Transcript Global Warming

The Complexity of Global Climate Change
GLOBAL WARMING
1. Introduction to the Greenhouse Effect
 On Earth
 On Other planets
2. Global Warming Today?
 We need a record for comparison
3. Earth has a History of Climate Change
 Measuring climate change
in Earth’s geologic past.
 Climate cycles in Earth’s past.
4. Global Warming Today!
 Why should we care?
 Possible effects.
5. Scientific Uncertainty
 What’s Fact
 What’s Probable
 What’s Uncertain
1. Introduction to the Greenhouse Effect
a. Greenhouse Gases – CO2, Water Vapor, etc.
b. Absorption of long wave radiation
c. Effects on Earth
d. Effects on other planets – Venus and Mars
2. How can we examine past climate?
Isotopes – Varieties of an element
that contain different #’s of neutrons
Hydrogen
0 neutrons
Deuterium
1 neutrons
Tritium
2 neutrons
Oxygen has several isotopes
Isotope
16O
17O
18O
Atomic Mass
Abundance
15.99491463
16.9991312
17.9991603
99.7587%
0.0374%
0.2039%
Seawater (H2O)
has oxygen in it.
Polar Ice is 30 p/mil
Enriched in 16O
Evaporation
from oceans
3. Earth has a History of Climate Change
 Measuring climate change
in Earth’s geologic past.
Microfossil shells preserve ancient
δO18 from seawater.
A record of past temperature
Coccolith
Foraminifera
3. Earth has a History of Climate Change
 Measuring climate change
in Earth’s geologic past.
 Paleothermometry with
Oxygen Isotopes
 Oxygen Isotopes – O16, O17, O18
 Ratio in Water Controlled by
a. Temperature
b. Phase Change (e.g., liquid to gas)
 δO18 ~ O18/ O16
 Cold Climate:
δO18 in ocean
 Warm Climate:
δO18 in ocean
3. Earth has a History of Climate Change
 The δO18 Record
Other Sources of Climate Data
a. Ice Cores – measure the
amount of CO2 and other
greenhouse gases in ice core
bubbles.
Other Sources of Climate Data
b. Pollen – plant species are
sensitive to climate.
Other Sources of Climate Data
c. Historical Records
Winter Landscape by Peter Brueghel, 1601
The Little Ice Age in Holland
3. Earth has a History of Climate Change
 Climate cycles in Earth’s past.
 1st Order – Hot House/Ice House:
Millions of years
2. Earth has a History of Climate Change
 Climate cycles in Earth’s past.
 2nd Order – Glacial/Interglacial:
Thousands of years
2. Earth has a History of Climate Change
 Climate cycles in Earth’s past.
 3rd Order – Years To Hundreds of
Years: The Historical Record
2. Earth has a History of Climate Change
Why are there climate cycles?
Hypotheses a. First Order: Changes in Greenhouse
Effect from Plate Tectonics
b. Second Order: Changes in amount
and distribution of incoming solar
radiation - Milankovitch Cycles
c. Third Order – Sunspots, Volcanism,
Other??
4. Global Warming Today?
 Evidence for and against.
 Atmospheric Rise in CO2
Is The Earth Warming Up?
Evidence For:
 0.6o increase in global temperature
 Sea-level rise of of 4-10” in last century
 Growing season 11 days longer in N.
hemisphere than in 1950’s.
Desertification of the Sahel (subsaharan Africa).
Shrinking of Arctic Ice Pack
Is The Earth Warming Up?
Evidence Against:
 Computer models are inaccurate –
predicted a 2o C rise in temperature.
 Rise in temperatures inconsistent with
CO2 input: T pre-1940; CO2 post1940.
 Satellite measurements show no
tropospheric warming.
 Urban heat Island Effect.
Is The Earth Warming Up?
Rebuttal to Against:
 Computer models are not fortune tellers.
Guides to understanding change and
pointers to areas that need further
study.
 Rise in temperatures greatest in last
decade. 1990’s were warmest decade of
the millenium.
 Satellite measurements are calibrated
incorrectly? Lag time for temperature
change to be recorded in atmosphere?
 Urban heat Island Effect – Much better
data now!
Is The Earth Warming Up?
Rebuttal to Against:
GEOLOGIC DATA
1) Shrinking of Arctic ice pack.
2) Loss of tropical, high altitude glaciers.
3) Melting of permafrost.
4) Break-up of Antarctic ice shelves.
4. Scientific Uncertainty
 What’s Fact
a. The Greenhouse Effect is real
and has operated throughout Earth
History.
b. Atmospheric concentrations of
CO2 are increasing due to human
activity.
 What’s Probable
a. 1 – 3o C Temp rise by 2150
b. Sea-level rise of 10 –30 cm
 What’s Uncertain
a. Effects on ocean/atmosphere
circulation
b. Weather Patterns
c. Effects on Agriculture
d. Runaway Greenhouse Effect?