Transcript SNC2D_03_08_Evidence_and_Consequences

Evidence of Global Warming
and Consequences
Average Global Temperatures are Rising
• Current climate data (past few hundred years) is
more accurate due to the technology enabling the
collection, but only gives short term information.
Greenhouse Gases are Increasing
• Direct atmospheric and ice
core measurements show
greenhouse gas levels have
been rising since the 1700s.
• This corresponds to the
start of the “Industrial
Revolution”.
Tree Ring Analysis
• The growth rings of trees are used to determine
relative temperature and amount of rainfall in the
years the tree has been living.
• Larger spaces between rings
shows warmer, wetter years.
• Small spaces between rings
could mean warm, but dry
or could simply mean cool
conditions for that year.
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Sedimentary Rock Analysis
• The layers of rock sediments in the Earth and their
composition provide insight into former climates.
• Carbon isotopes are used to
date the age of the sediments,
as well as indicate how much
carbon was being cycled in the
world (evidence of higher
global temperatures) at those
times.
• This can go back millions of
years.
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Global Temperature Changes
• Earth’s temperatures have fluctuated.
• Scientists do not fully understand all the reasons behind the
warming and cooling periods of the Earth.
• Climate data a very long time ago provides a broader view of
the climate history of the Earth, but can only be obtained
through methods of inference.
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Global Consequences
A positive feedback loop is a sequence of events
that cycles back to enhance an outcome.
One major concern is that the impacts of
climate change will further enhance the process.
Cause
Effect
Deforestation Feedback Loop
Forests are important carbon sinks.
Absorb CO2 and convert it into sugar by
photosynthesis:
6CO2 + 6H2O
C6H12O6 + 6O2
sugar
Logging and agriculture reduce global forests.
Climate change may speed this up.
Global temperatures
increase and
precipitation
decreases.
Carbon dioxide
increases the
greenhouse effect.
Deforestation occurs
due to fire, drought
and insects.
Carbon dioxide
released back into
the atmosphere.
Albedo Feedback Loop
• Albedo: measures
the amount of light
reflected by an
object.
• Clouds and ice have
a high albedo - they
reflect, not absorb,
sunlight.
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Global
temperature rises.
Decreased albedo
means more heat
is absorbed.
Permanent sea ice
and glaciers melt.
Darker ocean
water and land is
revealed.
“Soda Pop” Feedback Loop
Analogy…for CO2
A warm bottle of pop is more “fizzy” than a
cold one…
– Carbonated beverages contain dissolved CO2
– At high temperature, less CO2 can dissolve in
the pop.
– When the pop is opened, CO2 begins to escape
by forming bubbles.
Global
temperature
rises.
CO2 levels
rise in the
atmosphere.
Less CO2 can
dissolve in
the oceans.
Negative Feedback Loops
Negative feedback loops exist too:
1. Higher temperatures and more CO2 may
stimulate photosynthesis, decreasing CO2.
2. Increased evaporation due to global warming
may cause more cloud formation, resulting in a
higher global albedo and global cooling.
Global Warming vs. Climate Change
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