Climate change refers to long-term shifts of the Earth’s atmospheric conditions, such as temperature, snow and rainfall patterns, and extreme weather events (like floods or storms). It is caused by rising levels of greenhouse gases in the atmosphere, mostly from human activities – burning fossil fuels like coal, oil and natural gas, agriculture and deforestation.

These gases act like an insulating blanket, trapping some of the sun’s energy and warming the air and Earth’s surface. But as CO2 concentrations increase, the blanket gets thicker and warmer, and the rate of climate change accelerates. This is called a feedback loop.

Observations of global average temperatures, melting ice sheets and changing sea levels show that the world is warming at a rate unprecedented in millennia. Climate change is occurring faster than predicted by scientists and it threatens the health, wellbeing and livelihoods of billions of people.

Temperature, water vapour, the extent of polar ice sheets and concentrations of long-lived greenhouse gases such as carbon dioxide are closely linked. As one changes, the others react through a range of processes known as ‘feedbacks’, amplifying or dampening the original disturbance. This makes it difficult to predict the exact effects of climate change. It is also impossible to know when the system might reach critical thresholds, which could have catastrophic consequences for life on Earth. Nevertheless, the main cause of climate change is clear – fossil fuels (coal, oil and gas), with transport (cars, buses and trains), farming and land clearing contributing less.