Download class viii science theme 2

THEME: 2
OTBA Paper – Session 2016-17
Class VIII
Subject: SCIENCE
What is Global Warming and Climate Change?
Global warming and climate change refer to an increase in
average global temperatures. Natural events and human activities
are believed to be contributing to an increase in average global
temperatures. This is caused primarily by increases
in greenhouse gases such as Carbon Dioxide (CO2).
The main indicators of Climate Change are.
What is the Greenhouse Effect?
The term greenhouse is used in conjunction with the phenomenon
known as the greenhouse effect.

Energy from the sun drives the earth’s weather and climate, and heats
the earth’s surface;

In turn, the earth radiates energy back into space;

Some atmospheric gases (water vapor, carbon dioxide, and other
gases) trap some of the outgoing energy, retaining heat somewhat like
the glass panels of a greenhouse;

These gases are therefore known as greenhouse gases;

The greenhouse effect is the rise in temperature on Earth as certain
gases in the atmosphere trap energy.
Six main greenhouse gases are carbon dioxide (CO2), methane (CH4) (which is 20
times as potent a greenhouse gas as carbon dioxide) and nitrous oxide (N2O), plus
three fluorinated industrial gases: hydrofluorocarbons (HFCs), perfluorocarbons
(PFCs) and Sulphur hexafluoride (SF6). Water vapor is also considered a
greenhouse gas.
Source: John
As John Cook, creator of the graphic above says (see above link), Just as it
takes time for a cup of coffee to release heat into the air, so to it takes time
for the ocean to release its heat into the atmosphere..
Indeed, as this chart also shows, the warming in the oceans has been occurring for
quite some time:
Arctic has been heating up, and studies show that is happening at two to three
times the global average. This rising temperature in the Arctic has served to reduce
the region’s floating ice layer by more than 20%. And as you would expect, when
the reflective ice and snow layer is stripped away, it leaves a dark blue sea.
Now, what does the effect of the dark blue sea being exposed have on the Arctic
area? Well, the ice and snow layer reflects the majority of the sun’s rays
harmlessly back into space. But the dark blue of the exposed sea absorbs the rays,
aiding the heating process.
What are the impacts of Global
Warming?
For decades, greenhouse gases, such as carbon dioxide have
been increasing in the atmosphere. But why does that matter?
Won’t warmer weather be nicer for everyone?
Rapid changes in global temperature
It is the rapid pace at which the temperature will rise that will result in many
negative impacts to humans and the environment and this why there is such a
world-wide concern.
Extreme Weather Patterns
Most scientists believe that the warming of the climate will lead to more extreme weather
patterns such as:



More hurricanes and drought;
Longer spells of dry heat or intense rain (depending on where you are in the world);
In South Asia, the Himalayan glaciers could retreat causing water scarcity in the long run.
Ecosystem Impacts






Rapid global heating according to a US National Academy of Science warning;
Dramatic increase in greenhouse gas emissions;
Ozone loss aggravated by global warming;
Ozone loss likely to aggravate global warming;
Warming of the oceans leads to increased greenhouse gasses;
While effective measures can decrease global warming and other problems the World
community has repeatedly failed to establish cooperation.
Rising Sea Levels
Water expands when heated, and sea levels are expected to rise due to climate change. Rising sea
levels will also result as the polar caps begin to melt.