Understanding the greenhouse effect and global warming
“Greenhouse gases” are one of the central concerns of COP 21, whose stated objective is to limit global warming to 1.5 °. The fight against the reduction of greenhouse gas emissions is not in itself new, officially started at the international level for 20 years with the Kyoto Protocol. But what does this famous protocol contain, what exactly does this symbolic figure of 1.5 ° mean, and what do “greenhouse gases” really mean?
A natural phenomenon
Due to the increasingly media coverage of global warming, the expression "greenhouse effect" now seems to be one of the black spots threatening the future of the planet. However, this is at the origin of a completely natural phenomenon, and essential for climate regulation. As the name suggests, this effect acts like a greenhouse by erecting a protective barrier around the planet. To put it simply, the greenhouse effect allows most of the solar rays to cross it towards the Earth, but partially retains and reflects the thermal radiation ("infrared"), re-emitted by the latter. This natural protection ensures an ideal temperature and prevents the Earth from suffering an average temperature of -50 °. Ozone, carbon dioxide, water vapor, methane and nitrous oxide are the main gases participating in this greenhouse effect, the famous “greenhouse gases”.
Greenhouse gases in global warming
Since the 19th century, and especially since the second half of the 20th century, the greenhouse is growing rapidly. Greenhouse gas emissions have increased sharply, especially those of carbon dioxide (CO2), powerfully amplifying the natural heat conservation mechanism, with a significant rise in temperatures as a result.
The cause of this phenomenon remains debated, even if the human responsibility is undeniable in part, and perhaps in its entirety. This warming indeed coincides with the beginnings of the industrial revolution and above all with the increasingly intensive use of fossil fuels (gas, oil, coal) which generate greenhouse gases.
So, whatever the real origins of this disturbing phenomenon, the result is there and admitted by all: the planet is heating up. Since its observed start, global warming has already reached 1.3 ° on average, and could exceed 3 ° in 2050. Even if these figures seem limited, in fact a warming exceeding 2 ° would already have major consequences in the region. human scale with catastrophic climatic upheavals.
Save the future of humanity
In order to contain the threat of global warming as well as possible, 184 member countries of the United Nations agreed in 1995 to reduce greenhouse gas emissions. This famous “Kyoto protocol”, which entered into force in 2005, provided for by 2012 to reduce total emissions by at least 5% compared to 1990. Some countries have reached their objectives (France, Great Britain) , others not (Japan, Canada, Spain); the United States, the second most greenhouse gas emitting country in the world, had not ratified the treaty.
The many other international meetings organized after Kyoto have tried to continue and intensify the effort, such as the Copenhagen conference in 2009, without much success. The COP 21 in Paris now intends to set a much more precise and strict objective: to limit global warming to 1.5 °. This threshold is considered to be the maximum to curb the atmospheric consequences of global warming, which beyond that could prove out of all control.
This objective, judged by some as particularly optimistic, is necessarily based on the elimination or the sharp decline in the use of fossil fuels, which pollute extremely well, and their replacement by renewable energies. He also assumes that global warming will stop growing on its own, which again leaves part of the international community skeptical.
However, it is essentially the future of humanity that is at stake in the long term, and even in the medium term. The Earth, for its part, is far from being at its first climatic phenomenon, alternating since its origins with numerous ice ages and warming. The last glaciation ended 10,000 years earlier, with a warming of 4 ° ... and a rise in sea level of 130 meters.