Does the impact of climate change happen “faster than expected”? From the rise in sea level to the rise of extreme events, the upheavals were announced a long time ago, underline the researchers, who admit however that they could sometimes underestimate the magnitude.
In Incheon, South Korea, the UN Climate Experts Group (Giec), meeting with governments, is preparing to release Monday the latest state of knowledge on a warming of 1.5 ° C compared to the pre-industrial era, a horizon very close, in a world already hit by the rise of mercury and its effects.
“The things scientists promised for the future are happening,” said Jennifer Morgan, director of Greenpeace International. “We thought we had more time, but no.”
“Unfortunately, almost everything was said 30 years ago”, also underlines Jean Jouzel, long vice-president of Giec, pioneer of glaciology. “This marked warming, which is superimposed on a resurgence of extreme events, is what we are seeing today!”
“There is a pretty sad side to seeing in the real world what climate physics has taught us for years,” adds climatologist Valerie Masson Delmotte, who is co-chairing the current meeting.
Climatologist Jean-Pascal Ypersele quotes the report “One planet”, prepared in 1972 for the first UN conference on the human environment, which spoke of “global and catastrophic effects” of a possible increase of 2 ° C due to CO2 emissions.
“Those who have underestimated the severity of climate change are rather the majority of political leaders, who have acted so little for so many years,” said the Belgian scientist, who sees two reasons: “the lack of interest for long-term issues, and the efforts of fossil fuel industry lobbies to instill doubt in climate change analyzes and solutions. “
Scientists also admit that they have often leaned towards caution.
For Pennsylvania State University Michael Mann, “projection models have been overly conservative, with a tendency to under-predict current impacts, including loss of Arctic pack ice, ice in Greenland or West Antarctic, and therefore the resulting rise of seas “. “The models also failed to capture the full impacts on extreme events such as those that hit North America, Asia or Europe this summer,” said the researcher, author of study describing phenomena in the Arctic that were poorly understood by the models.
Uncertainty is not our friend. The more we understand the physical processes, including them in the models, and the more we see that the impacts of climate change are likely to be stronger and faster than we first thought. “
The system of peer-reviewed scientific studies is highly conservative, adds climatologist Peter Frumhoff, today to the NGO Union of Concerned Scientists. “And then there is a cultural tradition in science and especially in climate science, which does not want to be too alarmist”.
Add to this the functioning of the Giec, which proceeds by consensus, and whose role is to specify which scientific conclusions are of a high degree of confidence and which are more speculative. The summary of its reports, intended for decision-makers, is adopted by governments, with which it is sometimes necessary to negotiate the formulation, as is the case in Incheon.
In any case, “the reports of the Giec reinforce one after the other but everything remains in the continuity of the first,” said Jean Jouzel, who lists the many areas of work for research. Whether it’s the magnitude of the rise of the sea – “some studies announce 80cm at the end of the century, some 3m! How to leave this sword of Damocles over the coastal regions! “- unknowns on the precipitation, or the need to know the regional impacts,” yes it is sure it will take a 7th report of the Giec! “