Even if the world drastically reduces greenhouse gas emissions, the impact on global warming may not be visible before the middle of the century, according to researchers who feared Tuesday in the journal Nature Communications , a boomerang reaction to measures which would appear wrongly ineffective. Due to human activities, the planet has already gained at least + 1 ° C since the pre-industrial era, increasing climatic disasters.
To combat this climate change destined to worsen with each additional half degree, the signatories of the Paris Agreement of 2015 committed to reducing their emissions to limit warming to + 2 ° C, or even + 1.5 ° vs. For the moment, these State commitments are not fulfilled. Even if they were, "these efforts could be visible by the middle of the century, but probably not before," write the authors of the study published Tuesday. "The reduction in emissions, which is necessary, is effective from the first day, but it will take time before we can measure this effect with certainty," said in a statement Bjorn Samset, from the Norwegian climate research center Cicero.
"Climate change, a container ship launched at full speed amidst big waves"
The climate system is in fact naturally characterized in particular by a significant force of inertia and a high variability from one year to another. "Man-made climate change can be compared to a container ship launched at full speed in the midst of big waves. If you want to slow the ship down, you can reverse, but it will take time before you can notice that it slowed down, "continues the climatologist.
Thus, a significant drop in emissions can be seen immediately on the concentrations of CO2 in the atmosphere, but not on the rise in temperatures which is however responsible for the multiplication of extreme weather events. Even in the most optimistic scenarios, the first signs of an impact on global warming could be invisible at least until 2035, according to the researchers.
"A dark and useless vision of our influence on the climate in the decades to come"
So be patient !, they plead, fearing that this delay could cause a boomerang effect. This reality "must be clearly explained to decision-makers and the public if we are to avoid a negative backlash against policies to reduce emissions that would be perceived as ineffective," insists the study. "This does not mean that the decrease (in emissions) has no effect. It simply means that we have to be patient," insists Bjorn Samset. "We have piled up problems for our future. But that is no reason not to limit the damage now," said Grant Allen, a researcher at Manchester University, not involved in the study. Even if at the same time, we will have to adapt to the consequences already programmed, he notes.
Several other scientists welcomed the new study, but Piers Forster, a climatologist at the University of Leeds, disputed its findings, calling them "a bleak and useless vision of our influence on the climate in the decades to come". "According to our own work, society can have a noticeable impact of a drop in the temperature of the planet in the next 15 to 20 years thanks to significant efforts to reduce emissions," he insisted.