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

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. GLOBAL WARMING

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

Isotope Atomic Mass Abundance 16 O % 17 O % 18 O % How can we examine past climate? HydrogenDeuterium Tritium 0 neutrons1 neutrons 2 neutrons Isotopes – Varieties of an element that contain different #’s of neutrons Oxygen has several isotopes

Seawater (H 2 O) has oxygen in it. Evaporation from oceans Polar Ice is 30 p/mil Enriched in 16 O

2. Earth has a History of Climate Change  Measuring climate change in Earth’s geologic past.  Microfossil shells preserve ancient δO 18 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 – O 16, O 17, O 18  Ratio in Water Controlled by a. Temperature b. Phase Change (e.g., liquid to gas)  δO 18 ~ O 18 / O 16  Cold Climate: δ O 18 in ocean  Warm Climate: δ O 18 in ocean

2. Earth has a History of Climate Change  The δO 18 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.  1 st Order – Hot House/Ice House: Millions of years

2. Earth has a History of Climate Change  Climate cycles in Earth’s past.  2 nd 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.  3 rd 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 CO 2

GLOBAL TEMPERATURES?

4. Scientific Uncertainty  What’s Fact a. The Greenhouse Effect is real and has operated throughout Earth history. b. Atmospheric concentrations of CO 2 are increasing due to human activity. What’s Probable a. 1 – 3 o 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?