Fundamentals• Atmosphere• Climate Variation• Greenhouse Effect• Climate Drivers• Carbon Cycle• Energy Balance• System Inertia• Geologic time• Causes of Climate Change

Earth’s Atmospheric Composition, Temperatures and Pressure

Composition PercentNitrogen (N2) 78

Oxygen (O2) 21

Argon (Ar) 0.93Carbon Dioxide (CO2) 0.038

Water Vapor (H2O) 0-4Sea level Surface Pressure (Bars) 1

Extreme Surface Temperatures (°C)

60 to −130 (Global Mean = 14.6)

Atmospheric Abundance of CO2 and Global Temperatures

CO2 Percent

Average Global

Temperature (°C)

Event0.018 9 Last Ice Age Maximum

0.028 13 Interglacial Period (Holocene)

0.038 14.6 Today

0.045 16 Critical for Humans and Other Species

0.065 18 Catastrophic for Humans and Other Species

~0.15 25 Hot House Maximum

96.5 480 Venus Surface

Climate Shift and Temperature

Natural Variations of Climate during Warming

One Way of Causing Short-term Climate Variations

The Greenhouse Effect

Small changes in the global average temperature result in

large climate changes

• A 5° C drop in the global average temperature places us in the depths of an Ice Age.

• An 8° C rise in the global average temperature places us near the top of a Hot House.

Greenhouse Gases and Percent Warming

• Carbon Dioxide - CO2 (56%)

• Methane - CH4 (16%)

• Tropospheric Ozone - O3 (12%)

• Halocarbons (11%)

• Nitrous Oxide - N2O (5%)

Climate Drivers

Change in Temperature with Height for 2 Amounts of CO2

Continental Absorption of CO2

Energy Balance of the Earth

INERTIA• General Physics…the resistance to

change in some physical property of a body or system.

• Global Warming…the resistance to change in direction of various elements of the climate system, such as rising atmospheric CO2, rising temperatures and melting ice.

Inertia in Action

• CFCs have decreased dramatically during the past 20 years.

• The ozone hole in 2006 was as large as ever because of the long lifetime of CFCs in the stratosphere and continuing emissions.

• It will take about 70 years for the ozone hole to disappear.

Other Climate Basics• Feedbacks can cause the climate

to move in one direction or the other independent of the original cause.

• Abrupt climate changes can drive the climate very rapidly; up to 8° C in 10 years or less.

• Uncertainties

Natural Causes of Climate Change

and

Geologic Time

Geologic Timescale

Red and blue areas indicate hot (Hot House) and cold (Ice House) periods

The Geologic Time Scale Relative to One Year

Eon or Era

Absolute Time Relative to a year

Duration (million years)

Percent Geologic time Starting time Duration

Precambrian 3,996 88.0 January 1 10 mo. 17 d

Paleozoic 296 6.5 November 18 24 days

Mesozoic 183 4.1 December 12 15 days

Cenozoic 65 1.4 December 26 5 days

Major Human Events Relative to One Year

Major EventYears

before present

December 31Starting time Duration*

Human development begins ~7 million 10:30 a.m. 13 hr., 30 min.Homo species begins 2.3 million 7:34 p.m. 4 hr., 26 min.Early Homo Sapiens 400,000 11:14 p.m. 46 min.Homo Sapiens Sapiens (us) 125,000 11:46 p.m. 14 min.Civilization begins (Agriculture) 12,000 11:58:21 p.m. 1 min., 21 sec.Bonze Age begins 5000 11:59:34 p.m. 35 sec.Early writing 4000 11:59:32 p.m. 28 sec.Industrial Revolution (technology) 250 11:59:58.3 p.m. 1.7 sec.Average human lifetime 75 11:59:59.4 p.m. 0.6 sec.Current rapid climate warming 25 11:59:59.9 p.m. 0.1 sec.

*Starting time to the present.

The Anthopocene Epoch• The Anthopocene is a new Epoch

characterized by human-caused major global changes that have altered the Earth in fundamental ways.

• It starts near the beginning of the Industrial Revolution in 1751.

• We are no longer in the Holocene.

Some Major Changes to Earth by Humans

• Changed Carbon Cycle• Climate Change• Ocean Acidification• Urbanization and Habitat

Encroachment• Deforestation• Major Depletion of Marine Food Fish• Major Disruption of Land Surfaces

Beginning of the Anthropocene• The diagram shows

some of the criteria that defines the Anthropocene.

• The effects of these changes will leave a distinct stratigraphic marker.

Mass Extinctions• The K/T extinction was

probably due to a large impact that radically changed the climate.

• The other extinctions appear to be due to natural climate changes.

• The greatest mass extinction (P/T) was due to a climate change from an Ice House to a Hot House.

Causes of Climate Change• Abundance of Greenhouse Gases• Major Volcanic Eruptions• Large Asteroid or Comet Impact• Change in Sun’s Irradiance• Change in Ocean Circulation • Continental Drift• Change in Earth’s Motions

Red = main cause of current global warming

Past Oxygen and CO2 Abundances

Major Volcanic Eruptions• Large volcanic eruptions can cool

the climate for a few years by injecting ash into the stratosphere to reflect the Sun’s radiation back to space.

• Enormous eruptions over long periods can emit large amounts of CO2 to warm the climate.

Mt. Pinatubo eruption lowered the global average temperature between 0.2 and 0.6° C from mid-June 1991 and about 1995

Large Asteroid or Comet Impacts• Large impacts cool the climate by

injecting dust into the stratosphere to reflect sunlight back to space.

• If the impact is in limestone a large impact will first cool the climate and then heat it up by releasing large amount of CO2 from the limestone.

Changes in the Ocean’s Thermohaline Circulation Can Change the Climate

Continental Drift due to Plate Tectonics can Change Climate over Millions of Years

Changes in Earth’s Motions can Change the Climate

Variations in the Earth’s Insolation with Time

Changes in the Sun’s Irradiance

Soar irradiance through September 2008. Reference: Fröhlich, C. and J. Lean, Astron. Astrophys. Rev., 12, pp. 273--320, 2004. http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant

Solar Irradiance Does Not Correlate with Human-caused Temperature Increase

Measurements of Surface Temperature and Sun’s Energy

Solar Irradiance, Temperature, and Atmospheric CO2

Solar Irradiance, Temperature, and Human-Caused CO2 Emissions

Conclusions• Only two causes can operate on time scales short

enough to account for today’s rapid warming: 1) increase in solar irradiance, or 2) increase in greenhouse gases.

• The increase in solar irradiance is not enough to account for the present warming, and does not correlate with its rapid rise.

• The increase in greenhouse gases must be the primary cause of global warming.

• This is consistent with the observed rapid rise in both greenhouse gases and their emission by human activities.