Source 1 - The Glacier d’Argentière in France. In areas of high altitude each year’s snowfall builds up as distinct layers.

Source 2 - When enough ice forms it slowly starts to slide downhill and becomes a glacier.

Source 3 - El Capitan in Yosemite National Park in America. The U-shaped valley here is almost vertical so the sheer face makes it a tremendous challenge for climbers.

Source 4 – The New York skyline today. The image shows the different types of the rock on which the city has been built.

Source 5 - The Albedo effect. Ice is light so reflects heat energy from the sun, whereas the land and sea are dark so absorb heat energy.

Source 6 – The area covered by ice during the last ice age.

Source 7 –Simplified image to show the changes brought about by natural selection to the human species .

Source 8 – Then and now… This image has been taken in the same location and shows the extent of glacial retreat.

Source 10 – Moulin on the massive Jakobshavn glacier in Greenland. Over the last 10 years the glacier has speeded up. It’s now moving at 40m per day and this has made it much thinner.

Source 9 – Two satellite images showing the recent changes to the size of the summer melt zone in Greenland.

Source 11 – Two satellite images of London showing the likely effects on London should all arctic sea ice melt.

Source 12 –Line graphs showing the global carbon dioxide concentration in the atmosphere and the temperature change from the present day over the last 400,000 years.