Climatic conditions are now monitored right across the world. The widespread deployment of scientific weather instruments over the last century means we can now reliably measure where, and how large, recent changes in climate have been.
There's a wide range of evidence which indicates our climate is warming:
We know from global temperature records that the Earth has warmed by about 0.75°C in the last century. From the 1970s to 1990s warming was faster than over the century as a whole, but the rise has slowed more recently.
Evidence shows rainfall patterns are changing across the globe. Generally, wet places are becoming wetter and dry areas are becoming drier. However, there are also changes between seasons in different regions. For example, rainfall in the UK during summer is decreasing, while in winter it is increasing.
In the UK, the growing season has lengthened due to Spring starting earlier and the delayed onset of autumn/winter. Wildlife experts have noted that many species are changing their behaviour, from butterflies appearing earlier in the year to birds starting to change their migration patterns.
Since 1900, sea-levels have risen by about 10cm around the UK and about 17cm globally, on average. Evidence shows the rate of sea-level rise has increased in recent decades.
Glaciers all over the world are retreating. This has been observed in the Alps, Rockies, Andes, Himalayas, Africa and Alaska.
Arctic sea-ice has been declining since the late 1970s, reducing by about 0.6 million km² per decade - an area about the size of Madagascar.
The Greenland and Antarctic ice-sheets, which between them store the majority of the world's fresh water, have both started to shrink.
Our climate impacts expert Dr Debbie Hemming discusses the evidence of climate change on the Met Office's YouTube page