The first consequences of climate change can already be seen in Europe and around the world. These impacts are predicted to intensify in the coming decades. Temperatures are rising, rainfall patterns are shifting, glaciers are melting, sea levels are getting higher and extreme weather is becoming more common, bringing hazards such as floods and droughts.
These changes pose a serious threat to human lives, to economic development and to the natural world on which much of our prosperity depends.
Our planet's climate has always changed, usually as a result of natural factors like tiny changes in the Earth's path around the sun, volcanic activity, and fluctuations in the climate system. But humans are having an increasing influence on the climate by burning fossil fuels, cutting down rainforests and farming livestock.
Energy from the sun warms the Earth, and our planet radiates some of this heat back out towards space. But certain gases in the atmosphere act like the glass in a greenhouse – they allow the energy to enter the atmosphere, and they also prevent it escaping.
Some greenhouse gases, such as water vapour, are naturally present in the atmosphere. Without them, the Earth's average temperature would be an unbearably cold minus 18ºC instead of the 15ºC it is today.
In the past, climate changes were slow, but now we are in a period of fast warming. Human activities are releasing immense quantities of greenhouse gases into the atmosphere, strengthening the greenhouse effect and warming the climate.
Europe is responding by cutting its greenhouse gas emissions and encouraging other nations to do likewise. But even if we succeed, there will still be some degree of climate change. This is because many greenhouse gases remain in the atmosphere for a long time, and because the oceans work as enormous reservoirs of heat. So we also learn to adapt to some amount of climate change.