Transcript Guided Notes on Climatic Changes

Guided Notes on Climatic
Changes
Chapter 14, Section 3
1. During the average human lifetime,
climates do not appear to change
significantly. However, climates always
have been in a constant state of change.
2. Glaciers have alternatively advanced and
retreated over the past 2 million years.
Periods of extensive glacial coverage are
called ice ages, during which average global
temperatures decrease by 5 degrees Celcius.
Ice ages alternate with warm periods called
interglacial intervals.
3. Seasons are short-term periods of climatic
change caused by regular variations in
daylight, temperature, and weather patterns.
These variations are the result of changes in
the amount of solar radiation that an area
receives.
Define and describe the El Niño
effect
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El Niño is a warm ocean current that
occasionally develops off the western coast of
South America.
It creates a warmer and wetter climate along
the northwestern coast of South America and
brings violent storms to California and the
Gulf Coast.
5. The one positive effect of an El Niño is that
the strong upper winds keep tropical
disturbances from increasing to hurricanes in
the Atlantic Ocean. This results in fewer
hurricanes for the duration of the El Niño.
6. Studies of tree rings, ice-core samples,
fossils, and radiocarbon samples
provide evidence of past climatic
changes.
7. Evidence of a possible link between solar
activity and the Earth’s climate was proposed
by E.W. Maunder in 1893. He correlated a
period of very low sunspot activity with an
unusually cold climatic episode called the
“Little Ice Age”.
8. Studies indicate that increased solar
activity coincides with warmer-thannormal climates, while periods of low
solar activity coincide with cold climatic
conditions.
9. The shape of Earth’s elliptical orbit appears to
change over a 100,000 year cycle. When the
orbit elongates, Earth passes closer to the
Sun, and temperatures become warmer than
normal. When the orbit is more circular,
Earth is farther from the Sun and
temperatures dip below average.
10. The angle of tilt of the Earth’s axis
varies from a minimum of 22.1 degrees
to a maximum of 24.5 degrees every
41,000 years. Scientists believe that
these changes cause seasons to become
more severe.
11. Over a period of about 26,000 years,
Earth wobbles as it spins on its axis.
Currently the axis points toward the
North Star, Polaris. By the year 14,000,
the axis will point toward Vega, another
star.
12. When the axis tilts toward Vega, winter will
occur in the northern hemisphere when Earth
is farthest from the Sun and summer will
occur when Earth is closest to the Sun. This
will cause warmer summers and colder
winters to occur.
13. Climate changes can be triggered by the
immense quantities of dust released by
volcanic eruptions. This dust blocks
incoming solar radiation and thus
lowers global temperatures.