Climate: scientists are expressing ever-stronger alarm and making proposals

Changes that are already “irreversible” for human beings

The rise in ocean levels by at least 1 metre by 2100, small islands threatened with submersion, disappearing glaciers, and so forth. The IPCC notes that certain devastating impacts of climate change are already “irreversible”.

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Whereas in the last century the ocean rose by an average of 1.4 mm a year, this rise is now 3.6 mm, driven by the thermal dilation of the oceans as they progressively warm, and above all the melting of the ice caps of Greenland and Antarctica. Highly populated deltas and coastal regions will therefore be increasingly exposed to floods and other extreme meteorological events such as cyclones.

Even in an “optimistic” scenario of a world at +2°C, a large number of megacities and small islands will be hit from now to 2050 at least once a year by extreme weather events that previously occurred only once every 100 years. In the worst-case scenario, one billion people will be affected by rising sea levels from now to 2050 and there could be 280 million climate migrants by 2100; climate migrants fleeing rising seas, the loss of their land infiltrated with salt or the disappearance of their livelihoods as fishermen.

 

Acidification and the loss of oxygen in the oceans

The damage won’t occur only to human beings; the changes will be just as severe for other living organisms.

Taken alone, the oceans have absorbed more than 90% of the surplus heat introduced into the Earth’s system by human greenhouse gas emissions produced since the Second World War. They also absorb from 20 to 30% of our CO₂ emissions. The cryosphere, the name given to all the ice covering the Earth, is also a powerful carbon and heat sink. The oceans have therefore been warmed continuously (warming that has doubled since 1993!) and their services risk being considerably modified since it is becoming acidified and losing oxygen.

Proof of this is the expansion of dead zones from 3 to 8% of the surface of oceans between 1970 and 2010, due to the effect of warming and also to excess nitrogen and phosphorous generated by intensive agriculture and the discharge of untreated wastewater that runs into rivers that then flows into the oceans.

In particular, these changes lead to a decrease in plankton, the main food of fish, and weaken the capacities of many species to adapt. Those species that can tend to migrate towards the poles – they have been moving by 30 km to 50 km a decade since the 1950s.

To offset all these effects, the reporters plead for the restoration of natural habitats: mangroves, coral reefs, sea meadows, beaches and dunes that provide the best breakwaters for lessening the impact of waves while preserving a wealth of biodiversity.

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An immense appeal by scientists to save the Earth

Not long after the release of this IPCC report, more than 11,000 climatologists, biologists, physicists, chemists and agronomists from 153 countries signed an appeal published on 5 November in the review revue BioScience. They warned that human beings risk “indescribable suffering” linked to the climate emergency and called for worldwide changes in our lifestyles in order to preserve life on Earth, “our only home”.

This was not the first time that scientists have sounded the alarm. Forty years ago, in 1979, researchers from fifty countries, led by the biologist William Ripple (University of Oregon, United States), gathered at the first world conference on the climate, in Geneva, and warned of the need to act against climate change. Since then, other warnings have multiplied, on the occasion of the Earth Summit of Rio in 1992, the adoption of the Paris Agreement in 2015 and in numerous reports from the Intergovernmental Panel on Climate Change (IPCC). Again, at the initiative of William Ripple, 15,000 scientists warned of the disastrous degradation of the environment and the living world in 2017, in a manifesto published in the same review.

 

Are these efforts pointless? World emissions of carbon dioxide (CO₂) from fossil fuels and stemming from human activities continued their relentless progression and should reach a record level in 2019, at 37 billion tonnes. The only glimmer of hope according to the annual assessment of the Global Carbon Project published at the beginning of December is that growth slowed down this year due in a fall in recourse to coal. However, if we consider emissions linked to deforestation and other changes in land-use (the destruction of prairies, etc.) – that are progressing due to wildfires in the Amazon region, the estimations of which are highly uncertain – the total emission should reach 43.1 billion tonnes of CO₂ in 2019.

Levers for action to face the magnitude of the crisis

Whatever the case, these repeated appeals by scientists make denial difficult, even if there is a big step between knowing and believing, becoming aware and political action. Above all, they show the magnitude of the crisis facing the 196 countries that met recently at the United Nations Climate Conference (COP25) in Madrid, and it should incite them to raise their ambitions. With every new study, the forecasts announced are even more ominous than the previous diagnostics. The indicators point to a climatic crisis that is accelerating faster than has been predicted and its consequences are increasing at a faster pace, especially in the world’s poorest regions.

Scientists have therefore decided to assist politicians in their decision-making and multiplied their recommendations. Their latest appeal proposed six levers of action including the abandoning of fossil fuels, a reduction in meat consumption, the protection of ecosystems, etc. So, have they have left their neutrality as experts by the wayside in writing a text of opinion? This is the criticism levelled at them by some, regarding their proposal to control demography. The contribution of economic and social sciences to the diagnostic would certainly strengthen their recommendations and give even more power to their warning.