« It has been clear for decades that Earth’s climate is changing, and the impact of human activities on the climate system is indisputable, » said Masson-Delmotte(a French paleoclimatologist. Research Director at the CEA and Co-Chair of IPCC Group No. 1).
The publication of the 6th IPCC report reflects, not surprisingly, the catastrophic scale and speed of current climate change. and it is again clear that climate change affects all regions of the world and affects all climate systems.
Given the inertia of our societies regarding the issue, which is crucial for the future of our civilization, our planet will continue to warm to far exceed the limits set by the Paris Agreement concluded in 2015, which planned to contain this warming below 2 C, or even 1.5 C compared to the pre-industrial era.
In order not to exceed these limits, States have committed to reducing their greenhouse gas emissions, even as the effects of climate change are increasingly present. But the Earth could make its own and thwart this project.
Melting permafrost appears to threaten these objectives.
This frozen subsoil, whose temperature does not exceed 0 degrees for two consecutive years in normal times, shows us how alarming the situation is. It ismade up of organic matter that has frozen before decomposition, and which due to the increase in temperature will decompose by releasing carbon in the form of greenhouse gases: carbon dioxide and methane.
However, given the extent of permafrost, which accounts for 1/4 of the soil area in the northern hemisphere, its melting would result in the release into the atmosphere of 1672 billion tons of carbon currently sequestered in the frozen subsoil.
Not to mention the very large quantities of mercury contained in the soils of the Arctic, which by spreading via marine currents or atmospheric exchangeshave contaminated all of our environments. A real poison for the living. The amounts of methane and CO₂ it traps correspond to about 15 years of human emissions.
To limit and stabilize global warming below 2°C, or even 1.5°C, the IPCC reaffirms thatCO2 emissions must be reduced rapidly and net-zero CO2 emissions must be achieved around 2050. « Limiting other greenhouse gases and air pollutants, especially methane, could benefit both public health and the climate, » the experts add in their report. They warn, however: « Human-induced warming and sea-level rise would continue for centuries due to time scales associated with climate processes and feedbacks, even if greenhouse gas concentrations were stabilized. »
In addition, permafrost could experience what scientists call a tipping point: beyond a certain rise in temperatures, it will continue to melt and release greenhouse gases into the atmosphere, regardless of the decrease in emissions.