What is Global Warming?

Global warming is a term used to describe the increase in temperature of the Earth’s atmosphere and oceans. Scientists from the Intergovernmental Panel on Climate Change (IPCC) estimate that the global temperature increased with 0,6°C ± 0,2°C since the end of the 19^th century and that most of the increase over the last 50 years is caused by human activities.

However, some skeptics claim that the whole global warming is a natural process that has little to do with the human greenhouse gas emission. At this moment we are in the 'Holocene' of the geological timescale, or the last 'interglacial' (a period of 10.000 year between two ice ages). Several scientists believe that we are to start a new ice age and that the climate changes are thus a natural phenomena. However, the rate at which the climate is changing is far beyond natural.

The causes:

The temperature of the Earth is defined by a balance of several factors; in general, the natural increase in the Earth’s temperature is caused by

• Solar radiation
• Heat of the Earth itself

Decrease of the Earth’s temperature is caused by

• Photosynthesis
• Infrared radiation from the Earth

The whole is kept in balance by the natural regulation of the infrared radiation from the Earth. However, gasses in the atmosphere work as a ‘blanket’ keeping the Earth’s heat in the atmosphere. Without this natural “greenhouse effect”, the global temperature would be at least 30°C lower and the Earth would be inhabitable.

This greenhouse effect however, is being increased by human activity, due to an increase of greenhouse gases in the atmosphere (like e.g. carbon dioxide (CO₂) and methane (CH₄)). These gases cause a decrease in heat-loss by infrared radiation from the Earth’s surface and thus an increase in the Earth’s temperature.

The atmospheric concentrations of CO₂ and CH₄ have increased by 31% and 149% respectively above pre-industrial levels since 1750. This is considerably higher than at any time during the last 420.000 years! From less direct geological evidence it is believed that CO₂ values this high were last attained 40 million years ago! About 3/4 of the anthropogenic emissions of CO₂ to the atmosphere during the past 20 years is due to fossil fuel burning. The rest is predominantly due to land-use change, automobile exhaust and especially deforestation.

However, it is very complex to predict exactly what effects  the greenhouse gases will have on the global temperature in the future. Some estimates predict that the temperature will increase with 1,4°C to 5,8°C by 2100 with devastating effects on the whole planet, including the human population.

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