When the earth is heated by the sun, it restores some of the rays it receives. Another part of the rays retransmitted by the ground in the form of infrared radiation is retained by the greenhouse gases (carbon dioxide, methane, etc.) and sent back to the Earth. These infrared rays help warm the Earth, which is normal.The climate naturally varies since the formation of the Earth. What is different today is the speed of this change. Through its activity, humans have disrupted this natural mechanism by producing more greenhouse gases. The burning of oil and gas, deforestation, intensive agriculture, etc. are the direct effects of the industrial revolution. Gases accumulate in the atmosphere at a level well above the natural level. The gases concerned are mainly carbon dioxide (it is present in quantity 1.5 times larger than in the 19th century) and methane.
A rise in temperatures: Earth's temperature has already increased by 0.8 ° C since the end of the 19th century and scorching episodes are more frequent and affect more territories than before. If the CO2 concentration doubles by 2100, the temperature of the Earth will have increased by 1.5 to 4.5 ° C.Ocean Elevation: As glaciers and polar ice caps melt and recede, ocean levels rise by about 3.3 mm per year, and this sea level rise is going up. increase. In the worst-case scenario, sea level could have risen by one meter in 2100. Entire territories are set to disappear like Kiribati or the Maldives.Increased precipitation in the northern hemisphere and droughts in the southern hemisphere and regions already prone to drought. Droughts will be longer and more frequent, and the flow of rivers will be reduced: biodiversity will be hit hard and humans will have trouble cooling thermal and nuclear power plants, which can lead to a significant decline in production of water. 'electricity.Ocean Acidification: Excess CO2 dissolves in surface water and makes it more acidic. The rapidity of the phenomenon prevents scientists from being able to predict its effects on living organisms: some shellfish and plankton, bases of the food chain, may not be able to adapt, and their disappearance could have an impact on the whole of the world. food chain, including on humans.In terms of climate change, there are strong regional disparities, but the trend is warming as shown in the map below. NASA and NOAA have concluded after studies that 2016 has been the hottest year on the planet since the beginning of the temperature surveys in 1880.
source: Serge Planton Meteofrance, extract from the IPCC 2015 report
We are not talking about climate change without talking about El Niño. Indeed, El Niño is an oceanic and atmospheric phenomenon that affects the global climate - tropical storms, rainfall - and can add to the effects of climate change. On the other hand, there is currently no consensus on the question of the impact of climate change on this phenomenon. This natural cyclical phenomenon, which returns every three to seven years, warms the waters of the equatorial Pacific, along the coasts of Ecuador and Peru, and inverts the Pacific trade winds. It causes major weather changes on a global scale.
But El Niño does not explain everything. The previous heat record of 2014, a year free of El Niño, is the proof.