Climate Change and Ozone Loss
Chapter 20
The Greenhouse Effect
• We know that short wave radiation from the sun
passes through the air to earth with little
difficulty, excepting that clouds and certain
pollutants reflect sunlight back into space. The
radiation that reaches the ground/water warms it
and then is reradiated as long wave radiation.
This long wave radiation is slow to escape
through the atmosphere and therefore keeps us
considerably warmer. (Thankfully! We would be
at -18ºC otherwise, bbhhuuurrrr!)
Do you know?
1. What are the four most important greenhouse
gases?
2. Which gas is believed to be most directly
responsible for global warming?
3. How much is the earth expected to warm in
this century?
4. What are three things that make global
warming effects hard to predict?
Greenhouse gases
• Water vapor is the most important, but is variable and
hard to determine if we impact directly
• Carbon dioxide is the largest of the manufactured
gases, mostly from burning fossil fuels
• Ozone is a greenhouse gas in the troposphere
• Methane from the anaerobic breakdown of organic
matter
• Nitrous Oxide (N2O) – from smog and nylon
production, burning coal and biomass
• CFCs in the troposphere act as a greenhouse gas
Global Warming
• Carbon dioxide has been steadily increasing
over the last forty years and many scientists
believe that global warming is occurring due to
increased amounts of this gas
• Source- Canadian Climate Center, Hadley
Center (UK), Intergovernmental Panel on
Climate Change
• 1990 was the hottest decade on record
(coincidence?)
How hot will we get?
• Scientists believe that we will
increase between 1 – 3.5ºC or
1.8 – 6.3 ºF (now that’s hot)
• Realize that a 1ºC increase
would make the planet hotter
than it has been in 10,000 years
Why is global warming hard to
predict?
• Solar output varies
• Oceans absorb unknown amounts of energy
• Clouds reflect light and will vary with changing
moisture content in troposphere
• Ice reflects light and will change with
temperature and precipitation
• Global weather/climate pattern are not fully
understood
Global warming effects
• Warmer oceans will release stored up carbon
dioxide further warming planet
• Melting ice will not reflect sunlight further
warming planet
• Melting permafrost will release trapped methane
further warming planet
• Positive Feedback Loops!!!
Global warming effects
• Warmer oceans may have different current
patterns
– Disrupts “normal” weather patterns causing
increased weather related catastrophe
– Can kill reef/fish ecosystems
– Change wind patterns shift pollution to new areas
Global warming effects
• With increased carbon dioxide some plants may
flourish reducing/removing carbon dioxide from
the air, but as they decompose they release
more methane into the air
• The world’s ecosystems are too complex for us
to properly model on computers at this time