Accelerating warming, intensifying the impacts causing unprecedented suffering to the humanity responsible for this devastation, and only one way to avoid the worst is to drastically reduce greenhouse gas emissions.
Here are the key conclusions of the sixth round of assessments by UN Climate Experts (IPCC), broken down into approximately 10,000 pages and three reports – climate physics, impacts and adaptation, emissions reduction solution – published in August 2021, February 2022 and this Monday, April 4. Like the previous evaluation cycles, which have taken place approximately every six to seven years since 1990, this trilogy will serve as a reference for the coming years.
No more doubts
Like it or not, the scientific evidence has dispelled any remaining doubts: Humans are “undeniably” responsible for global warming, which has increased by about +1.1°C since the pre-industrial era.
The rate at which the concentration of CO2 in the atmosphere increases between 1900 and 2019, largely related to fossil fuels, is at least ten times greater than at any other period in the past 800,000 years and the concentration of CO2 in the atmosphere has never been reached. been so high. so high for over 2 million years.
The 2015 Paris Agreement aims to limit warming to “well below” +2°C, if possible +1.5°C. But in all the scenarios the IPCC considers – from the most optimistic to the most pessimistic – global temperatures should reach +1.5°C or +1.6°C by 2030 compared to the pre-industrial era. That is ten years earlier than previously estimated.
Even if there is a possibility of falling back below the +1.5°C threshold by the end of the century, even a temporary exceedance would cause “irreversible” damage to certain fragile ecosystems (poles, mountains, coasts), with cascading effects on populations.
Even if current states’ commitments to cut emissions by 2030 were met, not exceeding +1.5°C would be at least temporarily “out of reach” and it would be difficult to reach +2°C . Without reinforcing current policies, warming could even reach 3.2°C by 2100, twice the ideal target of the Paris Agreement.
Avalanche of suffering
The devastating effects of climate change, long seen as a dash on the horizon, have become a reality in all four corners of the planet, with 3.3 to 3.6 billion people already “highly vulnerable”, or nearly half of the population. humanity. And that’s just the beginning.
Drought, heat waves with literally unbearable temperature extremes in places, storms, floods, water shortages, loss of agricultural crops… The secondary effects of warming of the atmosphere and oceans will increase, with a disproportionate impact on the most vulnerable, such as the poor and indigenous peoples.
Not forgetting the potential exodus of hundreds of millions of people who are facing the inexorable rise in sea levels, mainly due to the melting of the Greenland and Antarctic ice sheets.
Even if warming is limited to +2°C, the oceans could increase by about 50 cm in the 21st century and this increase could reach almost 2 meters by 2300, or twice as much as estimated by the IPCC in 2019.
The IPCC continues to reiterate that its role is not to make recommendations, but the scenarios it has drawn up leave no choice if humanity is to ensure a “liveable future” on the planet: even for a limit of 2°C, we have ” a rapid, radical and usually immediate reduction of greenhouse gas emissions in all sectors,” emphasizes the IPCC, with a focus on energy, transport, industry, agriculture and cities.
Limiting global warming to +1.5°C would thus require a major transformation of the energy system, increasing the use (without carbon capture technology) of coal, oil and gas by approximately 100%, 60% and 70% respectively. 2050 compared to 2019.
These three IPCC reports have never made room for the possibility of tipping points, abrupt changes in the climate system with “low probability” but “significant effects” that “cannot be ruled out”.
Among them, the point of no return leading to the total collapse of the ice sheets, able to raise the sea by tens of meters; thawing permafrost containing huge amounts of carbon; or even its transformation into Amazonian savanna, which absorbs an essential part of the CO2 emitted by human activities.
If scientists are currently unsure of the warming threshold that would trigger these “singular planetary-scale events”, they know that the risk is greater at +2°C than at +1.5°C. And that at +2.5 we °C go into a “very high risk”.