CLIMATIC FLUCTUATIONS

“Ice house” or “green house”?

During the last 2000 million years the Earth's climate has alternated between periods of cold "ice house" conditions, when conditions were like today's world, and periods when there were steaming "green house" conditions.

Follow the link below to see a chart showing how global climate has changed through time.

http://www.scotese.com/climate.htm

Ice Ages have occurred throughout geological time. How do we know?

GEOLOGICAL PERIOD / EVIDENCE
Precambrian / Tillite (lithified boulder clay) found in rocks in Scotland
End Ordovician / Regressive sediments show lowering of sea level, e.g. at Coniston in the Lake District
Carboniferous / Eustatic sea level changes
Pleistocene

Generally it seems that onset of glaciation is slow but melting as the climate warms up is a rapid process.