2. • What is global warming?
• Observed temperature changes.
• Causes of global warming.
• What is greenhouse effect?
• Greenhouse gases.
• Role in climate change.
3. • Global Warming is the increase of Earth's average
surface temperature due to effect of greenhouse gases,
such as carbon dioxide emissions from burning fossil
fuels or from deforestation, which trap heat that would
otherwise escape from Earth.
4. • The increase in ocean heat content is much larger than
any other store of energy in the Earth’s heat balance over
the two periods 1961 to 2003 and 1993 to 2003, and
accounts for more than 90% of the possible increase in
heat content of the Earth system during these periods.
• Two millennia of mean surface temperatures according to
different reconstructions from climate proxies, each
smoothed on a decadal scale, with the instrumental
temperature record overlaid in black.
5. • Global warming is primarily a problem of too much
carbon dioxide (CO2) in the atmosphere—which acts as
a blanket, trapping heat and warming the planet.
• As we burn fossil fuels like coal, oil and natural gas for
energy or cut down and burn forests to create pastures
and plantations, carbon accumulates and overloads our
atmosphere.
• Certain waste management and agricultural practices
aggravate the problem by releasing other potent global
warming gases, such as methane and nitrous oxide.
• See the pie chart for a breakdown of heat-trapping
global warming emissions by economic sector.
6. • The greenhouse effect is a process by which thermal
radiation from a planetary surface is absorbed by
atmospheric greenhouse gases, and is re-radiated in all
directions. Since part of this re-radiation is back towards
the surface and the lower atmosphere, it results in an
elevation of the average surface temperature above what
it would be in the absence of the gases.
7. • A greenhouse gas (sometimes abbreviated GHG) is a
gas in an atmosphere that absorbs and emits radiation
within the thermal infrared range. This process is the
fundamental cause of the greenhouse effect. The primary
greenhouse gases in the Earth's atmosphere are water
vapor, carbon dioxide, methane, nitrous oxide,
and ozone.
• By their percentage contribution to the greenhouse effect
on Earth the four major gases are
• water vapor, 36–70%
• carbon dioxide, 9–26%
• methane, 4–9%
• ozone, 3–7%
8. • Strengthening of the greenhouse effect through human
activities is known as the enhanced (or anthropogenic)
greenhouse effect. This increase irradiative forcing from
human activity is attributable mainly to increased atmospheric
carbon dioxide levels.
• According to the latest Assessment Report from
the Intergovernmental Panel on Climate Change, "most of the
observed increase in globally averaged temperatures since
the mid-20th century is very likely due to the observed
increase in anthropogenic greenhouse gas concentrations".
• CO2 is produced by fossil fuel burning and other activities such
as cement production and tropical
deforestation. Measurements of CO2 from the Mauna Loa
observatory show that concentrations have increased from
about 313 ppm in 1960 to about 389 ppm in 2010. It reached
the 400ppm milestone on May 9, 2013.
