Global warming only cares about one number: The amount of carbon amassing in the atmosphere.
And the amount of the most important greenhouse gas, CO2, is skyrocketing. It's a rate of increase that's unprecedented in the geologic record. What's more, heat-trapping atmospheric CO2 levels, now exceeding 414 parts per million, are the highest they've been in some 3 million years.
Crucially, even the worst pandemic in a century — with unparalleled disruptions to daily life and transportation — failed to meaningfully slow the continued rise of atmospheric CO2. Two new reports from researchers with the Global Carbon Project, an international science group that tracks greenhouse gases, show that after an unprecedented 2020 drop in CO2 emissions from fossil fuel burning, emissions have essentially rebounded to pre-pandemic levels as economies restarted their engines.
This reality underscores how transformative systemic change, like economies and transportation largely powered by renewable energy, are needed to radically slow Earth's relentless warming. This hasn't yet occurred.
"We haven't changed the world's infrastructure in any fundamental way," Rob Jackson, a professor of earth system science at Stanford University who worked on both reports, told Mashable. "We expected fossil carbon emissions to snap back when the world's economies recovered. That's what happened."
The new reports are published online in the journal Earth System Science Data and the science preprint site arXiv.
In 2020, CO2 emissions from fossil fuel burning dropped 5.4 percent from 2019 levels to (a still colossal) 34.8 billion tons of CO2. "It was the biggest drop we've ever seen," Jackson said. But the latest estimates found that 2021 emissions (at some 36.4 billion tons of CO2) will nearly rebound to 2019 levels.
Importantly, the recent CO2 dip and subsequent rebound are really peanuts in the greater carbon picture. The pandemic-induced 2020 drop was never something to get too excited about. Society still emitted bounties of carbon into the atmosphere. "Being thrilled about 'only' 34.8 [billion tons] of CO2 in 2020 is like saying you've cut back on smoking to only 19 cigarettes per day instead of 20," said Kristopher Karnauskas, a climate scientist at the University of Colorado Boulder who had no involvement with the research.
The total amount of atmospheric carbon (currently at some 414 ppm) is like a bank account. Each sum of annual emissions is like a deposit. That's why, even with a five percent lower emissions deposit in 2020, Earth's total levels of atmospheric CO2 still went up.
The good news is there are large-scale, momentous solutions for cutting carbon, and they are known. It's not rocket science (or, more aptly, nuclear fusion). For example, in highly-populated coastal regions there's the expansion of reliable, off-shore wind farms that produce bounties of energy. But these are not easy, nor cheap, solutions to deploy. That's why global nations are now attending their 26th UN climate conference ("COP26"), and atmospheric CO2 is still going up.
"That trend is going to be really hard (but not impossible) to slow down," explained Karnauskas. "For the concentrations of greenhouse gases in the atmosphere to actually decline (not just slow down the rise), we will have to basically stop emitting carbon into the atmosphere."
Global leaders at COP26 are meeting to find ways to avoid the worst consequences of climate change, the likes of collapsed ice shelves, unprecedented droughts, and catastrophic storms. This means slashing emissions enough to stabilize Earth's climate at some 1.5 to 2 degrees Celsius (2.7 to 3.6 degrees Fahrenheit) above pre-Industrial Revolution temperatures. With current carbon-cutting commitments from world nations, the world is on track to warm by some 3 C (5.4 F), which would have extreme, disastrous environmental consequences.
While individual choices do of course matter some (eating less meat, using public transport, and avoiding extremely wasteful single-use plastics are healthy and societally responsible things to do), the COP26 summit is about pushing nations to make robust, society-wide changes that momentously limit emissions (like electrified transportation). As our energy paradigm exists today, even a homeless person has an unsustainably high fossil fuel footprint.
Amid the pre-vaccine pandemic in 2020, the global drop in emissions was largely caused by a drop in the burning of oil and coal. In the U.S., for example, motor gasoline consumption dropped by 14 percent. Now it's rising again, but in positive news, may stay somewhat lower as more workers continue working from home. Meanwhile, coal use fell in China and India during the pandemic, but has now sharply rebounded.
"While we saw big drops, we're now seeing big increases," noted Jackson.
"While we saw big drops, we're now seeing big increases."
The new reports include a dose of optimism amid the looming challenges ahead: proof that national economies can still advance with clean energy. The researchers found that 23 nations saw "significantly decreased" CO2 emissions while their economies grew in the decade before the pandemic hit. These countries include the likes of the UK, the U.S., Germany, and Japan.
Since humanity started burning fossil fuels for power (around 1850), the U.S. has emitted the most heat-trapping carbon of any nation, and still remains one of the four largest emitters today (together with China, India, and the European Union). One of the goals of COP26 is to get the big four to commit to sizable carbon reductions this year.
To eventually stabilize the climate (ideally at around 2 C or less), global carbon emissions must drop to zero, and stay there. That's because the CO2 already in the atmosphere (the "bank account") doesn't just rapidly vanish. It takes ages for the oceans and earth to soak up this potent greenhouse gas.
"The problem is it stays there for centuries," said Jackson.
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