Since 1990, the IPCC has been trying to make itself heard. Five reports, all composed of several working groups, have since been published. The UN experts have completed the sixth, unveiling separately, in August, February and then this Monday, April 4, the three components that make up this document.
A new cry of alarm to try to save the planet and limit global warming which risks having dramatic consequences, even untenable living conditions for humans. Concretely, humanity has “less than three years” to reverse the curve of greenhouse gas emissions, responsible for climate change, if it wants to maintain a livable world, they warn, once again.
The first group of experts who shared their conclusions last August issued an observation that can no longer be doubted: humans play a decisive role in the acceleration of climate change and have no other choice. to drastically reduce greenhouse gas emissions, to limit the damage.
According to their observations, the Earth has already gained +1.1°C compared to the pre-industrial era. But in all the scenarios considered – from the most optimistic to the most pessimistic – the global temperature should reach +1.5°C or +1.6°C compared to the pre-industrial era around 2030. That is ten years more sooner than the previous IPCC estimate, made three years ago. The level of CO2 concentration is currently at its highest for two million years.
Oceans, lands, atmosphere, the whole planet is warming… but some areas faster than others. In the Arctic, for example, where sea ice is at its lowest in a thousand years, the average temperature on the coldest days is expected to increase three times faster than global warming. And if sea levels rise everywhere, they could reach up to 20% above average on many coastlines.
But there is even worse. Abrupt changes to the climate system with “low probability” but “significant impact”, called “breaking point” when they become irreversible, “cannot be excluded” according to the IPCC. It is “the starkest warning ever issued” about the role of human behavior in global warming, said COP26 President Alok Sharma.
- Irreversible effects
The second part of the sixth report by UN climate experts, published on February 28, 2022, paints a never-ending picture of the suffering endured by humanity hit by the impacts of global warming for which it is not sufficiently prepared. It is the synthesis of years of research on the effects of global warming and the way in which humans and living organisms can adapt to it.
Extreme heat, droughts, fires, cyclones, rising sea levels… “Human-induced climate change, including increased frequency and intensity of extreme events, has caused widespread negative impacts and losses and damages for nature and people, beyond the natural variability of the climate”, affirm from the outset the some 270 international scientists who contributed to the development of the UN report.
The devastating consequences of climate change, long seen as a dash on the horizon, have now become a reality across the planet, with 3.3 to 3.6 billion people already “very vulnerable”, nearly half of humanity. “The increase in meteorological and climatic extremes has led to irreversible impacts” on human societies and nature, concludes the IPCC. But this is only the beginning and the consequences on nature and man will increase: possible extinction of 3% to 14% of terrestrial species at +1.5°C, “billions” of additional people exposed to dengue fever, or in general, a “significant increase in illnesses and premature deaths”.
Regardless of the rate of greenhouse gas emissions, one billion people could live by 2050 in coastal areas at risk, as rising sea levels reinforce the effects of storms and sea flooding. The population at risk of sea flooding will double if the ocean rises 75 cm, a figure broadly consistent with projections for 2100. Today, around 900 million people live less than 10 m above sea level. above sea level. Anything over +1.5° would “lead to irreversible impacts” on vital ecosystems such as coral reefs, mountain glaciers and ice caps. “The risk of severe impacts increases with each additional fraction of warming,” temporary overshoot or not, the report said.
The new last and third installment, some 2,800 pages long, published on Monday, looks at solutions for reducing emissions responsible for global warming. To meet the objective of +2°C, it would be necessary, from 2030 to 2050, to reduce emissions each year as in 2020, an exceptional year when a good part of the world economy stopped due to Covid-19. In order not to exceed +2.5°C, emissions will have to peak in 2025, which seems unlikely, the trajectory having started to rise again from 2021, returning to record levels before the pandemic. However, at the level of emissions in 2019, the “carbon budget” available to maintain a 66% chance of remaining below +1.5°C would be completely consumed in eight years.
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Experts estimate that eliminating fossil fuel subsidies could reduce emissions by 10%. Maintaining +2°C implies that 30% of oil reserves, 50% of those of gas and 80% of those of coal are not used, unless techniques for capturing and storing the CO2 emitted are developed.
To meet the objectives of the Paris Agreement, the world must achieve “carbon neutrality” on all fronts by 2050, focusing on low-carbon or neutral sources, such as renewables and low-carbon energies – whose nuclear and hydroelectricity – which account for 37% of the world’s electricity production, the rest coming from fossil fuels. But the switch to less carbon-intensive energy should not push structural transformations into the background – soft mobility, electric vehicles, telecommuting, building insulation, fewer plane flights – which would make it possible to reduce emissions by 40% to 70% by 2050.
The group of experts also points to the responsibility of methane, a greenhouse gas with a much shorter lifespan than CO2 but 21 times more powerful, which contributes about a fifth of global warming. Meeting the Paris Agreement thus implies halving methane emissions by 2050 (compared to 2019 levels).
Even in the best scenarios, the reduction in emissions will have to be accompanied by the implementation of techniques for the elimination of carbon dioxide (EDC), or “negative emissions”, to achieve carbon neutrality. Possibilities range from natural CO2 capture, for example by planting trees, to extracting CO2 from the atmosphere, a technology that is not yet developed.
To achieve a warming limited to +1.5°C, 2300 billion dollars of investment per year between 2023 and 2052, just for the electricity sector, will be necessary. The figure drops to 1,700 billion if we aim for +2°C. These estimates of (de)growth do not, however, take into account the foreseeable gains, consequences of the avoidance of climatic catastrophes, food crises or the collapse of ecosystems.
“The benefits of scenarios that limit warming to 2°C exceed the costs of mitigation measures (of emissions) over the entire 21st century,” the report points out. The only benefits in terms of public health from a reduction in air pollution – the cause of 7 million premature deaths per year worldwide – would, for example, be of the same order as the investments to achieve this objective.