Science

Hunger, disease, extreme heatwaves … IPCC warnings on global warming

The impacts of climate change are already devastating and “the worst is yet to come”, details the 4000 pages report written by the Intergovernmental Panel on Climate Change (IPCC). This text by the UN climate experts is much more dramatic than the previous one from 2014. Nearly 2.5 billion additional people will be affected by 2050 by climate risks, from heat waves to floods, including impact on agriculture. While the report is due to be published in February 2022, i.e. after the important climate conference of COP26, scheduled for November in Glasgow (Scotland), here are the main conclusions of this text which evokes already inevitable impacts.

  • “Irreversible impacts”

A lasting global warming above the threshold of + 1.5 ° C would have “irreversible impacts on human and ecological systems”, warns the report. The 2015 Paris Agreement set a maximum warming target of + 2 ° C compared to the pre-industrial era, and if possible + 1.5 ° C. But the current trajectories do not allow to reach them according to the scientists. “Life on Earth can recover from major climate change by evolving into new species and creating new ecosystems. Mankind cannot,” warns the 137-page technical summary.

Life on Earth as we know it will inevitably be transformed by climate change when children born in 2021 turn 30, or even earlier, the text points out. 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.

  • Strong heat waves

If the temperature rises from + 1.5 ° C to + 2 ° C, 1.7 billion additional people will also be exposed to extreme heat, 420 million to extreme heat and 65 million to exceptional heat waves every five years. These scorching episodes will undermine the limits of human resistance to heat. Even more than in absolute heat, whose records are already falling regularly, the ability to resist these extremes is assessed by a concept known to scientists: the “wet temperature” or “wet thermometer”, transcribed by the acronym “TW “.

This measurement takes into account the ambient relative humidity and its possibilities of evaporation. Knowing that a body cannot lose heat if this outside temperature TW exceeds its own, scientists agree: humans cannot survive for long at 35 degrees TW.

  • Water scarcity and malnutrition

Up to 80 million more people will be at risk of hunger by 2050, a cascading consequence of poor harvests, declining nutritional value of some products and soaring prices. “Human health rests on three pillars: food, access to water and shelter. They are vulnerable and threaten to collapse,” analyzes Maria Neira, director of the Department of the environment, climate change and health from the World Health Organization.

On the water supply side, just over half of the world’s population is insecure. And nearly 75% of groundwater supplies – the main source of drinking water for 2.5 billion people – could be impacted by climate change by 2050, when melting glaciers have already “strongly affected the water cycle “(streams, seas, evaporation, rain).

Lack of water could endanger rice cultivation in 40% of producing regions, while world maize production has already fallen by 4% since 1981 due to climate change, millet and sorghum by 20% and 15% respectively. The frequency of bad harvests has increased steadily for 50 years and the increase in extreme weather events will increasingly affect production. Fishing will also be affected, with potential catches falling by 40 to 70% in tropical areas of Africa.

Another consequence, more than 10 million additional cases of malnutrition or infantile rickets are expected in Africa or Asia by 2050. The regions of the world “where agricultural production will be most affected by the climate (…) are also those where populations already suffer from high rates of malnutrition, “notes Elizabeth Robinson, professor of environmental economics at the UK University of Reading.

  • Many threatened ecosystems

Forests, tropical or boreal, are particularly concerned, with increasing temperatures, aridity and fires. In a pessimistic scenario, the Amazon could even reach a point of no return and partly turn into a savannah, depriving the world of a carbon sink essential to curb global warming.

The extinction of animal and plant species – not only linked to global warming – is said to be 1000 times faster than in the middle of the 19th century. With a warming between +2 and + 3 ° C, up to 54% of land and marine species could be threatened with extinction by the end of the century. Even at + 2 ° C, polar fauna (penguins, seals, bears) will be threatened. And at just 1.5 ° C, 70-90% of coral reefs are in danger.

  • Diseases will increase

Warming is expanding the areas suitable for disease vectors, especially mosquitoes. By 2050 half of the planet’s inhabitants could be exposed to dengue, yellow fever or viruses like zika. The ravages of malaria or Lyme disease will increase and deaths from childhood diarrhea will increase at least until the middle of the century, despite socio-economic development.

Diseases related to air quality, including ozone pollution, typical of heat waves, will also “increase substantially”. “There will also be increased risks of contamination of water or food” by marine toxins, warns the report. In addition, IPCC experts also anticipate pressures on health systems, such as those that appeared during the Covid-19 pandemic, with their “significant and negative consequences for the most vulnerable”.

  • Population displacements to be expected

Coastal cities are now threatened by the ocean which had allowed them to flourish, under the effect of global warming. From Bombay to Miami, Dhaka or Venice, these cities and their millions of inhabitants settled at the mouths of estuaries or on the sinuous lines of the coast are “on the front line” of the climate crisis which risks redrawing the maps of the continents. , worries about the draft report of the IPCC.

Therefore, the impacts of global warming will also force many families to abandon their homes. Floods, for example, will displace an average of 2.7 million people in Africa. By 2050, between 31 and 143 million people (depending on emission levels) in sub-Saharan Africa, South Asia and Latin America will be internally displaced due to water shortages, pressure on agriculture and rising sea levels. Among the concrete examples, Indonesia has already planned to transfer its capital Jakarta to Borneo.

  • Economic growth at half mast

Extreme weather events reduce economic growth, in the short term, after a disaster, and up to ten years after, especially in poor countries. Even with adaptation measures (dikes, drainage …), the costs related to flooding could by 2050 be multiplied by ten, to 60 billion dollars per year, in the 136 largest coastal cities.

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If the planet gains + 4 ° C, a worst-case scenario, global GDP could be 10 to 23% lower than in a world without warming. Industrial infrastructures are threatened: the ports are on the front line in the face of rising sea levels, but also nuclear power plants, 40% of which are installed near the coast. Tourism will also pay the price, with the erosion of the beaches or the decrease in snow cover.


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