Download Grade 10 Applied Science – Climate Change

Grade 10 Applied Science – Climate Change
Natural Causes and Human Activity
NATURAL CAUSES
Earth’s climate has been continuously changing. Moreover, these NATURAL changes have been both
long and short term. NOTE: None of these natural causes account for the recent trend in global
warming.
Long-term Changes
 Over hundreds of millions of years, Earth’s land masses have moved and changed position.
Recall the PANGEA from geography.
 The movement has resulted in the formation of mountains. As well, ocean currents and wind
patterns have been altered which, in turn, affect the thermal energy transfer on Earth.
Short-term Changes
 Volcanoes erupt and may release large amounts of dust and gas (e.g., sulphur dioxide) into the
atmosphere. These materials reflect some of the Sun’s energy back into space. This action
cause the Earth’s surface to cool. For example, average global temperatures dropped about 1OC
for about two years after the 1991 eruption of Mount Pinatubo, Philippines, and very cold
temperatures caused crop failures and famine in North America and Europe for two years
following the 1815 eruption of
Tambora, Indonesia (...the
largest volcanic eruption in
recorded history).
 Every three to seven years, El
Niňo events occur in the
Pacific Ocean. During an El
Niňo, the ocean currents
reverse direction. Warm
surface water carrying
moisture usually moves
westward. In an El Niňo, the
warm water goes east. Areas
that are normally dry become
very wet, while normally wet
areas experience desert-like
conditions.
HUMAM SOURCES OF GREENHOUSE GASES
As we know, Greenhouse Gases are a natural part of the Earth’s atmosphere. Yet, we are concerned
about the levels of Greenhouse Gases in the atmosphere. Why?
During the last 200 years, the concentration of Greenhouse Gases in the atmosphere has risen
dramatically. For example, levels of atmospheric carbon dioxide (CO 2) are close to 400 ppm (see Figure
below), a level higher than any time in the last 650,000 years.
Greenhouse Gases produced by human activity are called ANTHROPOGENIC. The main anthropogenic
gases are CO2, methane (CH4) and nitrous oxide (N2O).

The most important
anthropogenic
Greenhouse Gas is
CO2. The primary
source is human
burning of FOSSIL
FUELS (coal, oil and
natural gas formed
from the remains of
organisms with high
carbon content that is
preserved in rocks and
rock materials in the
Earth’s crust). By
burning more and
more fossil fuels,
humans are putting
too much CO2 into the
atmosphere.

The other primary
source of CO2 is
DEFORESTATION. Trees and other plants are CARBON SINKS (i.e., plants remove CO 2 from
the atmosphere and store it temporarily in plant materials). If trees are cut down or burned, the
carbon is put back into the atmosphere. When this occurs, trees are a SOURCE of carbon.

Many human activities release CH4 into the atmosphere. One important source is LANDFILLS.
As garbage decomposes (i.e., breaks down), it releases gas. About 50% is CH 4. The other most
important source is livestock farming. Farm animals, especially cattle, release CH 4 as they digest
food.

Anthropogenic sources of N2O include fertilizers and managing livestock waste.
CARBON FOOTPRINT
It is a term to describe
the total amount of
Greenhouse Gas
emissions produced by
an organization, event,
product or person. The
Greenhouse Gases are
expressed as carbon
dioxide equivalents.
Typically, richer countries
produced the most
Greenhouse Gas
emissions.