Rising seas, loss of biodiversity, complicated access to food, lower standard of living… Even if the world manages to limit global warming to 2 ° C, the consequences will be significant, according to a study recently released.
“We detect significant changes in climate impacts for a world at 2 ° C, so we must take steps to avoid it,” said Dann Mitchell, of the University of Bristol, lead author of the text that introduces this special issue of the British journal “Philosophical Transactions of the Royal Society A.”
More than two years after the signing of the Paris agreement, which aims to keep the rise in global temperature under 2 ° C, or even 1.5 ° C, scientists are yet again sounding the alarm about the devastating impact that global warming in the future. “One of the challenges is how quickly we will reach 2 ° C,” says Mitchell. In other words, the time that the world will have or not to adapt to the multiple consequences of global warming.
The UN Climate Experts Group (Giec) is due to report in October on a possible planet at + 1.5 ° C. The draft text estimated in January that given current state commitments and CO2 emission trajectories, it was “extremely unlikely” to achieve the target.
Rise of the oceans
Even if the rise in temperature stabilizes at 1.5 or 2 °C, the sea level will continue to rise “for at least three centuries, by 90 to 120 cm by 2300, according to a study. This will result in flooding, erosion and salinization of groundwater.
If nothing is done to limit CO2 emissions, the average rise in sea level — caused by melting ice and water dilation — will reach 72 cm by 2100. But this prospect is pushed back by 65 years for the scenario at 2 °C, and 130 years for 1.5 °C. “The impacts for the 21st century are just postponed rather than avoided,” note the researchers. So “adaptation is essential”, insists Robert Nicholls from University of Southampton.
Access to food
Rising temperatures will lead to greater food insecurity around the world, with both floods and droughts becoming widespread and more severe, warns one of the studies.
With a warming of 2 °C, Oman, Bangladesh, Mauritania, Yemen and Niger would be the most vulnerable countries to the shortage. On the contrary, Mali, Burkina Faso and Sudan would see their situation slightly improve as they would suffer from less severe droughts. But this is an “exception,” says Professor Richard Betts, who led the study.
In case of a warming of 1.5 °C, “76% of the countries studied would record a lower increase in their vulnerability to food insecurity than when studied with the 2 °C model.
Growth of inequalities, poor countries will poorer
If 1.5 ° C is not expected to change much in global economic growth, “a warming of 2 °C suggests significantly lower growth rates for many countries, especially around the equator”, says Felix Pretis, economist at Oxford University.
The difference is even greater with GDP per capita. By the end of the century, it would be 5% lower if warming reaches 2 °C rather than 1.5 °C, according to this study. In addition, “countries that are poor today should become even poorer with climate change, and more in the case of 2 °C , while rich countries are likely to be less affected,” says Felix Pretis.
Impact on the Biodiversity
If a rise in temperatures will disrupt some of the fauna and flora, “containing the warming at 1.5 ° C rather than 2 ° C (…) would increase from 5.5 to 14% areas of the globe that could serve as a climate refuge for plants and animals,” according to another study. Their area would be equivalent to that of the “current network of protected areas”.
In addition, limiting warming could reduce by up to 50% the number of species at risk of halving their natural habitat.