Lecture 10 CM

Question 1

Over the last 2 million years

Answer 1

known as the Pleistocene period)

Question 2

Global climate has been

Answer 2

the global climate has on average been much colder than at present, with frequent and prolonged ice ages

Question 3

The last ice age ended 20,000 years bp, marking the beginning of the

Answer 3

Holocene

Question 4

This plot represents inferred climate history of North Atlantic over last 100,000 years:

Answer 4

Relative O2 isotope concentrations in fossilized ice from the Greenland Ice Core Project (GRIP) reveal dramatic fluctuations in the Earth’s atmospheric temperature.

Question 5

Since the end of the Pleistocene the global climate has experienced a slow but incremental warming due to:

Answer 5

(i) A background fluctuation in the elliptical orbit of the the Earth around the Sun (Milankovitch, proposed 1930s)
(ii) Gradual changes in the Earth’s axial tilt
(iii) Background changes in atmospheric greenhouse gas concentrations (associated with vegetation and ocean temperature)
(iv) The knock-on effect of the changing configuration of the continents (which effect ocean currents like the gulf stream)

Question 6

At the height of the last Pleistocene ice age 20,000 years bp, i

Answer 6

ice sheets covered large areas of the Northern Hemisphere – very different from today.

Question 7

Biome distributions were also very different,

Answer 7

with a contraction of the extent and latitude of all biomes towards the equator.

Question 8

The rate of increase in greenhouse gases that accompanied the end of the ice-age (and a global rise in temperature of 4.5oC)

Answer 8

was 10 times slower than current anthropogenic increases.