ATMO 11/18 - Climate Change

Proxy Records - Inferred records of past climate that are not based on
direct measurement. Information can be obtained about past temperature
and precipitation patterns as well as past concentrations of some
greenhouse gases. Climate reconstruction based on proxy records are by
no means certain and are only estimates.

Pleistocene Epic:
- Period from ~2 million years ago to ~15k years ago
- Alternating glacial (ice ages, glaciers advancing) and interglacial
(glaciers retreat) periods
- At least 20 glacial/interglacial cycles

Many geoscientists believe the increase in temperature led to increase
in greenhouse gases (warmer water cannot dissolve as much CO2 or
Methane, therefore it is released into the atmosphere)

We are currently in a warming interglacial period

Is our planet fragile or robust?
- Is the climate system and life on Earth fragile or robust? Easy to
change or hard to change?
- Is adding CO2 poisoning our environment?
- Some extinctions have been caused by slight changes in local environments
- The entire biosphere can be considered robust, but individual
species the Earth can be considered fragile

The climate of the Holocene:
- Holocene Epoch - the present interglacial period which began after
the peak of the last true ice age ~15k years ago

- Younger Dryas - 500-1,000 years of where the temperature was
relatively cold and rapidly changed 12k-11.5k years ago. Dropped 2C in
under 50 years (very rapid change), then after 1,000 years
temperatures increased by 3C in about 50 years. Major natural
fluctuations have occurred during the Holocene. This shows how
sensitive the climate can be.

- Holocene Maximum - 14k-10k years ago, Humans did much better during
this warm period often labeled a maximum or optimum.
- Medieval Warm Period - 1100-1300AD where temperatures were 1C warmer than 1900
- Little Ice Age - 1550-1850AD where temperatures were 1C less than 1900

- In Europe during these times there were major changes in societies
- Medieval period had grapes grown in England and Wheat grown in
Norway (64 degrees north latitude)
- Little Ice Age period had significantly less agricultural productivity

Periods to remember:
- 5000-3000 BC, Holocene Optimum - warmest temperatures of the entire
Holocene period, warmer than today
- 600-300 BC, Pre-Roman Cool Period
- 200BC-400AD, Roman Warm Period
- 600-900 AD, Dark Ages Cool Period
- 1100-1300 AD, Medieval Warm Period
- 1550-1850 AD, Little Ice Age
- 1900-Present, Modern Warming Period