Global Warming

DEFINITION Global warming refers to the gradual

temperature increase on earth. As the planet is progressively heating, climate

patterns tend to change drastically, with more and more violent and unpredictable weather phenomena affecting the globe. Progressive areas are rapidly being reduced to deserts, others to icy lands, making human life almost impossible.

The Earth’s atmosphere

EARTH

TROPOSPHERE: it is the densest layer which contains oxygen,nitrogen,carbon dioxide, water vapour and methane.

STRATOSPHERE: in this part of the air surrounding the Earth there is an ozone layer.

MESOSPHERE

THERMOSPHERE

EXOSPHERE

GLOBAL WARMING AND GREENHOUSE EFFECT

Above the Earth’s surface there is a layer of gases, like carbon

dioxide (CO2) and methane (CH4), which have the effect of cushioning it. The radiation from the sun is both absorbed in the atmosphere and in the Earth’s surface. The infrared radiation becomes a problem when the layer of the gases gets too thick. When this happens, the radiations which come from the earth cannot escape in the atmosphere and are absorbed in it, causing excessive heat, which determines global warming. Besides this the absorption of the solar rays which makes our planet warm generates a natural phenomenon interrelated to global warming, called “Greenhouse effect”, which consists in the solar energy gases entrapment, which makes life possible on our planet.

INFRARED RADIATION

Infrared radiation is just as important to the Earth’s weather and climate as sunlight is. This is because, for all the sunlight that the Earth absorbs, an equal amount of IR must travel from the Earth back into space. If this was not the case, there would be global warming or global cooling. Everything emits infrared radiation but we usually do not notice it because it is often weak.

THE GREENHOUSE EFFECT DISPLAYED

THE GREENHOUSE EFFECT When the sunrays travel and reach the atmosphere,

which is made of several gases, the planet’s surface (land, water and biosphere), absorbs the solar energy. Gases like water vapour, carbon dioxide, nitrous oxide, methane and ozone trap the energy from the sun and prevent the heat from escaping back into the space. Though only a limited part of the energy passes back into space, but most of it remains in the atmosphere, the Earth heats up. These gases are known as greenhouse gases and the natural process of keeping the Earth’s temperature warm and constant is known as “greenhouse effect”.

GLOBAL WARMING: CAUSES

NATURAL CAUSES• Changes in solar radiation• Volcanic dust• Natural greenhouse gases (GHG)

HUMAN CAUSES• Increase in greenhouse gases• Burning fossil fuels (coal,oil,

natural gases) • Land use: urbanization and

deforestation• Pollution (due to the use of

aereosols,spray cans,fridges that produce chluorofluorocarbons)

• Breeding of vast numbers of methane-producing livestock, such as cows.

IMPACT OF THE GREENHOUSE EFFECTWe know that the planet warmed up on an average of

1°C in the past century…

A RISE OF JUST 2°C WOULD INEVITABLY MEAN:

Severe storms and floods in some countries and droughts in many others;

Increased rate of acidity in seas, with definite extinction of coral and krill, food chain destruction;

No Artic ice in summer ; Ice melting and submersion of more and more lands.As the Earth warms, the impact can fuel and accelerate these events.

BEYOND 2°C

Scientists predict possible rises up to 6° this century: if we do not drastically cut greenhouse gas emissions, it will be a disaster for all humans and the planet, too.

If this happens:Rainforest will die;The ancient ice sheets will melt;Sea levels will dramatically rise.

A GLOBAL CLIMATE DEAL

We urgently need to set strict and binding emissions targets on the developed industrial nations.

We need to cut GHG emissions at least 40% by 2020, and at least 80% by 2050.

CARBON DIOXIDECarbon dioxide is a natural gas, essential forlife on Earth. It is absorbed by plants as theygrow and emitted by vegetable and animal life

forms (or produced when fossil fuels are burnt such as carbon, oil). It is the

most common ‘greenhouse gas’.

METHANE Methane is the major component of natural gas

and it is found underground. Methane is a powerful trapping agent, and contributes to global warming by holding infrared radiation near the Earth’s surface. Its chemical formula is CH4, being made of one atom of carbon and four of hydrogen.

HYDROGEN

CARBON

Methane sourcesThe main methane emission sources in the atmosphere are:• household waste decay in dumps,• natural sources (bogs): 23%,• extraction from fossil fuels: 20%,• livestock digestion process: 17%,• bacteria found in rice fields: 12%,• heating or anaerobic digestion of biomasses.The 60-80% of world emissions comes out from human activities: coalmines, dumps, oil activities, pipelines and agriculture. Besides this, large quantities of methane in the form of methane clatrates are estimated to be found in ocean depths.

SULFUR HEXAFLUORIDE Sulfur hexafluoride is one of the most

powerful greenhouse gases. It is due to the industrial processes of the electronic industry. Sulfur hexafluoride is very strong and the industry has taken various steps to limit its release.

WATER VAPOUR Water vapour exists naturally in the atmosphere,

because water evaporates from the oceans, forms clouds, and clouds cause precipitations. When vapour concentrates in the atmosphere, it traps infrared radiation, and becomes a dangerous greenhouse gas.

CHLOROFLUOROCARBONS Aerosols, hairspray cans, fridges, plastics,

etc. produce a group of highly dangerous greenhouse gases called chlorofluorocarbons that cause a hole in the ozone layer.

THE OZONE LAYER

Ozone is a form of oxigen that is made of three atoms instead of two. Most of the ozone in the atmosphere is in a layer concentrated around two miles above the Earth’s surface. The ozone layer absorbs ultra-violet radiation which is very dangerous for us and our planet.

THE HOLE IN THE OZONE LAYER

The hole in the ozone layer is caused by greenhouse gases like CFC. People often confuse global warming with the hole in the ozone layer but these two phenomena though correlated are slightly different.

HUMAN ACTIVITY Human beings are contributing to increase

greenhouse gases levels through the burning of fossil fuels, the cutting and burning of forests, through smog emissions and chemical processes.

Liceo Scientifico Statale«G. Galilei»

PescaraA. S. 2012-2013

UDA: Global Warming

made by: MARCO DI NARDO

AND LUCA CICCONETTI

Classe 2^A

English Teacher: Prof.ssa Miscia Roberta