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Natural Variability of Climate (Ice Ages, Warm Period, Extremes)


3.1.1.d         Natural Variability of Climate (Ice Ages, Warm Period, Extremes)

Paleoclimate Fluctuations

Earth’s climate has undergone dramatic swings.

Paleoclimatology means the study of past climates. There have been many periods of climate change. These periods can be identified by their durations. Long cool periods that last from tens to hundreds of millions of years are called ice ages. During this time span, glaciers advance and retreat.

Through most of its history the Earth has been considerably warmer that it is today.

ACTIVITY 1 Questions

  1. What span of time does the graph encompass?
  2. How many glaciations were in the Precambrian?
  3. Identify the dates of the ice ages and use the Timescale to:– name the eras and periods in which they occurred; — identify other significant events (land, oceans, vegetation, animals).



Some climatic fluctuations in the Cenezoic Era:

  • The Little Ice Age: a cool period from 1400 to 1860 A.D characterized by harsh winters, shorter growing seasons, and a drier climate. Has been blamed for many catastrophes including crop failures like the Irish Potato Famine.
  • Medieval Warm Period: a warm spell from approximately A.D. 1000 to A.D. 1350 that existed just prior to the Little Ice Age.
  • Holocene Maximum: highest temperature in the Cenozoic
  • Younger Dryas: a cold spell 21,000 years ago named after an arctic-alpine plant “Dryas” that populated Europe during the cold conditions.
  • Kargian Warm Period – around 42,000 to 25,000 years ago.

The Oligocene (mid Tertiary) marked the transition from a hot to a cold world coinciding with the transition from circumequatorial to circumpolar ocean circulation.

The world also changed from submerged to emergent continents that drifted to high latitude creating greater seasonal changes. Climates at high latitude became more severe.

ACTIVITY 2 Questions

  1. What span of time was earth’s last full climate cycle?
  2. What are the highest and lowest mean global temperatures in that cycle?
  3. What does the dotted line on the right of the graph mean?
  4. Use the Timescale to identify other significant events (land, oceans, vegetation, animals)