Section 4 Earth’s Changing Climate

Seasonal Changes As the Earth completes one revolution around the Sun, the Earth will experience all four seasons. Summer when the hemisphere is tilted toward Sun Winter when the hemisphere is tilted away from Sun

Long-term Changes Glaciations (Ice ages), represent long-term climatic changes. Peak of last ice age was 18,000 – 22,000 yrs ago. Global climate was 6°C cooler. World Climate reached current pattern 3,000 yrs ago.

Cause of Climate Change Earth’s orbit produces changes that result in the rhythmic cycles of glaciation. Tilt of Earth’s axis varies causing changes in climate. The amount of solar radiation can also have a huge impact on the climate. Sunspots can cause the earth’s climate to fluctuate.

Human Factor Humans modify surface heating, the water cycle and carbon cycle. Also increase atmospheric dust and pollution. Deforestation causes less carbon being absorbed from the atmosphere. Increases green house gases. The increase in temperature of water also decreases its ability to absorb carbon. Human activity have also increased Methane and Nitrous oxide; which increase temp.

Human Factor Human activity increases global warming By how much is up for debate. Earth has had an unusual period of stable climate for the last couple thousand years. Earth goes through natural periods of warming and cooling. Earth is in a period of warming; which is typically followed by a period of cooling.

Ozone Hole Some chemical compounds are known to destroy the ozone (O3). Chlorofluorocarbons (CFC’s) are known to destroy O3. Large hole over Antarctica is getting bigger since it was discovered in 1970’s After scientist discovered Ozone hole a decrease in the use of CFC’s was agreed upon by the world.

El Niño and La Niña El Niño- is the warming of water in western Pacific that can dramatically change the climate of western coasts of US and South America. La Niña- is the cooling of the Pacific which causes droughts in southern US and excess rain in the northwestern US. Both are effects caused by the trade winds near the equator. La Niña is caused by unusually strong trade winds.