2.Global Warming
CO2 levels in the atmosphere rising
Average global temperature is rising
Polar ice caps and mountain glaciers are shrinking
Sea level is rising
Deserts are expanding
Weather is getting more severe
3.Is this normal?
How can we tell if the present change in climate is normal or something produced by humans?
Is the amount of present climate change normal or is it extreme?
Is there any way to answer these questions?
4.Changing Perspectives
Our perspective: single human life.
Expand to a few other generations.
We need a longer time frame to evaluate global climate change.
5.Geologic Record
Provides us with longer perspective
Contains indirect evidence of climate
Contains direct evidence of climate
Gives us a history of global climate change on a scale of millions of years to billions of years.
6.Indirect Evidence
Evidence for
Aridity
Warm Climate
Cold Climate
Recorded by specific types of rocks
7.Examples: Desert sandstones
8.Examples: Reef Limestones
9.Examples: Glacial Features
10.Direct Evidence
Ice Cores
Sediment Cores
Temperature Proxies
11.Ice Cores
12.Data from Ice Cores
Direct Evidence for last 100,000 years
Quantities of dust in each layer
Related to wet vs. dry climate
Air bubbles trapped in each layer
Samples of ancient air
Levels of CO2
13.Sediment Cores
Deep Sea Drilling Project (DSDP)
Ocean Drilling Project (ODP)
Integrated Ocean Drilling Project (IODP)
Coring in lakes and bogs
14.Data from Sediment Cores
Quantity of mud vs. shelly material
Relates to sea level, climate and weathering on land
Temperature proxies
From Chemical Signatures
From Fossils
15.Temperature Proxies
Stable Isotopes
Not radioactive
Proportions of stable isotopes are dependent on temperature
Ratio of 18O to 16O
Ratio of 13C to 12C
Coiling in microfossils
16.What does theGeologic Record Tell Us?
The “normal” climate of the past 1.0 billion years
Warmer than present
More uniform than present (less fluctuation)
Past 20 million years have been highly variable and generally much colder
17.Climate History:20 Ma to Present
20 Ma – climate was somewhat moderate
Similar to present
5 Ma – coldest climate of past 65 million years
2 Ma – Great Ice Ages begin
At least 4 episodes of glacial advance and melt back
12,000 – 10,000 Modern Climate sets in
18.Recent Climate History
7000-6000 BP - Warm Peak
950-1300’s – Medieval Warm Spell
1300’s – Cool and Wet
1550 – 1850 – “Little Ice Age”
19.Food For Thought
How many of the great events of recorded human history have been directly influenced by climate?
20.Recent Climate History
7000-6000 BP - Warm Peak – Great Ancient civilizations (e.g., Mesopotamia, Egypt)
950-1300’s – Medieval Warm Spell – Rise of “modern” European nation-states
1300’s – Cool and Wet – Bubonic Plague
1550 – 1850 – “Little Ice Age”
Washington crosses the Delaware
Winter at Valley Forge
21.So, are we to blame?
Paleoclimatic record reveals major shifts in climate through time
Is it coincidence or causation that climate is warming as we come out of last ice age?
Is it coincidence or causation that industrial revolution falls within this same time?
22.What factors cause changes in climate?
Long term vs. short term changes
Volcanic eruptions
Earth’s orbital variations