For our planet, what would be the difference between an increase of 1.5 degrees and an increase of 2 degrees? We don't know, because scientists have barely begun to do any research specific to the 1.5 degree target.
Ihere is a "paucity of scientific analysis" on the degree and a half, says one in a analysis published on June 6 in Nature Climate Change. The Oxford University team stresses the importance of the issue, even though this target was repeatedly stressed at the Paris Conference in December.
The consequences of an increase of 2 degrees Celsius compared to pre-industrial average temperatures are themselves approximate Between Arctic ice, Atlantic hurricanes or ocean acidification, no one can draw a clear line at which things start to degrade for our environment. But a consensus emerged in the 1990s and 2000s that the two-degree bar marks the entry into a danger zone. Already, with "only" one degree Celsius increase - a threshold we have just reached - experts from disciplines as diverse as glaciology, oceanography and biology can determine tangible consequences. What will happen when the planet reaches one and a half degrees?
Extreme weather events will occur more often. But what does "more often" mean, if it varies with each type of extreme event and geographic region? Pessimistic scenario: according to Erich FischerAccording to a study by the Institute for Climate and Atmospheric Sciences in Switzerland, a catastrophic event once described as "one per 1000 years" would double to "one per 500 years" with one and a half degrees, and double again to two degrees.
Increased droughts in Africa, Central America and the Mediterranean basin, according to Carl-Friedrich SchleussnerThe project is being carried out by the Postdam Institute for Climate Impact Research in Germany. Last year, he predicted a decline in river flows in these regions of between a third and a half.
Experts have recently said that with the two-degree threshold, entire regions of the Persian Gulf and Southeast Asia would be downright uninhabitable unless they were to remain in an air-conditioned room forever. But at one and a half degrees?
Same question for a good part of the agricultural land that is today indispensable for the survival of part of humanity. With one degree, they are already suffering, with two degrees, much of their productivity will decline.
To a degree and a half," summarizes journalist Fred Pearce in Yale E360In the Arctic, we are preventing some of the frozen ground from thawing, thereby limiting the release of billions of tonnes of methane into the atmosphere. At two degrees, it's less safe.
Only one thing is now clear amidst all these uncertainties: our planet will reach the threshold of one and a half degrees of increase during this century, no matter how fast we stop emitting greenhouse gases. The whole question is how far we will allow the increase to continue afterwards.