Glacial stages are linked to regular patterns in the movements of the Earth.
The ice would start to return in around 1,500 years.
So the current rise in temperatures is not part of a natural cycle.
The natural cooling trend has been reversed.
This temperature rise is the effect of extra carbon dioxide.
The carbon dioxide has been produced mainly by burning fossil fuels.
(In the graph, Law Dome is a site in Antarctica where ice cores have been drilled to discover the ancient CO2 values - Mauna Loa is a site in Hawaii where the CO2 value has been measured in the air since the 1950s)