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Global Warming


The Earth is growing warmer, the change is not normal and is not caused by the ... long lengths of time during the Cretaceous period from about 145,000,000 years ... – PowerPoint PPT presentation

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Title: Global Warming

Global Warming Or, preferably we would say,
Global Climate Change The Earth is growing
warmer, the change is not normal and is not
caused by the usual factors that have caused
climate change in the past. It is highly likely
(90 probability or greater, according to the
consensus of climatologists) that the cause of
the change is human activities specifically,
the release of large amounts of carbon from
fossil fuels, and other industrial practices
including manufacture of cement, and agricultural
practices. This is called anthropogenic forcing.
Scientists from all over the world have studied
this process and reported on it in hundreds of
scientific meetings and thousands of carefully
reviewed articles published in leading scientific
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There are several different ways to calculate the
warmest year but no matter which method is
used, it is evident that recent years have been
consistently among the warmest ever recorded.
According to NASA, the top five warmest years
were 2005, 2006, 1998, 2002 and 2003
(this data is from the National Oceanic and
Atmospheric Administration of the US government
(note that this is rate so, what does this
graph show! )
Goddard Space Flight Center NASA data, official
US government records
What Controls Global Climate? Past Natural
Changes? How do we know there was different
climate in the past? What may have caused the
natural changes? Why do we think the current
changes are not natural?
Graphic of the Earths Orbit around the Sun
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Auckland is latitude 36 S, Churchill is latitude
58 N, about twice as far from the Equator
Milankovitch published a series of papers in the
1920s which calculated the impact of changing
angles of sun and earth. His conclusion was that
the change in the amount of sunlight falling on
the northern hemisphere at about 65 degrees
latitude (the area where glaciers started) was
the key influence on glaciers and ice ages. By
his calculations and subsequent calculations, no
major change in the solar energy at 65 degrees
should occur for about another 50,000 years. In
his lifetime the data supporting his theories was
incomplete, but in the years following his death
much more accurate and complete data became
available and was explained in a series of
articles written in the 1970s. Milankovitch, M.
1920. Theorie Mathematique des Phenomenes
Thermiques produits par la Radiation Solaire.
Gauthier-Villars Paris. Milankovitch, M. 1930.
Mathematische Klimalehre und Astronomische
Theorie der Klimaschwankungen, Handbuch der
Klimalogie Band 1 Teil A Borntrager Berlin.
Milutin Milankovitch 1879 -1958, Serbian engineer
and mathematician
The three Milankovich cycles a) eccentricity
how elliptical is the orbit b) precession is
the north pole pointed towards or away from the
sun when the earth is closest and farthest from
the sun and c) tilt is the earth perpendicular
to the sun, or tilted over.
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Notice that the distance to the sun is actually
further in summer than winter
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Because each of the Milankovitch cycles has its
own time schedule, it is quite hard to see the
direct relationship. You have to calculate out
the impact of all the cycles together to
coordinate them to the glacial ice ages. The
yellow line of combined solar energy at 65
degrees north latitude correlates pretty well
with the Ice Ages, except for the ones at 500 and
700 m years ago, where the least amount of solar
energy correcsponds to the shortest and least
intense interglacial warm periods.
  • What evidence exists that global change has
    happened or is happening now?
  • Geological evidence
  • - Meteorological evidence

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How much has North America been flooded in the
past? This map shows areas that were covered by
ocean for very long lengths of time during the
Cretaceous period from about 145,000,000 years
ago to 65,000,000 years ago. Over these long
periods the changes in sea level relative to the
continents can be due to motion of the continents
themselves rather than sea level change but
evidence shows that sea level can change on the
order of 300 to 400 meters even within much
shorter periods.
The caves at Cosquer near Marseilles, France were
explored just a few years ago. French
archeologists hypothesized that if sea levels
were lower in ancient times, then neolithic
people could have entered caves now covered by
the sea. When they explored caves along the
Mediteranean coast, they did indeed find caves
where the cave entrance is now 40 meters below
the surface of the sea, but which have paintings
in them drawn by Neolithic artists 30,000 years
ago -- very strong proof that in human history
during the Ice Ages - the surface of the sea was
substantially below the current level.
World flooded to 60 meters
UK and Ireland Flooded to 100m
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USA flooded to 100 meters
OK, so this evidence is strong proof that there
can be massive climate change. But, why do we
think that the current changes are unnatural
why cant the changes that are happening now just
be part of some natural cycle, like sun cycles or
glacial ice ages? One set of evidence that has
been presented very often by people who want to
disprove the idea of Global Climate Change is
related to changes in the amount of heat coming
from the Sun. If the Sun is getting warmer, then
the Earths climate may be changing because of
that, rather than because of human effects from
Carbon dioxide, etc.
I have seen this chart presented at anti-global
warming meetings on two occasions. It shows the
increase in heat from the sun over the last 400
years If the Suns heat has increased by a lot,
then that may be the cause of the Earths
warming. Just a natural event that has nothing to
do with humans? The chart is accurate, but is
it truthful?
Solar radiation This is the exact same chart
as in the previous slide, except that the
vertical scale has been squished down into a
smaller printed space. It shows exactly the same
numbers. This is why you have to read the labels
on every graph before you determine what it
means!!! In this case, the lowest value for
heat from the Sun was in about year 1680
1363.4, and the highest value was in 1980
1366.8. Thats a change of 3.4 / 1363.4 or
0.0025 increase.
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Since the beginning of this course we have said
the same thing over and over Science is
empirical if you want to learn about the Earth,
you have to look at the Earth
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Upsaala Glacier, Patagonia, South America, 1928
vs 2004
So, there is very good evidence that the Earth is
changing its climate. And our understanding of
the natural cycles that can sometimes affect the
climate suggests that this change is NOT just the
kind of natural event that has affected climate
in the past. So, WHAT IS IT that is causing the
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Historic data taken from ice cores that extend
200,000 years into the past suggest that the
highest CO2 levels before modern times were about
200 ppm
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Whats so bad about climate change? Yes, it
looks like rising sea level means that we are
going to lose Florida and Manhattan, but that
isnt going to happen for 100 or 200 years! So,
why worry about it now? Disease? Water? Food? Bio
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Deaths from Global Warming Changing temperature
can drastically affect rainfall and farming.
Areas where farmers have grown crops for
centuries may have to completely alter their
farming practices populations can suffer from
food insecurity Rising temperature can have a
big impact on the growth and survival of germs
and insects that carry germs. Diseases like
malaria, cholera, and many others survive better
and can be more easily spread on a warmer planet.
People who are poorly nourished can fall victim
to diseases more easily.
Dr K Miller of the National Center for
Atmospheric Research has gathered a large
collection of data to predict changes in water
supplies in the various water zones of North
America. The data predicts increasing frequency
of droughts in region 6. This would be bad
Areas which would be liable to suffer water
shortages as a result of a global increase in
temperature. This chart is very uncertain,
however, as weather changes are extremely
difficult to predict.
The main biomes and sub-biomes of North America.
If the temperature and rainfall change
significantly, it basically means that all these
plants might be living in the wrong place. In
the past during natural climate changes the
changes were very slow, so plants and animals
could migrate North or South. The current problem
is happening much too fast for that kind of
migration to take place
Why wont people react to this issue and take
action to solve it? Fill up your gas tank once a
week with about 12 -14 gallons of gas. Thats
roughly 100 pounds of gasoline. Or, 84 pounds of
Carbon and 16 pounds of Hydrogen. The 84 pounds
of Carbon will combine with 224 pounds of Oxygen
to make 308 pounds of Carbon dioxide. Fifty two
weeks times 308 pounds per week would leave you
emitting 16,016 pounds or about 8 tons (7 metric
tons) of CO2 per year from your car. The amount
of CO2 that is emitted by the power plant in
order to provide you with electricity, is
probably roughly the same. So each of us is
responsible for emitting about 16 tons of CO2 per
year. possibly because we are the cause, and
we dont want to change.
Is there an answer? We have an opportunity to
begin a shift to new technologies that do NOT use
Carbon based fuels such as coal, gasoline,
natural gas We can generate our power from wind,
sun and waves. And drive cars that use renewable
fuels Many of the technologies already exist
It is a choice.