GEOL-1010 Lecture Notes - Lecture 10: Continental Crust, Solar Irradiance, Global Cooling

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5 Feb 2018
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Lecture 10: Global Warming
Geology in the News
Another new piece of continental crust found
Scientists are using updated mapping techniques that is helping them identify features that
you can’t just see
Part One: Is the Earth Warming Up?
Why Do We Care About Global Warming
Why do we care?
o It relates to nearly everything
Hypotheses
Facts- have to be able to demonstrate as a truth
Opinions- you can have whatever opinion you want, you don’t have to have facts to back
it, BUT they don’t hold up. Scientists have to rely on facts.
Global Warming
2 separate questions to disentangle
o 1. Is the Earth warming up?
Have to address this one before the second one
o 2. If so, why?
SO Is Earth Warming Up?
Temperature calculations can get confusing
o Different places, statistical averages, etc.
Use a proxy instead
o Proxy= substitute
o Lots of things in nature respond to temperature change
o Example: Glaciers
If it is getting warmer- glacier melts and gets smaller
If temperature stays the say- glacier stays the same size
If temp gets colder- the glacier gets thicker
o 1980 vs 2002
Glacier in 1980 filled the entire valley, in 2002 it had almost disappeared
Glaciers Around the World
Warm colored dots are where glaciers have gotten smaller
Cool colored dots are where glaciers have been getting thicker
Bigger the dot the bigger the change in size
For the most part, glaciers across Earth have been getting smaller
Save to say places have been getting warmer in recent times
Part Two- Why is Earth Warming
More than one reason
Earth is currently naturally warming
o Earth is still kind of coming out of the most recent ice age
o Ice age was only 10,000 years ago which really isn’t that long
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Natural processes (ex-Milankovich cycles) account for ~50% of warming over the past few
centuries
Unusual Warming Pattern
The warming is occurring faster and has a greater magnitude than other warming trends we
have data for in recent history
Greenhouse Gases and Global Warming
Remember GGs trap insolation
Is the amount of GG in the atmosphere increasing??
o Slide 14- there is a buildup of GGs
Is the amount of escaping insolation decreasing?
o Yes. It has been steadily declining since the early 70s
So yes… greenhouse gases are a part of the problem
Conclusion: ~50% of the temperature increase in the last 250 years is due to greenhouse
gas buildup
o The other 50% is natural processes
To argue against this, you have to have a better hypothesis that is consistent with the facts
o Proof NOT belief
o If you don’t have any facts to support you, its no good
Humans and GGs
Fossil fuel burning since the Industrial Revolution has added the GGs to the atmosphere
Is the GG buildup anthropogenic?
o Aka is it caused by humans?
o Anthro- humans
o Geniuses- origin
Human population has been growing rapidly
o That is a huge number of people that need energy
CO2 Buildup (400k yr record)
No increase similar to the current one
Does not prove where the CO2 has come from
In the past century it has gotten VERY high
o Made people suspicious that human activity has caused this sudden increase
o Slide 18 graph does NOT prove that humans caused
o Just because it is after the industrial revolution doesn’t prove humans caused it, it
just shows a trend
o Need more detail
Finding the Carbon Source
3 isotopes of carbon
o Carbon 14- radioactive
o Carbon 12 and 13- stable
o We’re looking at the Ratio of Carbon 14 to Carbon 12
Investigate which carbon isotopes are building up
Seuss Effect: the drop in the ratio. The decrease in the C14 to C12 Ratio
14C/12C- ratio
How do you decrease the 14C/12C Ratio?
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