What' s climate change

Climate change represents one of the greatest environmental, social and economic threats facing the planet.

Energy from the sun warms the earth's surface and, as the temperature increases, heat is radiated back into the atmosphere as infra-red energy. Some of the energy is absorbed within the atmosphere by 'greenhouse gases'.

The atmosphere acts in a similar way to the walls of a greenhouse, letting in the visible light and absorbing the outgoing infra-red energy, keeping it warm inside. This natural process is called the "greenhouse effect." Without it, the global average temperature on earth would be -18°C, whereas at the moment it is +15°C.

However, human activities are adding greenhouse gases, particularly carbon dioxide, methane and nitrous oxide, to the atmosphere, which are enhancing the natural greenhouse effect and making the world warmer. This man-made extra warming is called the "enhanced" greenhouse effect. Warmer global temperatures in the atmosphere and oceans result in a climate change phenomena that may affect rainfall patterns, cause storms and sea level rises.

Over the past 100 years the average surface air temperature increased by 0.74 °C globally and by almost 1°C in Europe, which is unusually rapid warming. In fact, the 20th century was the warmest century and the 1990s were the warmest decade in the past 1,000 years. This warming trend is continuing: the 11 hottest years on record have all occurred in the past 12 years.

The Intergovernmental Panel on Climate Change (IPCC), a UN body which brings together hundreds of climate experts from across the world, projects that by 2100 the global average temperature is most likely to increase by a further 1.8°C to 4°C – and in the worst case by up to 6.4°C – unless the world takes action to limit greenhouse gas emissions.

Even the lower end of this range would take the temperature increase since pre-industrial times above 2°C - the threshold beyond which many scientists believe irreversible and possibly catastrophic changes would become more likely.