Global Warming Today we all have heard about global warming, maybe on TV or from our parents. Perhaps you have wondered what it is, but even if you didn’t, we will tell you.

What is the greenhouse effect? Some gases in the atmosphere create the greenhouse effect, it means that they trap the heat radiated from the earth and prevent it's exit into the outer space, as glass traps heat in a greenhouse. This phenomenon, usually natural and beneficial (without the greenhouse effect the earth would be at least 15 degrees C colder), is increasing in importance due to the increase in concentration of these gases because of human activities.

- The main greenhouse gases are: carbon dioxide (CO 2 ), methane, fluorocarbons, nitrous oxide (NO 2 ), and also water vapor and ozone contribute to the greenhouse effect. - Now that you know the greenhouse effect, the question is why it has become so important?

Greenhouse’s effect evolution Since ancient times the mankind has exploited natural resources to produce food and useful items for him to live. But industrial revolution brought man to a higher level of productivity at the expense of our planet’s health. In recent decades the greenhouse effect has been intensified because of immission in the atmosphere of a series of gas (called "greenhouse gases") that resulted in an increase in the Earth's average temperature. The cause of these emissions is the unbridled industrialization, so countries which produce most greenhouse gas are also the most industrialized and developed countries, like United States and China.

Global warming’s causes One of the causes of greenhouse effect, in addition to emissions of the industries, is the ozone hole. The term "ozone hole" is the gradual decrease of the thickness of the layer of ozone in the atmosphere. Ozone is a gas that is located in the outside air (stratosphere) where it forms a layer of very low concentration, approximately twenty kilometers thick.

This layer helps to mitigate the intensity of solar ultraviolet rays of type B arriving on Earth and which are harmful to the health of human beings. When the ozone layer depletes it increases the intensity of solar radiation that affects the Earth and then, among other things, the effect of heating of the Earth itself.

Global warming’s consequences It is not disputed that the increase of the greenhouse effect is due to human activities, but there is still much discussion about its possible consequences. Studies argue that some may be:

- The average surface temperature has increased overall in the 20th century by about 0.6 ° C. It’s very likely that year 1990 was the warmest of the century and 1998 the warmest year since instrumental records have (since 1861). - Data from satellites show a decrease of about 10% of snow cover from the late sixties. In particular, quickly equatorial snows and glaciers are withdrawing, on the Peruvian Andes and in Africa (33% of the Kilimanjaro ice has disappeared in the last 20 years), Artic sea ice is decreasing in late summer.

-I-In Antarctica, a warming of the entire continent isn't evident. But in West Antarctica, particularly the Antarctic Peninsula (south of Latin America), there are often massive collapse of large areas of ice forming icebergs. - Sea levels are rising because of water’s thermal expansion and glacier’s retreat: the increase during the 20th century was cm.

IPCC’s projections, performed with much better methods than in the past, show strong increases in the concentration of CO 2 in the atmosphere due to human activities, with significant consequences for the climate: - Increase in global average surface temperature 1.4 to 5.8 ° C over the period : the heating rate should increase compared the 20th century. The heating should be more pronounced in some areas of the planet (the northern part of North America, Northen and Central Asia).

-M-More intense water Evaporation, with more energy in the atmosphere: storms, tornadoes, more violent and frequent hurricanes. - The rise of sea level will continue: with consequences like erosions of sandy beaches and flooding of populated coastal areas (Nile’s delta, Bangladesh) and small islands (in particular, have threatned the atolls of the South Pacific).

Easier-transmission of some infectious diseases, including malaria and yellow fever. Some of these consequences have lasting effects on the climate.

Role of global warming in climate change Climate is characterized by 2 main factors: Cyclicity (daily cycles, seasonal, annual, decadal, millennial,...) mainly due to the Earth's movements (rotation, revolution, the inclination of the effect), or other cyclical causes (solar phases, sunspots,...); The variability in the cycles due to not cyclical causes primarily internal to the planet (movements of air masses, volcanic eruptions, ocean currents,...) but also external (meteorites, interaction with other stars or planets,...).

In this context, the greenhouse effect is a phenomenon which governs the relationship between cyclical variability and climate, making the climate system, an active system and self retroactive: in fact changing of the climate parameters (insolation, humidity...), the greenhouse effect reacts so as to return into regular and constant conditions the total energy of the Earth system. More particularly greenhouse effect means all of those phenomena by which nature intervenes to regulate the atmosphere's ability to retain or leave energy coming from the sun.

How to combat the greenhouse effect Unfortunately, greenhouse effect is an extremely complex phenomenon still subject to large studies. Therefore, there are many theories and interpretations (ranging from large alarmist studies to others involving natural attenuation due to increased cloud cover generated by the greenhouse effect itself), however, generally the actions that are advocated by most scholars are:

-S-Saving energy use of energy from renewable sources (solar, wind, hydroelectric, geothermal, biomass) or from fossil fuels, preferably natural gas than oil or coal (burning methane produces less carbon dioxide being equal energy produced). -P-Phasing out of CFCs, reduction of other greenhouse gases -R-Reduction of deforestation - Some countries have signed the Kyoto Protocol

The Kyoto Protocol This is an international agreement signed in 1997 by 84 countries, identifying targets for the reduction of greenhouse gases. The Protocol has been ratified by 146 countries (but not the U.S.) and entered into force in January A decrease of 5% on average by 2012, compared to their emission levels of 1990, is set for developed countries. Since the current trend is to a significant increase in emissions, reduction of 5% would be a great result, but not enough to stop the rise in temperature.

The protocol provides three tools: - Emission trading: forests planted since 1990 are considered carbon deposits, and loans are approved replacing the cuts in emissions. They can also be recognized as a credit projects to harness renewable energy (solar, wind, biomass), or improvements of existing energy generation systems. The relatively developed countries can buy and sell emission permits, to redistribute the cheapest way between countries and between emissions agreed. The Scheme of Trade of the European Union's emissions is the largest multi-trade greenhouse gas emissions in the world. It has started in January 2005 and all 25 member states participate in it.

- Joint Implementation and Clean Development Mechanism: they allow to achieve the reduction of emissions in third countries, where abatement costs are lower.

Made from: Altavilla Grazia Maria Di Clemente Mariaelena Scarpulla Erminia Travaglia Silvia With the collaboration of: Sturnio Sarah Bannò Mariolina Parisi Marina Livera Serena Popolo Silvia Giangreco Alessia