Amid all the hardships of the widespread coronavirus lockdowns this spring there has been one unintended but welcome consequence: less pollution, with cleaner skies and a drop in carbon dioxide (CO2) emissions. In fact, 2020 may see the largest yearly global decline ever in emissions. A new report from Carbon Brief is projecting a whopping 5.5% reduction from 2019; the head of the World Meteorological Organization says it could reach 6%.

An emissions drop of that size is about on par with the kind of year-after-year decrease the globe would need to sustain to achieve the goal set in the Paris climate agreement of keeping the Earth's warming from exceeding 2 degrees Celsius.

But clearly, shutting down economies is not an acceptable or sustainable way to accomplish this goal. Our current situation vividly illustrates that the kind of systemwide change needed to combat climate change is truly herculean, given that emissions are still tied directly to economic growth.

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It's this realization, and the question of how the pandemic will impact efforts to rein in emissions in the coming years, that are weighing heavily on the minds of those working on the problem of climate change.

"I'm most afraid that the virus will slow or even halt climate action," says Dr. Rob Jackson, head of the Global Carbon Project and a professor in the Earth System Science department at Stanford University.

He has good reason to feel that way. Research shows that after the Great Recession in 2008, a rather abrupt decline in public concern about climate change in the U.S. and Europe was most likely driven by economic insecurity. When faced with an immediate threat, like widespread unemployment, people tend to pay less attention to what they view as a more distant risk, like climate change.

Jackson is also concerned that rather than taking a strategic approach to economic recovery — built on the industries of the future — the government tends to react hastily in a crisis.

"When the goal is to prop up the economy and put people to work, governments throw money at everything," explains Jackson. "Some funds will go to renewable projects, but larger energy-intensive industries like fossil fuels and steel production will get much more. It's business as usual."

That "business as usual" approach of burning fossil fuels for energy has led to today's unprecedented carbon release rate — the highest the Earth has seen over the past 66 million years. In the coming weeks, our planet is still on track to break another record with CO2 concentrations peaking at around 416-417 parts per million, about 33% higher than before the Industrial Revolution in the 1800s.

You might ask, if emissions are going down this year, then why are harmful new records still being broken? That's because carbon dioxide stays in the atmosphere for thousands of years. It's like a bank account: The more CO2 you put in, the more CO2 concentrations build up, despite any short-term declines in emissions. As a result, concentrations are now higher than they have been in at least 3 million years.

The concern is that 3 million years ago — a pre-human period known as the Pliocene Epoch, when CO2 levels were equivalent to today — the Earth was a very different place, with giant camels roaming the Arctic near Greenland and sea levels 75 feet higher than today. In the coming decades, scientists project that the amount of carbon dioxide we've pumped into the atmosphere since the 1800s will have trapped enough heat to melt large sections of ice sheets, lifting sea levels to catastrophic levels.

Skeptics of climate science often wonder how CO2, a molecule that makes up less than a tenth of a percent of the atmosphere, can have such an outsized influence. The science behind the importance of carbon dioxide to climate is rather simple and also shocking.

Simply put, CO2 traps heat, creating a greenhouse effect. Because of its heat-trapping ability, that tiny portion of the atmosphere is largely responsible for keeping Earth's average temperature at a comfortable 60 degrees Fahrenheit. It's so powerful that if all carbon dioxide in the atmosphere abruptly dropped to zero, Earth's average temperature would plummet around 60 degrees in 16 years, turning the planet into an ice ball and eradicating most life as we know it.

To be clear, the drop in CO2 wouldn't directly cause the whole drop in temperature. The biggest impact in that hypothetical scenario comes from the most abundant greenhouse gas, water vapor, which condenses out due to the fact that colder air holds less water vapor; this is what would tank the greenhouse effect. Positive feedbacks like the growth of ice cover would further precipitate the temperature plunge. But it's CO2 which would drive the whole process.

Right now CO2, along with other greenhouse gases like methane, are driving change in the opposite direction at a destabilizing rate. In fact, temperatures are rising 10 times faster than at the time of the last mass extinction about 56 million years ago.

Given the implications and the arduous work ahead, the climate science community views this as a pivotal moment in the global challenge. With oil prices at record lows, the worst economic shock since the Great Depression and trillions of dollars in government relief flooding the market, our future could go either way.

"I see reasons for optimism and pessimism," says Jackson. On the optimistic side, "The virus can change the way we work — telecommuting could become mainstream, which can help reduce emissions and shave hours off commuting."

There's also the question of how the crashing oil markets may impact emissions going forward. Despite the lower demand for oil right now, Jackson feels a spike is inevitable. "Over time, low prices drive up demand and increase emissions," he said.

When asked whether the recent poor performance and volatility of oil prices will drive banks and other investors away, Jackson was skeptical: "I've seen enough downturns in the oil patch to know it always comes back."

But not everyone agrees. In an article Monday in Time magazine, Tom Sanzillo, director of finance at the Institute for Energy Economics and Financial Analysis (IEEFA), says, "The basic model is in pieces, it's fallen apart. This is an industry in last place."

He's not alone. In early February, before the widespread lockdowns, Jim Cramer, the host of "Mad Money: on CNBC, made waves when he said, "I'm done with fossil fuels ... they're just done. You're seeing divestiture by a lot of different funds. It's going to be a parade. It's going to be a parade that says, 'Look, these are tobacco and we're not going to own them'."

Even if this is the beginning of the end for oil, accomplishing the goals of the Paris Agreement are "extremely challenging," says Jackson. He feels that the pandemic can bolster action only if government relief is strategic.

"Long term, the coronavirus pandemic will help combat climate change if stimulus funding boosts green infrastructure and creates jobs in sustainable projects in renewables and electric cars," he said.

In a roundabout way there is evidence that some sustainable funding may happen as a result of a confluence of two events. Because of the pandemic, all 50 states now have "major disaster" declarations, which means billions of dollars in disaster relief will likely flow from the federal government to states.

That, in combination with a 2018 law requiring states to spend a percentage of disaster funds on projects that offer protection from hazards — like thinning forests to lessen fire risk and protecting communities from flooding — may turn what was expected to be an annual $500 million in funding into several billion.

While there is no way to predict the level of ambition for climate action when the world emerges from this emergency, or whether governments will seize on the opportunity to use disaster relief wisely, Jackson says that without proactive measures we are sure to fall short of our climate goals. "Emissions will jump back up, making the 2-degree goal unlikely," he said — and an opportunity to rebuild a more sustainable future might be lost forever.