reading:

Global Climate Change: An Introduction-Sudip Mitra

The Stern Review On The Economics Of Climate Change – Executive Summary

Climate Change Glossary