Climate: decades before we see lower temperatures

Climat: des décennies avant de voir baisser les températures

Photo: Arun Sankar Archives Agence France-Presse

A significant decline in emissions can immediately see on the concentrations of CO2 in the atmosphere, but not on rising temperatures which is responsible for the propagation of the events the extreme weather.

Even if the world drastically reduces the emissions of greenhouse gases, the impact on global warming could not be visible before the middle of the century, according to researchers who are concerned about a reaction to boomerang in the face of measures that would appear to be wrong ineffective.

Due to human activities, the planet has already earned at least +1 °C since pre-industrial times, increasing disasters of climate.

To fight against the climate disruption known to worsen with each half-degree further, the signatories of the Paris agreement of 2015 have committed to reduce their emissions to limit warming to +2 °C, or even +1,5 °C.

For the moment, these commitments of the Member are not required. 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 in Nature Communications.

“The reduction of emissions, which is necessary, is effective as of the first day, but it will take time before we can measure this effect with certainty,’ says in a press release Bjorn Samset, from the centre of the Norwegian research on the climate of Cicero.

The climate system is in particular characterized naturally by a large force of inertia and a high variability from one year to the other.

“The climate change caused by Man can be compared to a container ship launched at full speed in the middle of big waves. If you want to slow down the ship, you can engage the reverse gear, but it will take time before you can notice that it has slowed down, ” says the climatologist.

Thus, a significant decrease of the emissions will be immediately on the concentrations of CO2 in the atmosphere, but not on rising temperatures which is responsible for the propagation of the events the extreme weather.

Even in the most optimistic scenarios, the first signs of a warming impact could be invisible at least until 2035, according to the researchers.

So please be patient !, argue-they, fearing that this delay does not cause a boomerang effect.

This reality “must be clearly explained to decision-makers and the population, if we want to avoid a negative repercussion against policies to mitigate emissions would be perceived as ineffective,” insists the study.

“This is not to say that the downward (emission) has no effect. It simply means that we need to be patient, ” insisted Bjorn Samset.

“We have stored problems for our future. But this is not a reason not to limit the damage now, ” commented Grant Allen, a researcher at the university of Manchester, not involved in the study. Even if at the same time, it will be necessary to adapt to the consequences already scheduled, he noted.

Several other scientists praised the new study but Piers Forster, a climatologist at the university of Leeds, has challenged its conclusions, calling them a ” vision dark and useless to our influence on the climate in the decades to come.”

“According to our own works, the company can have a noticeable impact of the decrease of the temperature of the planet in the next 15 to 20 years thanks to major efforts in reducing emissions “, he insisted.

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