Download Long and Short-term Changes in Climate

SNC2D – Earth and Space Science: Climate Change
Long-term and Short-term Changes in Climate
(pp. 348-352)
Terms and Concepts: plate tectonics, continental drift, ice age, interglacial period, Milankovitch Cycles
Long-term Changes due to Continental Drift
Plate Tectonics (Continental Drift):
The theory that:

the earth’s continents have moved slowly over the surface of the globe for hundreds of millions of
years;

there used to be one supercontinent named Pangaea.
Effects on climate when continents move:

ocean and wind patterns change (affects heat transfer)

distribution of land mass changes (e.g. large land masses - cold winters, warm summers)

uplifts new mountain ranges (affects local and regional climate)
Long-term cycles in climate
It is believed that the earth’s climate cycles between ices ages and interglacial periods.
Ice age:
A period of time when the earth is colder and much of the planet is covered in ice.
Interglacial period:
A time between ice ages when the Earth warms up
About 20,000 years ago, the earth experienced its last ice age. The average temperature was 10C lower
than today. Ice sheets about 3 km thick covered much of Canada. Today, we are in an interglacial
(warming) period.
Frequency of warm interglacial periods: about every 100,000 years.
SNC2D – Earth and Space Science: Climate Change
A. M. Hogg, Glacial cycles and carbon dioxide, a conceptual model, Geophysical Research Letters, Vol. 35,
doi:10.1029/2007GL032071, 5 pp, 2008
Why do Interglacial and Ice Ages happen?
Serbian engineer and astronomer Milutin
Milankovitch theorized that the ice age
cycles occur because the earth’s orbit
around the sun changes in 3 main ways:
● Eccentricity: shape of orbit (more or less
elliptical)
Cycle of 100,000 years
● Tilt (affects the seasons), changes from
22.1° to 24.5°
Cycle of 41,000 years
● Precession: wobbles on its axis
Cycle of 26,000 years
These changes add up to the regular cycles of ice ages and interglacial periods
1. How might the shape of the earth’s orbit affect temperatures on earth? When might ice ages be more likely:
when the orbit is more elliptical or less elliptical?
2. How might the tilt of the earth affect the parts of the earth that receive the direct rays of the sun? When might
polar ice be more likely to grow (and ice ages to occur): when the earth is more tilted or less tilted?
3. How might precession of the earth affect the growth of polar ice (and therefore the occurrence of ice ages):
when the precession has tilted the earth towards the sun or away from the sun?
SNC2D – Earth and Space Science: Climate Change
Short Term Variations in Climate
1. Volcanic Eruptions

Spew rocks, dust and gases into the atmosphere

Sulfur dioxide (SO2) reflects the sun and earth temporarily cools down.
Case Study: The eruption of Mt. Pinatubo in the Philippines in 1991 contributed to a small decrease in Northern
Hemisphere temperatures for a few years.
2. Small changes in the sun’s radiation

The amount of solar radiation changes in small amounts over about 11 year cycles. We are currently
in a solar minimum.
3. Air and Ocean currents
Some changes in air and ocean currents occur regularly. A dramatic change takes place in the Pacific
Ocean every three to seven years.
El Nino: periodic shift in Pacific winds and ocean currents; west coast of South America receives
warmer, wetter weather