Climate change and Global Warming Update

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Climate change and Global Warming Update

• CO2, Temperature 100,000 yr Periodicities
• Milankovich effect?
• Solar Cycle Variations?
• Snowball Earth vs. CO2 (600-800 Myr ago)
• But CO2 concentrations were 10x-15x greater than
  today (paleo record)

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Global temperature rapid rise in past 100 years,
1000 yrs
Rapid temperature rise coincident with industrial
revolution (fossil fuel burning)
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Sea levels are rising rapidly
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Global Warming 1 China will pass USA in CO2
emissions in 3 years
But. CO2 emission per capita is still far larger
in USA (1/4 population gt 4x CO2 emission per
person)
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CO2 variations past 500,000 yrs tracks ice-age
cycles
Note that current CO2 concentration is the
largest (by a factor of 2) in last 500,000 yrs
What causes the 100,000 year periodicities?
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Vostok (Antarctica) ice cores dust correlates
with temperature, CO2 variations
CO2 concentration closely correlate with global
temperatures (and dust)
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Recent climate change Global Ice cover (present
and 20,000 yr ago last ice age)
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• Q. Which statement is incorrect?
• CO2 levels are highest during periods of
  glaciation
• There is a 100,000 yr periodicity to both
  temperature and CO2 concentrations
• The present atmospheric CO2 concentration is
  twice as high as at any time the past 500,000 yrs
• Ice core samples show increased dust
  concentration just before periods of glaciation
• Global sea levels have risen 20 cm in the past
  120 yrs.

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• Do Earths orbital variations drive long-term
  climate change?
• Milankovich cycles

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Milankovich effect

• Earth orbital parameters ellipticity, obliquity,
  precession vary periodically

Obliquity, P40,000 yr (22.1- 24.5, now 23.5)
Eccentricity, P413,000 yr (0.005 0.058,now
0.017)
Precession, P26,000 yr Change in orientation of
spin axis of Earth
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Variation in orbital parameters over 400,000 yrs
Now
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Changing ellipticity How does this change solar
insolation and temperature?
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Does solar forcing due to orbital variations
correlate with the glaciation record?
Compare these plots
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Variation in Solar Insolation (tan plot) vs.
temperature metrics
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• Solar luminosity variations
• driver for climate change?

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Are solar variations (partly) driving increasing
global temperatures?
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Sunspot activity over 400 yrs
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How much solar flux increase is required to
explain temperature rise in last century?

• Last 100 yr has seen ?T 0.8C
• Range in Lsun is 1 W for solar max to solar min
• Differentiate T(L) L1/4 gives
• ?T/T ¼ (?L/L)
• ?L/L 1/1367 0.00073
• So ?T/T 0.00018
• So ?T 0.045C
• This is only 6 of observed change

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• Long term climate changes (500 Myr)

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Snowball Earth ages
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Long-term history of CO2 concentration (550 Myr
ago- present)
CO2 levels are 10x-15x present values!
(model-dependent)