Unit 4 Part 1.2 Climate Ch 21.3 Climate Changes

Describe the natural processes that can cause climate changes

1.  Plate tectonics

Geographic changes in the Earth’s land and oceans due to plate tectonics cause changes in climate over very long time scales.

Large supercontinents such as Pangaea developed monsoon climates

Most important, mountain building cooled the global climate.  When India collided with Asia, the Himalayan Mountains formed.  As the mountain began to erode, sediments washed down into the ocean.  The sediments combine with carbon dioxide to form carbonate rocks like limestone.  Before the Himalayas, there was three times more carbon dioxide than is on Earth today.

2.  Earth’s orbital motion
Changes in the shape of Earth’s orbit and the tilt of the Earth’s axis of rotation affect global climates over intermediate time scales.

Eccentricity

Precession

Tilt

Use this link for eccentricity

Use this link for Earth’s tilt

Use this link to see three ways that Earth’s orbit changes over time

Use this link to see animations of the three ways that Earth’s orbit changes over time

3.  Ocean circulation
These changes in ocean circulation also can result in short-term climate fluctuations

Example El Nino is a change in ocean circulation that causes parts of the eastern tropical Pacific Ocean to become warmer than usual.
4.  Solar activity
Over short time scales, fluctuations in the amount of solar radiation can change global climates

An increase in sunspots appears to correspond with warm periods in Europe and North America.

Fewer sunspots seem to be correlated with cooler periods.  The “Little Ice Age” in Europe during the 1600’s occurred when there were very few sunspots.

5.  Volcanic eruptions
Volcanic ash, dust, and sulfur-based aerosols in the air increase the amount of solar radiation that is reflected back into space.  This causes Earth’s lower atmosphere to cool.

What is the greenhouse Effect?

The natural warming of both Earth’s lower atmosphere and Earth’s surface

What is global warming?

As a result of increases in carbon dioxide levels, as well as other greenhouse gases, global temperatures have increased.  This increase is global warming.

What are some consequences of global warming?

Warmer temperatures increase evaporation rates.  Increased water vapor in air will magnify affect of greenhouse gases.

Temperature increase will cause sea ice to melt.  Ice reflects more of the sun’s radiation than water does.  This will substantially increase the amount of solar energy absorbed.

Melting of sea ice and ice sheets will cause a global rise in sea level causing shoreline erosion and coastal flooding.

Weather patterns may change.  These would include more severe droughts and heat waves in some areas.

 Use this link to see the effect of climate change around the world.