Climate change: How do we know it is happening and caused by humans?
Scientists and politicians say we are facing a planetary crisis because of climate change.
Greenhouse gases - which trap the Sun's heat - are the crucial link between temperature rise and human activities.
But what's the evidence for global warming and how do we know it's being caused by humans?
How do we know the world is getting warmer?
Our planet has been warming rapidly since the dawn of the Industrial Revolution. The average temperature at the Earth's surface has risen about 1.1C since 1850. Furthermore, each of the last four decades has been warmer than any that preceded it, since the middle of the 19th Century. These conclusions come from analyses of millions of measurements gathered in different parts of the world. The temperature readings are collected by weather stations on land, on ships and by satellites. Multiple independent teams of scientists have reached the same result - a spike in temperatures coinciding with the onset of the industrial era. [continue]