Things to Ponder

1. Why are polar bears often used to illustrate climate change?

2. What is the atmosphere?

3. What are the primary layers of the atmosphere?

Chapter 23

The Atmosphere, Climate and Global Warming

Climate Change Central Questions & Key Concepts

• What is the atmosphere?• What is the difference between weather & climate?• How does the Earth’s climate fluctuate?• What factors affect climate?• What are the possible effects of global warming?• What can humans do about potential climate change?• Ozone depletion and global warming are two very

different things.

The Atmosphere

• The thin layer of gases that envelops the Earth• Chemical reactions• Atmospheric circulation produces weather and

climates

The Atmosphere

by weight thickest layer

weather

Very little water

Processes That Remove Materials from the Atmosphere

• Sedimentation: – Particles that are heavier than air settle out as a result of gravity.– Ex: Coal /volcanic particles will settle out over time

• Rain out:– Precipitation will physically and chemically flush materials from the

atmosphere.– Ex: CO2 + H2O H2CO3 carbon dioxide is removed

• Oxidation:– Where oxygen is chemically combined with other substances. – Ex: atmospheric sulfur dioxide oxidizes to form sulfur trioxide

which produces sulfuric acid• Photodissociation:

– Solar radiation can break down bonds in this chemical process. For example ozone may break down due to this process from O3 to O2.

Vocabulary Used to Characterize Air• Pressure:

– force per unit area• Atmospheric pressure:

– is the weight of overlying atmosphere per unit area– Question: Does the atmospheric pressure increase as

altitude increases or does it decrease?• Temperature:

– a measure of thermal energy, ie the kinetic energy of the motion of atoms in a substance.

– Question: as temperature increases does kinetic energy increase or decrease?

• Water vapor: – The amount of water vapor present in a particular place

depends on several things including air temperature, air pressure and available water vapor (from various processes – remember the water cycle?)

Weather vs. ClimateNOT THE SAME THING!!

• Weather: – Weather is what conditions of the atmosphere are over

a short period of time, (hours, days, weeks)• Climate:

– climate is how the atmosphere "behaves" over relatively long periods of time (seasons, decades)

– that “behavior” includes the representative or characteristic atmospheric conditions for a region on Earth

• Microclimate– The climate of a very small local area

Short Term Climate Variation

• In addition to long-term climate change, there are shorter term climate variations.

• This so-called climate variability can be represented by periodic or intermittent changes related to El Niño, La Niña, volcanic eruptions, or other changes in the Earth system.

El Niño/Southern Oscillation (ENSO)• Natural. Occurs every 5-10 years. Last 12-18 months• A disruption in the natural weather circulation

– The trade winds that usually blow warm surface water towards the western edge of Australia and Indonesia, and nutrient rich cold water (good for fish) towards the west coast of South America weaken or change direction totally.

– Causes small changes in ocean temperature that in turn cause very large changes in global weather patterns.

• Events believed to have been caused by El Nino:– drought conditions in Indonensia, Africa and Australia.

Flooding in South America as well as 1993 Mississippi and 1995 California floods,

• So what is La Niña

Normal El Niño

Major Climatic Change

• Major climatic changes have occurred during the past 2 million years

• Appearances and retreats of glaciers• During the past 100 years, the mean global

annual temperature has increased by .5 degrees Celsius

The Greenhouse Effect

• Greenhouse Effect– The process of trapping heat in the atmosphere

• NATURAL!• Without it the world would be too cold to support life!

– Water vapor (85% of greenhouse warming), water particles (12%) and several other gases warm the Earth’s atmosphere because they absorb and emit radiation

• Greenhouse Gasses– Gasses that have a greenhouse effect– Water vapor – Anthropogenic sources: carbon dioxide, methane, nitrous

oxide, CFCs (page _____)

The Natural Greenhouse Effect

Albedo: known as surface reflectivity of sun’s radiation

Changes in the Earth’s Temperature During the

Past Million Years

• The mean average temperature of the Earth has swung up and down by several degrees Celsius over the past million years due to variations in the Earth’s orbit around the sun.

• Interglacial periods – Times of relatively ice free periods, whereas times of low temperature reflect glacial events.

• Global climate can also change in shorter times – ex: continental glaciation ended 12,500 years ago with rapid warming – only lasting a few decades.

So what is “Global Warming”• A natural or human induced increase in the average

global temperature of the atmosphere near the earth’s surface

• 4 factors– Amount of sunlight Earth receives– Amount of sunlight Earth reflects– Retention of heat by atmosphere– Evaporation and condensation of water vapor

• Negative and Positive feedback cycles affect the atmosphere

• Increase in emission of greenhouse gasses• Solar Forcing, Natural Cycles, Aerosols (global

dimming), Volcanic Eruptions, El Nino

• Climate models• Apparent influence

of human activities• Could be natural

changes

Projecting Future Changes in Earth’s Climate

Evidence for Global Warminghttp://climate.nasa.gov/evidence/

• Sea level rise– Global sea level rose about 17 centimeters (6.7 inches) in the last century.

The rate in the last decade, however, is nearly double that of the last century.• Global temperature rise

– All three major global surface temperature reconstructions show that Earth has warmed since 1880. The 2000s had a solar output decline but still warmed.

• Warming oceans– The oceans have absorbed much of this increased heat, with the top 700

meters (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969.

• Shrinking ice sheets– The Greenland and Antarctic ice sheets have decreased in mass. Data from

NASA's Gravity Recovery and Climate Experiment show Greenland lost 150 to 250 cubic kilometers (36 to 60 cubic miles) of ice per year between 2002 and 2006, while Antarctica lost about 152 cubic kilometers (36 cubic miles) of ice between 2002 and 2005.

Evidence for Global Warminghttp://climate.nasa.gov/evidence/

• Declining Arctic sea ice– Both the extent and thickness of Arctic sea ice has declined rapidly over the

last several decades• Glacial retreat

– Glaciers are retreating almost everywhere around the world - including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa

• Extreme events– The number of record high temperature events in the United States has

been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events.

• Ocean acidification– Since the beginning of the Industrial Revolution, the acidity of surface

ocean waters has increased by about 30 percent. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.

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• Warming stimulates algae growth.– Algae absorbs CO2.

• Warming stimulates plant growth.– Plants absorb CO2.

• Polar regions receive more precipitation from warmer air carrying more moisture– Increased snow and ice could cause the solar energy to be

reflected causing cooling

• Increases in water evaporation from the ocean and the land could increase clouds.– The clouds reflect the sunlight and cool the surface.

Negative Feedback Cycles Associated with the Greenhouse Effect

• Increased evaporation– Added water vapor in the air that does

not condense will cause additional warming.

• Melting permafrost at high latitudes– Releases methane, as a by product of decomposition of organic

materials in the melted permafrost layer, which would cause additional warming. Releasing old carbon locked in the soil..

• Reduction in the amount of snow pack– Replaced by darker vegetation/soil could increase absorption

of solar energy further warming the Earth’s surface.

• Increased use of air conditioning in warmer climates– Increased use of fossil fuels could increase release of CO2.

Positive Feedback Cycles Associated with the Greenhouse Effect

Old Carbon vs. New Carbon

• Old carbon can be defined as carbon that is trapped and not currently part of our current carbon cycle.– In fossil fuels – released through burning.– In Arctic Soils – being released as temperatures

increase.• New carbon is carbon that is part of the

current carbon cycle. It has recently entered the soil through vegetation. – Biofuels release CO2 but it is NEW carbon

Factors Affecting Changes in Earth’s Average Temperature

• Changes in solar output• Changes in Earth’s albedo• Moderating effect of

oceans• Clouds and water vapor• Air pollution

Climate Change and Human Activities

• Increased use/burning of fossil fuels– Adds ~ 5.5 gigatons per year to the atmosphere. The carbon

combines with oxygen to produce CO2

• Deforestation – Adds ~ 1.6 gigatons per year to the atmosphere. Burning of the

trees releases carbon stored in the wood that combines with oxygen to produce CO2

– Not to mention the fact that the trees are no longer taking IN CO2!

Effects of Global Warming

• Changes in climatic patterns• Melting icecaps & glaciers• Rise in sea level• Coral reef bleaching• Changes in biosphere

Some Possible Effects of a Warmer World

Solutions: Dealing with the Threat of Climate Change

Options:• Do nothing• Do more research• Act now to reduce

risks• Precautionary

Principle

Treeplantation

Coalpower plant Tanker delivers

CO2 from plantto rig

Oil rig

Crop field

Switchgrassfield

Spent oil reservoir isused for CO2 deposit

CO2 is pumpeddown to reservoir through abandoned oil field

Abandonedoil field

CO2 is pumped downfrom rig for Deep ocean disposal

= CO2 deposit

= CO2 pumping

Removing CO2 From the Atmosphere

Reducing Greenhouse Gas Emissions• European Climate Exchange: Carbon Trading

– A nation will agree to cap its emissions– Corporations are issued emission permits that allow X

amount of emissions. These can be traded.

• Rio Earth Summit (1992)– Rio de Jeneiro, Brazil: Blueprint for reduction of CO2

emissions. USA disagreed said it was too costly.

• Kyoto Treaty (1997)– Legally binding emission limits discussed.– 166 nations signed. USA refused to sign, though eventually

agreed to cut emissions 7% below 1990 levels. Recommended levels were 60-80%.

Reducing Greenhouse Gas Emissions Continued…

• G-8 meeting (2008)– New U.N. treaty to be discussed in Copenhagen in

2009. Leaders including USA agreed to consider and adopt reductions of greenhouse gas emission of at least 50%.

• Facts:– United States has 5% of the world’s population,

yet emits 25% of the atmospheric CO2. – California by ITSELF is 12th in the world for CO2

emissions. CA, however, passed legislation in 2006 to reduce emissions by 25% by 2020.

The ozone hole is a completely different phenomenon to global warming!There are links between them.

For next time: What are those links?