Transcript Global Warming

THERMOHALINE CIRCULATION:
THE GREAT OCEANIC CONVEYOR BELT
The Movie Story
NOT CORRECT!
Air is pulled down in a high pressure system
This causes warming and nice weather!
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. Scientific Uncertainty
 What’s Fact
 What’s Probable
 What’s Uncertain
5. Global Warming Today!
 Why should we care?
 Possible effects.
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
VENUS
MARS
EARTH
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
2. 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
2. 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
2. Earth has a History of Climate Change
 The δO18 Record
Other Sources of Climate Data
a. Ice Cores
Other Sources of Climate Data
b. Pollen
Other Sources of Climate Data
c. Historical Records
Winter Landscape by Peter Brueghel, 1601
The Little Ice Age in Holland
2. 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
The Pleistocene Epoch:
1.8 million to 10,000 years ago
A Much Different World
North America During the Pleistocene
What If Today’s Glaciers Melted?
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??
3. Global Warming Today?
 Evidence for and against.
 Atmospheric Rise in CO2
GLOBAL TEMPERATURES?
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?