Global warming

Climate: Earth, climatic conditions, science and society

Climate change is today a problem really important, and people become aware.

So we need to give information to people who don’t know exactly what is global warming.

We will firstly present the complexity of the climate change. Currently, the Earth become cooler because of the greenhouse gases but it has not always been the same.

Indeed, with the Milankovic’s researches, in the 20th century, we know that the climate has hot cycles, called interglacial era, and cold cycles, called ice age. This variation comes from different causes, it can be from the Earth position in the space, from naturals disasters like volcanos, the Sun, meteorites… But, this century a new variation appears. Indeed, with the industrial Revolution, the emission of carbon dioxide increases and we understand that this gas is a greenhouse gases. The greenhouse effect is a natural phenomena who trap heat just like the glass roof of a greenhouse, solar radiation reaches the Earth's atmosphere - some of this is reflected back into space, the rest of the sun's energy is absorbed by the land and the oceans, heating the Earth, heat radiates from Earth towards space and some of this heat is trapped by greenhouse gases in the atmosphere, keeping the Earth warm enough to sustain life. With this, the Earth can stay cool, the average temperature on the planet is about 14 degrees Celsius, without the greenhouse effect, our planet will be colder and live on will be complicate. This natural phenomenon is compensating by others naturals phenomena like photosynthesis (plants catch CO2 and release O2).

 This greenhouse effect gases are carbon dioxide, methane, nitrous oxide, and water vapor. But humans, with the industrial Revolution, use more and more of fossil fuels like fuel, gazes, coal, and when this hydrocarbon burn, and they release too much carbon dioxide, plants can’t no photosynthesis this and some of the gases stay on the atmosphere. Consequently the greenhouse effect increases and the Earth come hotter.

A close look at the economic activities that release greenhouse gases tells a rather complex story. In fact, we can see key activities responsible for the largest mass of emissions. By burning fossil fuels and changing the way we use land (like clearing forests to raise cattle), we release the carbon that was captured and kept out of the carbon cycle for hundreds to millions of years. For the last two centuries, fossil fuels like coal, oil and natural gas, provided the energy we needed for our homes and economy — industry, agriculture, transport and so on. And this fossil fuel, when they are released, emits carbon, who is one of the first greenhouse gases. We continue our research about this greenhouse effect and his causes, and the more we know the more complicated the situation becomes.

States search to reduce the carbon emission, but firstly, they need to know the source of this emission. We can see that the bigger source come from big economic sector, so reduce the use of hydrocarbon like fuel, gazes, coal… will reduce the carbon emission but will impact the economy too. So, the states can’t reduce the use of hydrocarbon because all the country’s economy will be touch.

The Earth’s atmospher :

The atmosphere is a gaseous layer that envelops the whole Earth. The majority of the air is composed of diazote (78%), dioxygen (21%) and other gases, including argon and carbon dioxide. These play a fundamental role in the maintenance of life: partial absorption of ultraviolet radiation, thermal buffer or warming of the surface by greenhouse effect and by partially reducing the temperature differences between day and night. The water vapor contained in the humid air represents on average 0, 25 % of the total mass of the atmosphere.

Water vapor has the particularity of being the only fluid in the Earth’s atmosphere that can change phase rapidly (ice, water, steam), essentially as a function of temperature. Heat tends to cause air and humidity to rise, while atmospheric pressure and temperature decrease with altitude. The gases of the atmosphere are constantly stirred; the atmosphere is not homogeneous, as much by its composition as by its physical characteristics. 

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Its limit is difficult to determine because there is no clearly defined border it consists of several layers:

There is no marked border between the atmosphere and space, as it becomes more and more delicate and gradually fades into space. However, from the observation of the variation of the density of the terrestrial gases, it can be established that the thickness of the terrestrial atmosphere varies between 350 and 800 km (depending on the solar activity), with an average thickness of about 600 km. This limit corresponds to the borders between thermosphere and exosphere.  

The concentration of minority components, and in particular pollutants, is very heterogeneous on the surface of the globe, because very local emission sources exist, either related to human activity (factories, indoor or outdoor air, etc.) or to natural processes (geothermal, decomposition of organic matter, etc.)

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