The Greenhouse effectThe Greenhouse effect

Is a natural process necessary for Is a natural process necessary for sustaining life on earthsustaining life on earth

Is produced by the sunIs produced by the sun’’s energy and s energy and earthearth’’s atmospheres atmosphere

How it worksHow it worksEnergy in the form of solar radiation is Energy in the form of solar radiation is

emitted toward earth. emitted toward earth.

26% is reflected26% is reflected

19% absorbed19% absorbed

55% reaches earth55% reaches earth’’s surface. s surface.

4% of that is reflected to space and4% of that is reflected to space and

the remaining 51% is absorbed by earththe remaining 51% is absorbed by earth’’s surface and s surface and re-emitted as long wave infrared radiation.re-emitted as long wave infrared radiation.

Greenhouse gases trap this radiation, Greenhouse gases trap this radiation, warm the atmosphere and emits the heat warm the atmosphere and emits the heat back to earth where a cycle begins.back to earth where a cycle begins.

Main Greenhouse GasesMain Greenhouse Gases CO2 has had a 33% increase in concentration in last CO2 has had a 33% increase in concentration in last

200 years.200 years.

Comes from burning fossil fuels for industry, Comes from burning fossil fuels for industry, transportation, heat, cooking, and electricity generation.transportation, heat, cooking, and electricity generation.

Also released Also released from deforestationfrom deforestation

Methane has risen 151% since 1750. Methane has risen 151% since 1750.

Released by large herds of cattle, tapping Released by large herds of cattle, tapping into fossil fuel deposits, dumping organic into fossil fuel deposits, dumping organic matter into landfills, and crops such as matter into landfills, and crops such as rice.rice.

Humans are cause of half of methane Humans are cause of half of methane releasedreleased

Ozone serves a dual purpose.Ozone serves a dual purpose. In lower stratosphere it keeps earth cooler In lower stratosphere it keeps earth cooler

by absorbing radiation before it reaches by absorbing radiation before it reaches earth. earth.

In troposphere it is building up and then In troposphere it is building up and then trapping heat. It also causes health trapping heat. It also causes health problems.problems.

It has decreased in stratosphere because It has decreased in stratosphere because of CFCs but increased 36% in troposphere of CFCs but increased 36% in troposphere since 1750.since 1750.

Halocarbon gases are man made. Halocarbon gases are man made. They include chlorofluorocarbons (CFCs) They include chlorofluorocarbons (CFCs)

which deplete the ozone layer. which deplete the ozone layer. Emissions have almost stopped now due Emissions have almost stopped now due

to the Montreal Protocol.to the Montreal Protocol.

Montreal ProtocolMontreal Protocol

Was called in 1987 because of health Was called in 1987 because of health concerns and fears of global warming.concerns and fears of global warming.

Signed by 180 nations, demanded CFC Signed by 180 nations, demanded CFC production dropped by 50%. Several production dropped by 50%. Several amendments now have dropped it to 95%.amendments now have dropped it to 95%.

Future of the ClimateFuture of the Climate

Scientists all agree earthScientists all agree earth’’s climate is s climate is warming due to increased greenhouse gas warming due to increased greenhouse gas concentrations. They do not know how it concentrations. They do not know how it will continue, however.will continue, however.

Some believe it will all work itself out.Some believe it will all work itself out.World Health Organization says immediate World Health Organization says immediate

and long term health benefits will come and long term health benefits will come from reducing gas emissions.from reducing gas emissions.

Reducing Greenhouse GasesReducing Greenhouse Gases

We can build more efficient machines. We can build more efficient machines. Automobiles are highly inefficient and Automobiles are highly inefficient and transportation is second highest transportation is second highest contributor to gas emissions in U.S.contributor to gas emissions in U.S.

Planting trees. An average tree intakes 13 Planting trees. An average tree intakes 13 pounds of carbon and carbon dioxide a pounds of carbon and carbon dioxide a year and maintains it for the life of the tree.year and maintains it for the life of the tree.

So the greenhouse effect is necessary for So the greenhouse effect is necessary for maintaining life on earth. maintaining life on earth.

Our climate is changing and we do not Our climate is changing and we do not know how it will continue. know how it will continue.

Greenhouse gas concentrations are rising Greenhouse gas concentrations are rising and need to be slowed as much as and need to be slowed as much as possible.possible.

Estimates point to a 1-3 degrees Celsius Estimates point to a 1-3 degrees Celsius rise in earthrise in earth’’s average temperature over s average temperature over the next century. the next century.