Natural Climate ChangesProcesses Resulting in Changes in Climate Trends Over Time

QQ1 – Predict some causes of natural climate change

I. Short Term Natural Climate Changes

A. Changes in climate trends, measured in months to years

1. Seasons

• The shape of the earth causes different areas of Earth to receive different amounts of solar radiation

• This results in variations in daylight, temperature and weather patterns

• When the north pole is pointed toward the sun, the northern hemisphere experiences summer and the southern hemisphere experiences winter (A)

• During spring and fall, neither pole points toward the sun (B)

QQ2–Why does the position of the sun effect seasons & thus climate?

2. Volcanic Activity

• Volcanic dust can remain suspended in the atmosphere for several years

• This blocks incoming solar radiation and lowers global temperatures

1991 eruption of Mt. Pinatubo

1980 eruption of Mt. Saint Helens

QQ3 – What is the effect of reduced solar radiation on the plant?

3. El Nino

• Caused by a warm ocean current that occasionally develops off the west coast of South America, due to a shift in wind patterns

• Negative Effects of El Nino:

Wet, stormy weather occurs in areas that are normally dry

Drought conditions occur in areas that are normally wet

Violent storms brought to California and the Gulf Coast

Extensive property damage and untold human suffering

• Positive Effects of El Nino:

Fewer and less severe hurricanes in the Atlantic ocean regions

Normal: cool dry climate

Pacific Ocean

Cold water is transported north from

Antarctica.

Due to winds, Waters are warm

in W. Pacific

Normal Conditions El Nino Conditions

Pacific Ocean

The cool dry climate

becomes warm and wet!

Westerly trade winds weaken

and warm water flows east

Antarctica

II. Long Term Natural Climate Changes

A. Changes in climate trends, measured over tens of thousands to hundreds of thousands of years

1. Ice Ages

• Glaciers have alternatively advanced and retreated over the past 2 million years

• Ice Ages are periods of extensive glacial coverage

• Global temperatures drop 5 degrees Celsius on average

• Most recent Ice Age ended 10,000 years ago

2. Earth’s Orbit

• Every 100,000 years, the shape of Earth’s orbit changes, becoming more elliptical, then more circular

• When the orbit elongates, earth passes closer to the sun and temperatures become warmer than normal

• When the orbit is more circular, temperatures dip below average

3. Earth’s Axis

• The angle of tilt varies from 22.1º to 24.5º every 41,000 years

• Changes in angle cause seasons to become more severe

• A decreased tilt might cause winters to be warmer than normal and summers to be cooler than normal

• Changes in tilt may be responsible for Ice Ages

4. Earth’s Wobble

• Over a period of 26,000 years, Earth wobbles as it spins on its axis

• Currently the axis points toward the North Star (Polaris) and winter occurs in the Northern Hemisphere when Earth is closest to the sun

• When the axis tilts toward Vega, winter will occur in the northern hemisphere when Earth is farthest from the sun

This will cause warmer summers and colder winters than those we now experience

QQ4 – What causes Earth’s orbit, tilt, and wobble to change?