Agenda 5/2

Bell-ringer: What is one example

of how the global climate is

changing?

Collect old BRs

Go over exam

Begin notes

Wrap-up: How is climate

different from weather?

Weather

Describes the atmospheric conditions at a

particular place and point in time

Also describes how they change from day to day

Described by a series of measurements such as

temp., precip., wind speed, cloud cover, and

humidity

Example: Costa Rica vs. New

England

Costa Rica near the equator

Temp is always consistently warm

Daily temps fluctuate only a few degrees on average throughout the year

New England far from the equator

Temperatures can vary by as much as 50 degrees Celsius from July to January

Dramatic changes are possible from one day to the next

“If you don’t like the weather, just wait a few hours…”

Climate

The annual repetition of weather patterns

Represent the average weather conditions over

a long period of time

Ex.) November 3rd, 1957

Weather: Exact temp that day

Climate: Average temp on Nov. 3rd from 1851-2006

Climate Change

A shift in the long-term average weather

This shift may generate:

Warmer or cooler temperatures

More or less precipitation

Higher or lower humidity

Stronger or gentler winds

A Changing Climate Climate may appear stable over your lifetime, but

this stability disappears when scientists

compare temperature and precipitation over

longer periods

During some periods Earth was warmer than it is

today, during some periods it was cooler than it

is today

Ice Ages

Most recent Ice Age lasted from 30,000 years ago until 12,000 years ago

Huge sheets of ice covered much of Europe and North America

Ice covered what is now Chicago

Only during the last 10,000 years have the ice sheets shrunk significantly

Retreat of ice sheets corresponds to the beginning of agriculture and evolution of complex human societies

Past 1,000 Years

Climate has warmed and cooled several times

Temps were relatively warm during the medieval

warm period

Temps were relatively cold during the little ice age

of 1300-1860

Agenda 5/3

Bell-ringer: How far south did the ice sheets

reach down to in the last ice age (in N.

America)?

Little Ice Age Video

Notes

Wrap-up: How do volcanoes affect the climate?

Heat Balance The difference between the amounts of energy

that enter and leave the atmosphere

Causes climatic warming and cooling when the

planet’s heat balance changes

Causes of Cooling

Once solar energy reaches the outer

atmosphere, the amount of energy that reaches

Earth’s surface is determined by the

composition of the atmosphere

Clouds reflect sunlight

Increase in clouds reduces the amount of solar

energy that reaches the surface

Aerosols

Tiny solid particles or liquid droplets that remain

suspended in the atmosphere for a long time

Particles and aerosols reflect or scatter light in

different directions before it reaches Earth’s

surface

Volcanic Connection

Volcanoes emit sulfate aerosols that affect heat balance in two ways

1. Reflect and scatter solar energy before it reaches Earth’s surface

2. Increase the formation of clouds, which further reflect and scatter solar energy

Periodically eject large amounts of sulfur, ash, and other particles into the atmosphere which significantly cools the climate

Mt. Pinatubo in the

Philippines

Erupted June 15th, 1991 (my birthday…weird)

Second largest volcanic eruption of the century

Produced high-speed avalanches of hot ash and gas, giant mudflows, and a cloud of volcanic ash hundreds of miles across

Planet cooled 1 degree Celsius from ‘91-’92 as a result

Greenhouse Gases

Atmospheric gases that absorb much of the

long-wave radiation

Include water vapor, carbon dioxide,

chlorofluorocarbons, and nitrous oxide

Together with particles and aerosols, these

gases absorb and reflect radiation and therefore

affect the energy balance of the atmosphere

Greenhouse Effect

The atmosphere’s ability to absorb energy with

longer wavelengths and convert it to heat

Makes the atmosphere warmer than it would be

if the outgoing long-wave radiation passed

through the atmosphere in the same way as the

incoming short-wave radiation

Greenhouse Effect Cont’d

Natural phenomenon that warms the lower

atmosphere about 35 degrees Celsius

Without it, Earth’s average temperature would

be a chilly -15 degrees Celsius

Essential to life

Radiative Forcing

Measures the strength of the greenhouse effect

Measured in units of watts per square meter

Total amount of energy that is absorbed by the gases

that lie above a square meter of Earth’s surface,

from ground level to the top of the atmosphere

Types and quantities of gases and particles in the

atmosphere determine its radiative forcing

Chlorofluorocarbons aka

CFC’s

Most effective absorbers of long-wave radiation

Can absorb thousands of times more energy

than a molecule of carbon dioxide

Greenhouse Gas

Aside from water vapor, carbon dioxide is the most

abundant greenhouse gas in the atmosphere

A single molecule of CFC can absorb thousands

times more energy than a molecule of carbon dioxide

There are a million molecules of carbon dioxide for

every one molecule of CFC

Carbon dioxide absorbs more heat than CFCs and all

other greenhouse gases, except for water vapor

Residence Time

The time that the average molecule spends in the atmosphere

Residence time for most greenhouse gases is decades or longer

The concentration of greenhouse gases is relatively well mixed throughout the entire atmosphere

Carbon dioxide is about the same everywhere within a given layer of the atmosphere

Concentration of Greenhouse

Gases

Atmospheric concentrations of greenhouse gases are increasing steadily

CO2 increased from 316 ppm in 1958 to 375 ppm in 2005

Atmospheric carbon has been increasing since long before the 1950s

Ice core dating allows air that was trapped when ice was formed to be tested for composition

Why the increase? Human activities have disrupted global biogeochemical cycles of carbon, nitrogen, and sulfur

Create entirely new flows and accelerate existing flows increase the amount of carbon stored in the atmosphere as carbon dioxide and methane

Carbon Storage Great quantities are stored in Earth’s crust as fossil

fuels coal, oil, natural gas, oil shale, and tar sands

Carbon remains of plants and microscopic organisms

that accumulated in the crust over millions of years

Accumulation partially reversed by the Industrial

Revolution burning of fuels releases excess carbon

into the atmosphere when it should be in a storage

Fossil Fuels Most carbon is returned to the atmosphere in the form of carbon dioxide (byproduct of combustion)

Some is returned as methane coal mines

Methane can suffocate miners and cause explosions

Burning coal emits sulfur back into the atmosphere

Land Use Change

The general process by which humans change the amount of carbon stored in terrestrial biota

Replaces natural ecosystems with others that meet human needs and wants

Often stores less carbon than their natural predecessors in the plants

Agriculture, forest fires, etc. release carbon into the atmosphere

Detecting Climate Change

Detection seeks to determine whether or not

the climate is actually changing

Consists of three steps:

1. Scientists choose an indicator that

represents some aspect of Earth’s climate

2. They measure its mean and natural variability

3. Determine whether recent changes are

greater than expected based on natural

variability

Indicators of Climate

Change

Global increase in sea levels warm water is

less dense and expands causing higher levels

Response of biological systems to changes in

climate

Species moving their habitats

Satellite measurements of vegetation

Attributing Change to Human

Activity Attribution: the process of

establishing a cause and effect

relationship between human activity

and the observed change in climate

Intergovernmental Panel on Climate

Change states that the balance of

evidence suggests that there is a

discernable human influence on

climate

Two Methodologies

1. Statistical analysis of historical data and

computer models of the climate system

2. Climate models

Skepticism

1. Reluctance to slow emissions

2. Incomplete understanding of science and the data

presented

Some aerosols block out incoming infrared rays and

therefore cause a cooling of temps

3. Supposed mismatch between the rise in surface

temperatures as measured by satellites and

thermometers on the ground

Satellites measure temps in all atmospheric layers

What does the Future

Hold?

Strong correlation between Earth’s temperature

and the atmospheric concentration of green

house gases over the last 420,000 years

Effects of Warmer Temps Permafrost stores methane that is released

if/when it melts

Higher temps increase the speed of decay of

organic material which increases the flow of

carbon from soils to the atmosphere

Negative relationship between temperature

and he solubility of carbon dioxide in water,

so rising temps could increase the flow of

carbon dioxide from the ocean to the

atmosphere

Computers

Future concentrations are simulated using

different scenarios for emissions

Allow us to evaluate how climate will change if

population grows more slowly than anticipated,

if people become richer than anticipated, or if

society develops and adapts energy-efficient

technologies

Impact of Climate Change Animal behavior possible

extinction of species, change in

migration patterns, etc.

Food Supply increase is some

areas and decrease in others due to

shifting temperatures

Rising sea levels destroy homes,

factories, bridges, some entire cities

What Can We Do?

Stabilize the amount of greenhouse

gases in the atmosphere at a level that

would prevent dangerous interference

with the climate system

Allow ecosystems to adapt naturally to

climate change to ensure that food

production isn’t threatened

Four Categories

1. Reductions in emissions of greenhouse gases

2. Research and development for new supply and

conservation technologies that lower the cost

of reducing greenhouse gas emissions

Four Categories

3. Research to reduce critical areas of uncertainty

4. Investment in actions that help human and

natural systems adapt to climate change

Clean Development

Mechanism Scheme developed by the United Nations

Allows nations to earn credit for reducing emissions in another nation

Ex.) Agreement b/t Chile’s largest pork producer and power companies in Japan and Canada

Power companies purchased the right to emit more CO2 when they bought the pig farmers equipment to capture methane and burn it as a renewable source of energy

Kyoto Protocol

Effective as of February 2005

Industrialized nations are obligated to reduce

their CO2 emissions below 1990 levels by 2008-

2012

Efficiency standards

Taxes on CO2 emissions

Trading schemes among nations

Kyoto Protocol: US & AUS US and Australia are not part of the Kyoto

Protocol

Bush withdrew when he took office in 2001

saying that reducing CO2 emissions would hurt

US economy