May 29, 2024

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How the global climate has already changed since scientists first warned 30 years ago

“Emissions from human activities dramatically increase atmospheric concentrations of greenhouse gases.” This sentence, taken from it First report IPCC* (G.Wrap Intergovernmental Experts on Climate Change), Date 1990. Since then, the organization has been launched United Nations Four more reports have been published to evaluate scientific information on global warming, its risks and the role of human activity. On Monday, August 9, the first part of its sixth report, expected in the fall of 2022, was released. This, again, should give arguments to those who call for quick action against climate change. Because the latter is It has already begun greatly and the climate is not 30 years old. Francinepo It allows you to visualize this evolution in maps.

Ever-increasing carbon dioxide emissions

The primary cause of global warming is human greenhouse gas emissions Tightness Did not decrease after 1990. It is the opposite: annual CO2 production has increased 63%, Now more than 36 gigatons, According to the World Bank. This increase has been slightly slower since 2010 than in the previous decade. However, experts at COP21 in 2015 estimated that humanity could not exceed 580 gigatons of emissions, limiting global warming to the recommended +1.5 ° C range compared to pre-industrial times. This means that 25% of this theoretical volume was awarded … in just four years.

With such production, this CO2 cannot be fully absorbed by the planet. Therefore its concentration increases rapidly in the atmosphere. In 30 years, this level has increased from 355 parts per million to 412, an increase of 16%, Step ‘American Institute for Ocean and Atmospheric Surveillance (NOAA)*. With regard to the CO2 absorbed by the planet, this phenomenon is not without consequences: “A quarter of the emissions are absorbed by the oceans, which acidifies them. This acidification has direct effects on animals, such as coral bleaching or weakening of shelled animals. “ Joel Kyot, director of research at the European Center for Research and Education in Environmental Geography, emphasizes.

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Already +1 C All over the world

This is undoubtedly the most studied indicator: Increasing temperature. On the map, the red curve represents the difference for the year and black is the smoothed average, which helps to see evolution more clearly. According to NASA data*, Compared to time 1950-1980Global warming has already reached +1 C And Joel Kyot points out the hidden inequalities of this mean, “aAt higher altitudes, warming will already be reached +3 C “. Over the past ten years, the overall increase has been + 0.35 C. This means that at the current rate, the critical bar of +1.5 ° C, which will reduce the risks and effects of global warming, will be overcome before 2035.

Melting ice has accelerated since 2007

The effects of climate change are seen in the presence of snow on the Earth’s surface. This map shows the least frozen area in the Northern Hemisphere per year, selon le National Snow and Ice Data Center*. Observation Surprising: The The 14 lowest levels recorded since the early 1980s are comparable to the last 14 years. By 2020, the frozen surface of the Northern Hemisphere will have fallen below 4 million square kilometers; In the 1990s, this minimum annual area averaged 6.4 million square kilometers. “This acceleration in the melting of ice is the result of a vicious circle: The rise in temperature melts the ice, and since the ice usually reflects the sun’s rays, its disappearance absorbs more of this solar heat, so the temperature rises., Details Joël Guiot.

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Sea level rise 9 cm In 30 years

Another effect of this melting ice: Rising sea level. Here again, this increase, in the order of about 9 cm in 30 years, is very clear and continuous, NOAA reports*. If this rise of a few centimeters seems too low, Joel Kyot explains it “During storms or sinking events, these centimeters are enough to allow water to still advance inland. In France, an area like Gamar is particularly sensitive to this increase. “

* Links following the star are in English.