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作者:探索 来源:焦點 浏览: 【大中小】 发布时间:2024-11-22 00:33:59 评论数:
Eye-opening, powerful words are now used to describe plummeting CO2 emissions in 2020.
It “would be the largest decrease in emissions ever recorded,” the International Energy Agency saidThursday. Spurred by an unprecedented energy shock, carbon emissions would take “a far bigger drop than at any point during the Great Depression or at the end of World War II, when much of Europe lay in ruins,” notedthe New York Times.
This is all likely true. We’re headed for some major emission declines. But, critically, the true number global warming cares about — the amount of carbon dioxide saturating the atmosphere — will barely be impacted by an unprecedented drop in carbon emissions this year, a drop the International Energy Agency estimates at nearly eight percent (compared with historic 2019 levels).
That’s because atmospheric CO2 levels are like a massive bank account that’s been accruing more and more carbon every year for well over a century (this bank account is now at its highest levels in at least800,000 years, but more likely millions of years). This year’s carbon emissions, however, are just a deposit. This 2020 deposit may be smaller than in 2019, but it’ll still add to the atmospheric CO2 bank account.
“It will still be a big increase over last year,” said Zeke Hausfather, a climate scientist and director of climate and energy at the Breakthrough Institute, an environmental research center, referencing atmospheric CO2 levels. “It’s not fundamentally changing the trajectory of where the world is headed,” he added.
The world is headed for significantly more warming this century, unless CO2 emissions are radically slashed, year after year. With current, relatively weak global climate policies, Earth is set to warm by some 3 degrees Celsius, or 5.4 degrees Fahrenheit, above pre-Industrial Revolution temperatures by the century's end.
Yet a sizable drop in emissions this year, stoked not by robust climate policies but a microbial parasite that causes a grim respiratory disease, won’t tame Earth’s warming — even if emissions drop by a whopping eight percent in 2020.
“We’re still emitting 92 percent of a very, very large number,” said Kristopher Karnauskas, a climate scientist at the University of Colorado Boulder.
This means, by year’s end, we’ll be puffing about the same amount of carbon into the atmosphere as we were in 2010. Yes, we’ll still be adding over 30 gigatonnes — or 30 billion metric tons — of CO2 to the atmosphere this year.
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These still large 2020 emissions certainly won’t lower atmospheric CO2 levels, but could slightly slow the continued increase in Earth's burgeoning CO2 bank account. “Doing it one year isn’t going to have a significant effect on CO2 levels,” said Karnauskas.
To illustrate, before the pandemic and ensuing economic shock, Earth’s average atmospheric CO2 concentration was expected to averagearound 414.2 parts per million, or ppm, this year. With a five percent drop in emissions, this would fall to just 414.0 ppm, explained Hausfather. And with an eight percent emissions reduction, it would drop slightly more to around 413.9 ppm. Importantly, this is still much higher than average CO2 concentrations last year, which averaged 411.5 ppm.
So, yes, carbon emissions will likely fall, but barely. Yet, throwing the global economy into disarray to achieve these cuts isn’t reasonable. It's destructive and inhumane.
“What this really tells us is that economic shocks are not a great example of how to decarbonize because they’re not sustainable,” said Hausfather.
"We need systematic change."
With huge swathes of society shut down — restaurants, bars, national parks, and many workplaces — it seems like there should be an even larger projected drop in CO2 emission this year, not just some eight percent. Much of society, however, is still consuming lots of energy.
“It’s only transportation that has changed radically,” explained Rob Jackson, a professor of earth system science at Stanford University and director of the Global Carbon Project, which researches carbon emissions. “Outside of transportation, emissions are not changing all that much,” he said. For example, we’re still using lots of electricity at home.
However much emissions ultimately drop this year — whether five percent, eight percent, or more — there will be a big rebound in emissions once people start driving and traveling again. After every economic shock of the past century there’s been a rebound, most recently in 2010 after the Great Recession, when emissions rose by five percent, Jackson said.
Skyrocketing atmospheric CO2 concentrations.Credit: nasaUnfortunately, the U.S. transportation sector largely runs on fossil fuels, which means big carbon emissions — in fact, the transportation sector is the leading contributor of heat-trapping greenhouse gas emissions in the U.S. Electric vehicles only make up about 1.8 percent of cars purchased in the U.S. today. And, globally, lower-emission fuels from airliners (“biofuels”) made up less than one-tenth of one percent of aviation fuels burned in 2018.
“If we just hop back in our cars, this will be a one-year blip on the emissions record and it won't amount to much in five or 10 years,” said Jackson. “It won’t matter.”
“We need systematic change” to really drive down emissions, he said.
In the realm of transportation, this means government support of a nation-wide electric vehicle charging systemso people are encouraged to buy electric cars — like the bill proposed by Congresswoman Alexandria Ocasio-Cortez and Congressman Andy Levin for powerful, fast-charging stations.
It also means ramping up renewable energies so they become the dominant means of producing electricity. In 2018, renewables accounted for around 11 percent of energy consumptionin the U.S. “We need to deploy clean energy technologies at a very large scale,” said Hausfather. (Renewables are expected to rise in useduring the pandemic, in large part because they’re cheaper than coal.)
To curb Earth’s warming at levels that would avoid the worst consequences of climate change, the United Nations says global emissions need to drop by 7.6 percent each yearfor the next decade— without, of course, introducing sharp economic shocks. But if society waits longer to cut emissions in a meaningful, sustainable way, curbing future warming will require even more drastic measures. It’s similar, then, to waiting to seriously respond to a growing pandemic, which has mired the U.S. in economic despair, agony, historic shutdowns, and continued death.
“The earlier you act, the less severe of actions you have to take,” said Karnauskas.
TopicsCOVID-19