Determining Past Climates Sediment cores Ice cores Oxygen isotope ratios Dendrochronology (tree rings )

Temperature reconstruction Medieval warm periodLittle Ice Age

Vostok Station, Antarctica

The Earth climate during the last 2 million years has been dominated by shifts between colder periods, known as Ice ages( or Glacial period) and warmer periods, known as interglacial period. Ice Ages have tended to last for up to 100,000 years. Interglacial periods have usually been much shorter in duration, at around 10,000 years in length. Glacial & Interglacial Period

Last glacial period Earth during the last Ice Age (at about the last glacial maximum, 16,000 B.C.).

CO 2 Versus Temperature Before Present (BP) years was used as the arbitrary origin of the age scale

The Younger Dryas An event that occurred about 12,800 years before present (BP), termed the Younger Dryas (YD), is the example of abrupt climate change.

Younger Dryas Period

Evidence -Younger Dryas Period The evidence comes from the reappearance of the Dryas flower in the Alps, which flourishes in glacial climates

Thermohaline Circulation – Global Conveyor belt Thermohaline circulation is a very slow and extremely deep movement of water in the oceans around the world. It links major surface and deep water currents in the Atlantic, Indian, Pacific, and Southern Ocean.

Thermohaline circulation

Atlantic Conveyor Shutdown

What turns ice ages on and off?" The amount of sunlight receives by the Earth changes, due to; Orbit of Earth Tilt of Earth Earth’s wobble

Shape of the Earth’s Orbit

Earth’s Tilt.

Earth’s Wobble