Science

Humanity on the cusp of cataclysmic climate fallout

Water shortage, exodus, malnutrition, extinction of species … Life on Earth as we know it will inevitably be transformed by climate change when children born in 2021 will be 30 years old, or even earlier, warns a project of report by UN climate experts obtained by AFP.

Whatever the rate of reduction in greenhouse gas emissions, the devastating impacts of global warming on nature and the humanity that depends on it will accelerate, assures the IPCC, and become painfully palpable well before 2050.

“Life on Earth can recover from major climate change by evolving into new species and creating new ecosystems,” notes the 137-page technical summary. “Humanity cannot”.

The draft report written by hundreds of scientists attached to the Intergovernmental Panel on Climate Change (IPCC), which is authoritative in the field, oscillates between an apocalyptic tone and the hope offered to men to change their destiny by immediate and drastic measures.

The comprehensive 4,000-page evaluation report, much more alarmist than the previous one in 2014, aims to inform political decisions.

Even if its main conclusions will not change, it will not be officially published until February 2022, after its approval by consensus by the 195 member states.

Too late, however, for the crucial international meetings on climate and biodiversity scheduled for the end of 2021, note some scientists.

Among its most important conclusions is a lowering of the threshold beyond which warming can be considered acceptable.

By signing the Paris Agreement in 2015, the world committed to limiting global warming to + 2 ° C compared to the pre-industrial era, if possible + 1.5 ° C.

From now on, the IPCC estimates that exceeding + 1.5 ° C could already lead “gradually, to serious consequences, for centuries, and sometimes irreversible”.

And according to the World Meteorological Organization, the probability that this threshold of + 1.5 ° C over one year will be exceeded by 2025 is already 40%.

– “Our children and grandchildren” –

“The worst is yet to come, with implications for the lives of our children and our grandchildren far more than ours”, insists the IPCC, while awareness of the climate crisis has never been so extensive .

The climate has already changed. While the rise in average temperatures since the middle of the 19th century has reached 1.1 ° C, the effects are already severe and will be increasingly violent, even if CO2 emissions are curbed.

And the living things – human or not – least to blame for these shows are, ironically, those who will suffer the most.

For some animals and plant varieties, it may even be too late: “Even at + 1.5 ° C, living conditions will change beyond the ability of certain organisms to adapt”, underlines the report, citing the coral reefs on which half a billion people depend.

Among the species on borrowed time are the animals of the Arctic, a territory that is warming three times faster than average. On the spot, ancestral ways of life, of people living in close connection with the ice could also disappear.

– Not ready –

Agriculture, breeding, fishing, aquaculture …. “In all food production systems, sudden losses increase”, also observes the report, pointing to climatic hazards as “the main driver”.

However, humanity is at this stage not armed to face the certain deterioration of the situation. “The current levels of adaptation will be insufficient to respond to future climate risks”, warns the IPCC.

Even limiting the increase to 2 ° C, up to 80 million more people will go hungry by 2050 and 130 million could fall into extreme poverty within ten years.

In 2050, hundreds of millions of inhabitants of coastal cities will be threatened by more frequent wave-submersion, caused by rising sea levels, which will in turn lead to significant migrations.

At + 1.5 ° C, in cities, 350 million additional inhabitants will be exposed to water shortages, 400 million at + 2 ° C. And with that extra half a degree, 420 million more people will be at risk from extreme heatwaves.

The risk of drought in the world (AFP – Gal ROMA)

“The costs of adaptation for Africa are expected to increase by tens of billions of dollars per year above + 2 ° C,” the report predicts. We still have to find this money.

The text also underlines the danger of cascading effects. Some regions (eastern Brazil, Southeast Asia, central China) and almost all coastal areas could be hit by three or four simultaneous weather disasters, or even more: heatwave, drought, cyclone, fires, floods, diseases carried by people. mosquitoes …

And we must also take into account the amplifying effects of other human activities harmful to the planet, notes the report: destruction of habitats, overexploitation of resources, pollution, spread of disease …

“The world faces complex intertwined challenges,” comments Nicholas Stern, a climate economist, not involved in this report. “Unless we face them at the same time, we will not meet any,” he said.

– Radical choices –

Without forgetting the uncertainties around the “tipping points”, key elements whose substantial modification could lead the climate system towards a violent and irremediable change.

Above + 2 ° C, the melting of the Greenland and West Antarctic ice caps (which contain enough water to cause the sea level to rise by 13 meters) could for example cause a point of no return, according to recent work.

This is why “every fraction of a degree counts”, insists the IPCC, while another breaking point could see the Amazon – one of the lungs of the planet with the oceans – transformed into a savannah.

Faced with these systemic problems, there is no single miracle cure. In contrast, a single action can have positive cascading effects.

For example, the conservation and restoration of mangroves and submarine kelp forests, referred to as “blue carbon” sinks, increase carbon storage, but also protect against flooding, while providing habitat for many species. and food for coastal populations.

Despite its alarming conclusions, the report thus offers a note of hope. Humanity can still orient its destiny towards a better future by taking strong measures today to slow down the runaway of the second half of the century.

“We need a radical transformation of processes and behaviors at all levels: individuals, communities, companies, institutions and government,” argues the report.

“We must redefine our way of life and of consumption”.

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