So How is this linked to last lesson? HW Answer The Thames regularly froze in the past! So How is this linked to last lesson? The Thames no longer freezes like this so indicates we are in a warmer period! Feb 1814 was one winter famous for its frost fares!

Global Temperature Change Key Question: What other evidence do geologists have for temperature change? Key Words: Ice Cores Tree Rings (Dendrochronology) Pollen Analysis Deep Sea Sediments

Other evidence for temperature change LISTEN TO THE FOLLOWING OTHER EVIDENCE CAREFULLY…….. You will need it in a later task

Ice Core Analysis Recent decades coring of polar glaciers/ice sheets. Cores  represent annual increments of frozen precipitation. Drilling of 2 cores to bedrock in the thickest Part of the Greenland ice sheet (>3km thick) by: American Greenland Ice Sheet Project (GISP 2) European Greenland Ice-Core Project (GRIP) Provided evidence of scale, speed and how often the temperature changed

Ice Core Analysis Annual Ice Increments (equivalent to calendar years, clarity diminishes with depth) Air Bubbles: Contain CO2 and Methane and stable isotopes Winter layers – light Summer Layers - dark Biological Material: Microbe/fungal spores/pollen Dust Content Evidence of aeolian activity, Volcanic Dust Chemical Content Provides record of past volcanic activity Type of Oxygen either heavy or isotopically lighter – 18O:16O Provides evidence of past surface ocean temperature.

Summer Layers Winter Layers

Pollen Analysis Most versatile technique When plants releases spores, some may become preserved in sediments Plant species require particular climatic requirements which influence their geographic location. Pollen can therefore reveal information about vegetation changes through time and indirectly climate.

Dendrochronology Trees growing N/S of equator grow 2 bands Spring Bands – Wider (rapid growth) Autumn/Winter – Narrower (slower growth) Wider rings = more rapid growth indicating warmer conditions Change in the width most important from year to year as trees often grow wider rings in early years.

Winter Summer

Deep Sea Sediments Provide a complete record of micro-fossil evidence diatoms and forams The type/distribution of the microfossils present indicate the climatic conditions that prevailed during their existence.

Now have a go yourselves at completing the evidence for temperature change worksheet