- Dissertations, fiches de lectures, exemples du BAC

Le réchauffement climatique (document en anglais)

Compte Rendu : Le réchauffement climatique (document en anglais). Recherche parmi 291 000+ dissertations

Par   •  8 Décembre 2011  •  1 677 Mots (7 Pages)  •  1 392 Vues

Page 1 sur 7


I. What evidence is there that the earth is actually warming up?

Evidence for warming up of our Earth includes observed increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising average sea level.

We will focus on the global average air temperatures from 1880 to 2000 and the Temperature anomalies

in January 2007

Global warming refers to the rising average temperature of Earth's atmosphere. In the last 100 years, Earth's average surface temperature has increased by about 0.8 °C (with about two thirds of it occurring over just the last three decades). Warming of the climate system is unequivocal, and more than 90% of scientists agree with it.

Climate proxies show that the temperature had been relatively stable over the one or two thousand years before 1850.

And since 1979, land temperatures have increased about twice time faster than ocean temperatures (0.25 °C for land temperature instead of 0.13 °C for ocean temperature)

In the first document we can see that the curve is increasing. In 120 years, the temperature has raised to nearly 0.8 ° C (values ​​mentioned earlier). And in the second document, we can see that land temperature was 0.85 °C warmer than the 20th century average for January, which was almost 12.0 °C (based on preliminary data). We can also observe that the most unusually warm conditions were in the Northern Hemisphere (Europa, Russia...). And the weirdest thing is that in the eastern part of hte US is warmer than usually whereas the western part is colder.

It is caused by increasing greenhouse gases produced by human activities (such as deforestation and burning fossil fuel). Climate model projections indicate that during the 21st century the global surface temperature is likely to rise a further 1.1 to 2.9 °C for their lowest emissions scenario and 2.4 to 6.4 °C for their highest.

We will focus on the global average ocean temperatures and the rising average sea level

The Average sea temperature is increasing, the first document represents the temperature rise of 100 meters of the ocean around Antarctica (the drawing shows the forecast for a few years, to the right. On the left is a simulation from the temperature of our days and the hottest time of the last air cooler). We can see that this warming is not homogeneous and that the weather will be warmer than today. The second one, is showing the increase of sea level from 1960 to 2000 (which increased by approximately 60 mml)

An increase in global temperature will cause sea levels rise. It will change the amount and pattern of precipitation. Warming is expected to be strongest in the Arctic and would be associated with the end of the glaciers...

We will focus on Alaska's tundra, which is a mountain range and the widespread melting of snow and ice

Alaska's tundra is drying up and few years ago there was an actual fire there. It's weird because the ground should always be frozen. More, this year Alaska has received the least amount of snow ever recorded and has received more rain (the land has to be warm to receive rain instead of snow.). But all the glaciers are in the same situation as, as Alaska, Greenland is drying up too.

To show that, here are two kinds of graph. One of them is showing the ice melting in the north of Canada (the parts surrounded by dotted lines represent the part of the glacier that lost the most snow. They used to be at the same "color" as Greenland on the map), and the second one is a graph which shows the extensive area covered by snow in Alaska, based on years from 1978 to 2008 (we can clearly see a decrease of 3.5 million square kilometers)

So if Alaska is warming up, then the whole world must be warming up. Because we all know it is impossible for temperatures in one part of the world to increase while temperatures in another part of the world are decreasing.

II. What might be causing any global warming? Explain the Green house effect.

Main causes of Global Warming :

Natural causes are causes that are created by nature. One natural cause is a release of methane gas from arctic tundra and wetlands. Methane is a greenhouse gas and a very dangerous gas to our environment.

Man-made causes probably do the most damage to our planet. There are many man-made causes of global warming.

Pollution is one of the biggest man-made problems. Pollution comes in many shapes and sizes. Burning fossil fuels is one thing that causes pollution. Fossil fuels are fuels made of organic matter such as coal, or oil. When fossil fuels are burnt they give off a greenhouse gas called CO2.

Another major man-made cause of Global Warming is population. More people means more food, and more methods of transportation. That means more methane and more CO2 (because there will be more burning of fossil


Télécharger au format  txt (10 Kb)   pdf (124.8 Kb)   docx (12.1 Kb)  
Voir 6 pages de plus »
Uniquement disponible sur