Even if we start to fix climate change, the proof may not show up for 30 years
The young climate activists clamoring today for rapid cuts to the world’s fossil fuel emissions could be well into their 30s or 40s before the impact of those changes becomes apparent, scientists said in a study published Tuesday.
The new research finds that even if humans sharply reduce greenhouse gas emissions now — cutting carbon dioxide, methane and other pollutants by at least 5 percent or more a year — it could still take decades before it’s clear those actions are beginning to slow the rate of the Earth’s warming.
The coronavirus pandemic, with its notable but fleeting dent in global greenhouse gas emissions, has demonstrated how hard it will be to repair the impacts humans are having on the planet, particularly on the ambitious time frame scientists say is necessary to avoid the most catastrophic impacts of climate change.
An empty street in San Francisco during California's sheltering-in-place order in April 2020. Emissions declined by as much as 17 percent in early April, compared with the previous year, but then bounced back rapidly as shuttered economies around the world began to reopen. Overall, the globe’s 2020 emissions are likely to show only a single-digit drop from 2019 levels, experts project.
A comparable reduction would need to happen year after year for rising global temperatures to level off. A United Nations report in the fall found that the world’s emissions would need to shrink by 7.6 percent each year to meet the most ambitious aims of the Paris climate agreement, which has the support of nearly every nation except the United States under President Trump.
So far, any impact of the pandemic on the globe’s temperature is unclear. This year could very well be the hottest on record. Greenhouse gases in the atmosphere continue to rise relatively rapidly. Some regions saw a noticeable decline in air pollution, but that could prove temporary.
Samset said, “Luckily, we are moving to an era where we will see cuts in emissions. But we also realize that people are expecting to see some return on these efforts. This will impact people’s livelihoods. What do we get in return? We get reduced global warming at some point, but that may not be visible for 15, 20 years — longer if we are unlucky.”
Ken Caldeira, a longtime researcher at the Carnegie Institution for Science who has served as a lead author on key U.N. climate reports, was not involved with Tuesday’s paper but said he was not surprised by its findings.“The idea that we would not be able to statistically detect the influence of policy on global mean temperatures for many decades is the sort of thing that I believe is well understood by most working climate scientists,” he said, “but not well understood by many members of the general public.” Read original full article
+34 910 180 818 
+44 20 3514 1012 
