The sun sends out energy as heat and light. This energy comes to our earth during the day time.

Some of the sun’s rays get ‘trapped’ in the atmosphere.

Some of them get reflected back into space.

The ones which get through the atmosphere warm the earth up.

All the time, the earth radiates heat into space, which cools it down. We only really notice this at night, when there is no heating from the sun.

Some of the heat going out is trapped by the atmosphere. This is what makes our planet warm enough to live on.

But if too much heat is trapped, our planet will warm up and the climate will change.

What is the atmosphere and why does it trap heat?

The atmosphere is the air around the surface of the earth. It is made from a mixture of gases. We need it for animals and plants to survive.

Some of the gases act like a blanket, trapping heat. These gases are called ‘greenhouse gases’.

This is known as the ‘Natural Greenhouse Effect’. Without it, the earth would be much colder.

(the atmosphere is really much thinner than it looks above)

So why is global warming happening?

(the atmosphere is really much thinner than it looks above)

The heating of the earth through human activities is called the ‘Enhanced Greenhouse Effect’ and this is causing the earth to heat up, or global warming.

Global warming doesn’t just mean that the earth gets hotter, it means that the whole climate is changing.

Which gases in the atmosphere trap heat?The atmosphere is made of 78% Nitrogen and 21% Oxygen.But these gases don’t trap heat and cause global warming or climate change.What % of the atmosphere is left?

The gases which trap heat make up less than 1% of the atmosphere! They are called the ‘greenhouse gases’.

The main greenhouse gases are:Carbon dioxide Methane Nitrous oxide Ozone Water vapour Halocarbons

Human activity increases the amount of these gases in the atmosphere

Carbon dioxide ◦ combustion of solid waste, fossil fuels (oil, natural gas, and

coal), and wood and wood products Methane :

◦ production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock.

Nitrous oxide ◦ agricultural and industrial activities, as well as during

combustion of solid waste and fossil fuels. hydrofluorocarbons (HFCs), perfluorocarbons

(PFCs), and sulfur hexafluoride (SF6),◦ industrial processes.

How do humans increase carbon dioxide levels in the atmosphere?

Burning fossil fuels releases the carbon dioxide stored millions of years ago. Most of the increased carbon dioxide comes from fossil fuels

Deforestation releases the carbon stored in trees. Less trees also means less carbon dioxide can be removed from the atmosphere.

How do humans increase methane levels in the atmosphere?

The amount of methane in the atmosphere has increased by two and a half times since the Industrial Revolution.

Increased rubbish in landfill

Increased livestock farming

Methane is also released when fossil fuels are extracted

Methane is produced when bacteria rot organic matter

Power Plants 40% of carbon dioxide emissions stem from the burning of fossil fuels for the purpose of electricity generation

Cars 20% of carbon dioxide emissions comes from the burning of gasoline in internal-combustion engines of cars and light trucks with poor gas mileage contribute the most to global warming

Trucks Another 13% of carbon dioxide emissions come fromtrucks used mostly for commercial purposes

Airplanes Aviation causes 3.5 percent of global warming, and the figure could rise to 15 percent by 2050

Carbon Dioxide from Buildings Buildings structure account for about 12% of carbon dioxide emissions

Greenhouse Gas Emissions

Methane

• Derived from sources such as rice paddies, bovine flatulence, bacteria in bogs and fossil fuel production• In flooded fields, anaerobic conditions develop and the organic matter in the soil decomposes

Nitrous oxide • Naturally produced by oceans and rainforests• Man-made sources-nylon and nitric acid production, the use of fertilizers in agriculture, cars with catalytic converters and the burning of organic matter

Deforestation• Responsible for 25% of all carbon emissions entering the atmosphere by the burning and cutting of about 34 million

acres of trees each year

Health Water resources Polar regions Mountains Forests Deserts Coastal Zones Agriculture International

Effects of Global Warming

Negative EffectsRising Sea LevelChange of precipitation and local climate conditions; acid rainAlteration of forests and crop yieldsExpansions of deserts into existing rangelandsMore intense rainstormsDestabilization of Ocean currents

Positive EffectsCan stimulate plant growth in places where CO2 and temperature are the limiting factors (preventing photorespiration which can destroy existing sugars)Melting Arctic ice may open the Northwest Passage in summer, which would cut 5,000 nautical miles from shipping routes between Europe and Asia

The effects are difficult to measure, but potentially dramatic.

Many species inhabit precisely bounded ecological niches, and so small changes in climate can cause disruptions in habitat or food availability.

Loss of key predator or prey species affects the life cycles of other organisms in the food chain.

Associated Climate Changes

• Global sea-level has increased 1-2 mm/yr; in 100 years a rise in sea level between 3.5 and 34.6 in. (9-88 cm) is expected

• Duration of ice cover of rivers and lakes decreased by 2 weeks in N. Hemisphere

• Arctic ice has thinned substantially, decreased in extent by 10-15%

Reduced permafrost in polar, sub-polar, mountainous regions

Growing season lengthened by 1-4 days in N. Hemisphere

Retreat of continental glaciers on all continents

Snow cover decreased by 10% (reduced solar reflection)

Source: Intergovernmental Panel on Climate Change, 2001 Report

The growth of crops depends on many factors, including temperature, precipitation, soil fertility, and surrounding land uses.

Extreme weather events (drought, hurricanes, floods, etc.) are very damaging to crops. The effects of more gradual affects (e.g., average temperature increase) are difficult to predict.

Developing countries will be much harder hit than developed countries, due to limited agricultural flexibility.

There are two basic adjustments: ● Work to mitigate the situation (reduce its

severity) by reducing emissions of greenhouse gases