How global climate has really changed since scientists first alerted 30 years ago

How global climate has really changed since scientists first alerted 30 years ago

“Emissions from human activities significantly increase the concentrations of greenhouse gases in the atmosphere.” This sentence is taken from First report from IPCC* (gsoup intergovernmental experts on climate change)1990 date. Since then, this organization launched by United nations To assess scientific information on global warming, its risks, and the role of human activity, four other reports have been published. Monday, August 9, is the first part of its sixth report, expected in the fall of 2022, to be published. It should, once again, make the case for those calling for faster action against climate change. Because the latter has It has already started to a large extent and the climate is not like 30 years ago. Franceinfo It offers you to visualize this evolution in graphs.

More carbon dioxide emissions than ever

The main cause of global warming, human greenhouse gas emissions narrow It has not decreased since 1990. On the contrary: the annual production of carbon dioxide has jumped 63%, now reaching more than 36 gigatons, According to the World Bank. This increase has been slightly slower since 2010 than the previous decade. But, to limit warming to the recommended minimum of +1.5°C compared to the pre-industrial period, experts who gathered in 2015 at COP21 estimated that humanity could not exceed 580 gigatonnes of emissions. This means that 25% of this theoretical volume was released… in just four years.

With this production, the planet cannot fully absorb this carbon dioxide. Therefore, its concentration increases rapidly in the atmosphere. In 30 years, that level rose from 355 ppm to 412, an increase of 16%, to me’US Oceanic and Atmospheric Monitoring Agency (NOAA)*. As for the carbon dioxide absorbed by the planet, the phenomenon is not without consequences: “The oceans absorb a quarter of the emissions, which makes them acidic. This acidification has direct effects on animals, such as bleaching coral or weakening animals that have been exposed to scales.” Joël Guiot, Research Director at the European Center for Research and Education in Environmental Geosciences confirms.

Previously +1 degrees Celsius Globally

This is undoubtedly the most scrutinized indicator: High temperatures. On the graph, the red curve represents the difference by year, and the black curve represents a smooth average which makes it possible to see the evolution more clearly. According to data from NASA* compared to the period 1950-1980The rise in global temperatures has already arrived +1 degrees Celsius Joël Guiot points out the subtle contrasts of this average, emphasizing that “aAt high altitudes, the warming has already begun +3 degrees Celsius. Over the past ten years, the total increase has been +0.35 °C. This means that at the current rate, the +1.5°C critical limit, which would reduce the risks and consequences of global warming, will be exceeded as early as 2035.

Snow melt that has accelerated since 2007

The effects of climate change are also seen in the presence of ice on the Earth’s surface. This graph represents the minimum annual frozen area in the Northern Hemisphere, National Snow and Snow Data Center*. Interesting note: the 14 The lowest recorded since the early 1980s corresponds to the last 14 years. In 2020, the frozen surface of the northern hemisphere has fallen below 4 million square kilometers; In the 1990s, this minimum annual area averaged 6.4 million square kilometers. “This acceleration in ice melt is the result of a vicious cycle: Higher temperatures lead to melting of ice, and since ice usually reflects sunlight, its disappearance leads to greater absorption of this solar heat, and thus higher temperatures., details of Joël Guiot.

sea ​​level rise 9 cm in 30 years

Another consequence of melting ice: Sea level rise. Here again, this increase, which reaches about 9 cm in 30 years, is very pronounced and persistent, NOAA Reports*. If that height of a few centimeters might seem insignificant, Joel Joyot explains it “During storms or the phenomenon of sea inundation, these centimeters are enough to allow water to advance further inland. In France, a region like the Camargue is particularly sensitive to this increase.”

* The links followed by an asterisk are written in English.

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