1.Greenhouse Effect 2.The CO 2 Cycle, Long-Term Climate Change 3.Ice Ages and Short-Term Climate Change 4.Human-Induced Climate Change

Global Climate History Geologic evidence clearly indicates relative long-term climate stability that has allowed liquid H 2 O to exist for most of geologic history.

The Earth’s Climate System - very complex!!

Earth’s Atmosphere 77% N 2, 21% O 2, 1% Ar, + trace gases (CO 2, CH 4, H 2 O) Absorbs incoming solar radiation and warms the planet. Important component of global climate.

Without atmosphere, average Earth temperatures would be a cool –17°C!!

The Greenhouse Effect

Greenhouse effect gives +32°C warming and allows for liquid H 2 O to exist on the planet

The Greenhouse Effect CO 2, CH 4, N 2 O, CFC’s, O 3, H 2 O vapor

1.Greenhouse Effect 2.The CO 2 Cycle, Long-Term Climate Change 3.Ice Ages and Short-Term Climate Change 4.Human-Induced Climate Change

What regulates the amount of CO 2 ?? The concentration of greenhouse gases, particularly CO 2, is important global climate regulation

The CO 2 Cycle Sources: volcanism, metamorphism, respiration, fossil fuel burning, deforestation Sinks: photosynthesis, rock weathering, carbonate depsoition, ocean adsorption

Increased volcanism inputs huge quantities of CO 2 into the atmosphere = T° increases The CO 2 Cycle as Earth’s Thermostat T° increase causes increased chemical weathering and marine carbonate deposition which lowers atmospheric CO 2

Feedback is not instantaneous! Perturbations in CO 2 cycle take on the order of 500,000 years to restore. The CO 2 Cycle as Earth’s Thermostat

Long-Term Climate Change Tectonics plays an important role in regulating atmospheric CO 2 and therefore climate

Mechanisms for Long-Term Climate Change 1.Geographic Arrangement of Continents 2.Amount of Volcanic Activity 3.Uplift of Large Mountain Ranges Mid Cretaceous Warm Period

Increased Mid-Cretaceous Volcanic Activity

Mechanisms for Long-Term Climate Change 1.Geographic Arrangement of Continents 2.Amount of Volcanic Activity 3.Uplift of Large Mountain Ranges (Himalayas, Tibetan Plateau) Cenozoic cooling

Uplift of Himalaya Mtns and Tibetan Plateau Indian Plate (continental) Eurasian Plate (continental) Exposure of large volume of crust increases chemical weathering and lowers atmospheric CO 2

1.Greenhouse Effect 2.The CO 2 Cycle, Long-Term Climate Change 3.Ice Ages and Short-Term Climate Change 4.Human-Induced Climate Change

Major Ice Ages in Earth History 2,000,000 million years to present The classic “Ice Age”

COLD WARM Short-Term Climate Change Climate change over short time scales (<1,000,000 years) Related to complex, poorly understand interactions between atmosphere, hydrosphere, and lithosphere

Last Ice Age was ~6  C colder than present temperatures Last glacial

The Last Ice Age Northern NJ was covered by ~1 km thick ice sheet 30% of the land surface was covered by ice (only 10% is covered today)

COLD WARM Possible Causes 1.Orbital Parameters of the Earth 2.Changes in Atmospheric Composition 3.Changes in Ocean Circulation 4.Sunspot Activity 5.Changes in Reflectivity (albedo) Short-Term Climate Change Climate change over short time scales (<1,000,000 years) Related to complex, poorly understand interactions between atmosphere, hydrosphere, and lithosphere

Orbital Parameters Cause variations in solar radiation with times scales <100,000 years

Radiation variation from summed orbital parameters matches the timing of warm and cold periods on Earth

1.Greenhouse Effect 2.The CO 2 Cycle, Long-Term Climate Change 3.Ice Ages and Short-Term Climate Change 4.Human-Induced Climate Change

Atmospheric CO 2 Data Ice Core Data Direct Measurements, Hawaii

Recent Global Warming

GCM Models of Continued Global Warming between 1995 and 2050

GCM Models of Continued Global Warming

Is plate tectonics required for life? not likely for the origin of life HOWEVER…. crucial for maintaining long-term climate stability which is important for evolution of complex life.