The first part of the sixth report of the Intergovernmental Panel on the climate, made public on Monday, warns of a generalization of the dangers linked to the acceleration of global warming. The objective of + 1.5 degrees provided for by the Paris climate agreement, unless an extraordinary effort is made, is no longer tenable.
Unless it finally decides to immediately embark on a titanic effort to reduce greenhouse gas (GHG) emissions, the international community can abandon the main objective of the Paris climate agreement. concluded in 2015 . The limit of 1.5 degrees of warming, which this agreement sets for 2100, “will be exceeded over the next few years”, estimates the Intergovernmental Panel on Climate Change (IPCC) in the first part of the 6th report that this UN scientific body made public this Monday morning and a provisional version of which had been leaked to the press at the end of June.
The red line has already been crossed on dry land with a 1.59 degree rise in temperature observed since 1850. This level is not yet observed in the oceans where the mercury has risen by 0.88 degree over the same period. But that will not be long in coming, as the trend is far from slowing down. The values displayed on thermometers over the past decade have been on average higher than in the previous one.
This responsibility “is an established fact”, insists Véronique Masson-Delmotte, co-chair of the working group 1 of the IPCC which produced this river report, resulting from the review of 14,000 scientific publications which mobilized for 3 years more than 230 experts from 60 countries. The 40-page summary drawn from it for policymakers puts the human-caused share of warming at 1.07 degrees.
A warming whose effects on the climate are accelerating and intensifying. Globally, heavy rainfall has increased since 1950 and its rate has accelerated since the 1980s. The rains are torrential in northern Europe, like those which occurred last month in western Germany. Storms observed in mid-latitudes tend to move towards the poles. Precipitation is getting heavier and heavier in the southern hemisphere at the same time that it becomes scarce and shorter there, opening up increasingly long periods of drought.
Man, the main culprit
A situation attributable to the increasing concentration in the atmosphere of CO2, the main agent of greenhouse gases causing global warming. Since 2011, their level, on an annual average, has stood at 410 ppm, a value that has never been so high for at least 2 million years. For the IPCC, this is the most obvious demonstration that human activities are the cause of the fever that has gripped the planet.
Impacts on the whole planet
Human influence is also, “very probably”, the main cause of the unprecedented retreat of glaciers since the 1990s and the decrease in ice surfaces in Arctic waters. It is just as “highly probable” that the human factor played in the melting, unparalleled for 2000 years, of the Greenland ice sheet observed over the last two decades and in the warming of the upper layer (between 0 and 700 meters). ) of the seas since the 1970s.
The oceans saw their level rise by 20 centimeters between 1901 and 2018, with an acceleration of movement at the end of the period. From 1.3 mm between 1901 and 1971, the average annual increase in the sea surface rose to 1.9 mm between 1971 and 2006, then to 3.7 mm between
2006 and 2018. Unprecedented, the effects of global warming do not spare any point on the planet. And it is not over because the IPCC takes for granted the continued rise in temperatures on land and at sea, albeit at a slower rate.
“Each additional half-degree will translate into longer and more intense heat waves, more rainfall, more severe droughts,” say its experts. The exceptional marine submersions, which until now occurred every 100 years, could be repeated every year at the end of this century. The melting of permafrost will increase and the Arctic ice will disappear completely in summer, points out this 6th report, the publication of which is accompanied by the posting of an interactive Atlas making it possible to visualize climate data and their impact in the summer. regional level.
The essential carbon neutrality
The climatologists of the IPCC have constructed five scenarios of climate change for the decades to come. All expect the temperature to rise further. In the rosiest scenario, the warming could be contained within 1 to 1.8 degrees. After marking a temporary rise of more than 1.5 degrees between 2021 and 2040, the level of mercury could start to fall. But on the express condition of achieving carbon neutrality in 2050, which requires a drastic reduction in CO2 emissions.
In contrast, the fifth scenario of the IPCC, the darkest of all, raises fears of a warming of between 3.3 and 5.7 degrees with, among other effects, causing an increase of nearly 2 meters in the level of oceans by 2100. This grim projection is based on a doubling of emissions by 2100 from their current level. In an intermediate scenario, based on a freeze on emissions until the middle of this century, the planet could not cut to a warming of 3.5 degrees, far away from the 2 degrees which constitutes the minimum target of the agreement of Paris.