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Discussion 4/24
Climate patterns & climate change
THE CHANGING CLIMATE
• Climate involves more than just the atmosphere.
• Climate may be broadly defined as the long-term
behavior of global environmental system
• “To understand fully and to predict changes in the
atmospheric component of the climate system. one
must first understand the sun, oceans, ice sheets,
solid earth, and all forms of life"
• Thus we talk about a climate system consisting of
the atmosphere, hydrosphere, solid earth,
biosphere and cryosphere.
• Climate system involves the exchange of energy
and moisture among these components
Fig. 14-3, p. 414
World map of the Kopper climate classification scheme
Fig. 14-2, p. 413
Fig. 14-3, p. 414
Highland climate (H)
DETECTING CLIMATE CHANGE
• DIFFICULT TO DETECT CLIMATE CHANGE EXCEPT
OVER LONG PERIODS OF TIME.
• INSTRUMENTAL RECORDS GO BACK ONLY A
COUPLE OF CENTURIES. THE FURTHER BACK,
THE LESS RELIABLE ARE THE DATA.
• SCIENTISTS MUST DECIPHER CHANGES FROM
INDIRECT EVIDENCE
• HISTORICAL DOCUMENTS
• TREE RINGS
• POLLEN RECORDS
• GLACIAL ICE – AIR BUBBLES AND DUST
• SEA-FLOOR, MATINE SEDIMENTS. OXYGEN
ISOTOPE RATIOS IN FOSSIL SHELLS
• FOSSIL RECORDS
CLIMATE CLUES
POLLEN RECORDS
• Pollen degrades slowly and each species can
be identified by the shape of its pollen
• Radioactive carbon dating gives the age of the
pollen.
• As the climate changes, different types of
species become dominant
• Hence the pollen record can be used to
identify the type of climate that existed
POLLEN RECORDS
ICE SHEETS
• Each year snow falls on the ice sheets and
glaciers. As it accumulates it compresses and traps
air bubbles.
• These bubbles of air trapped in ice can be
analyzed to determine atmospheric composition.
• Glaciers that exist today can hold bubbles that are
tens or hundreds of thousand of years old.
• Dust in the ice sheets can be caused by climatechanging volcanoes, or dry windy conditions that
lead to soil erosion.
• Find that the colder periods of the Earth history
(20000, 60,000 and 100,000 years ago) are usually
much dustier
Concentration of Carbon Dioxide and Methane
determined from air bubbles in ice cores.
Fig. 14-18, p. 426
MARINE SEDIMENTS/FOSSIL RECORDS
• Foraminifera are micro-organisms that live in the sea
and have a calcium carbonate shell. CaCO3
• As the foraminifera die they sink to the ocean floor
to form chalk deposits.
• Among these chalk deposits one also find fossil
shells.
• Oxygen has two isotopes which have an atomic mass
of 16 and 18
• The ratio of these two isotopes in the shells and
foraminifera is a function of the sea temperature
• Fossils reveal ancient animal and plant life that can
be used to infer climate characteristics of the past
NATURAL CAUSES OF CLIMATE CHANGE
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UNRELATED TO HUMAN ACTIVITY.
VOLCANIC ACTIVITY
ASTEROID IMPACTS
SOLAR VARIABILITY
VARIATIONS IN THE EARTH'S ORBIT
PLATE TECTONICS
CHANGES IN THE OCEAN CIRCULATION PATTERNS