You probably at least heard about the latest big U.S. climate report -- even though the Trump Administration attempted to furtively release it on Black Friday. In the end the plan backfired, as many of the nation's top newspapers highlighted the grim conclusions of the Fourth National Climate Assessment.
Yet, that same day at the same time, another major climate report dropped: the latest edition of the State of the Carbon Cycle Report, which marked its first-ever update, over a decade after the inaugural release.
The three-year effort, involving the input of 200 scientists and 13 federal agencies, underscores that the carbon emitted from U.S. fossil fuel burning is fast outpacing the planet's natural ability store away this heat-trapping gas, leaving it to accumulate in the atmosphere.
While President Donald Trump may be candid about dismissing his own administration's latest climate research, this report further shows the reality that Earth's climate has moved into some profoundly unfamiliar climate territory. Carbon dioxide concentrations themselves are the highest they've been in some 15 million years, and human activity is to blame.
The carbon cycle in North America.Credit: USGCRP 2018, adapted from Ciais et al., 2013; Copyright IPCC, used with permission."It's certainly true that we are emitting a lot more carbon into the atmosphere than the oceans and land are taking up," Elisabeth Larson, a NASA scientist who worked on the report, said in an interview. "That is the main reason we are seeing global warming."
Earth's vast oceans and sprawling forests, while naturally quite proficient at absorbing carbon and removing it from the air, can only take in so much at once. They are known as carbon "sinks," and they're maxed out. With the modern burning of prodigious amounts of fossil fuels, that leaves a profound amount carbon to saturate the air and trap heat -- a physical reality understood since the 1870s.
So, just how much carbon is filling the skies?
According to the report, in North America each year about 2,145 megatons of carbon saturates the air.
For perspective, there are over 2.2 billion pounds in every megaton. Comparatively, about half this number, some 1,136 megatons, is stored away in the continent's forests, oceans, and other vegetation each year. That leaves well over 1,000 megatons of carbon -- or hundreds of billions of tons -- left out in the atmosphere.
But the even more critical numbers come next: How much of this carbon comes from the human burning of fossil fuels?
SEE ALSO:How a quiet California town protects itself against today's megafiresMore than 80 percent of the carbon filling the air comes from fossil fuel burning, and the U.S. is overwhelmingly to blame.
"The U.S. is responsible for 80 to 85 percent of fossil fuels emissions in North America -- that's a lot," Gyami Shrestha, director of the U.S. Carbon Cycle Science Program and scientist at the University Corporation for Atmospheric Research, said in an interview.
That said, it's important to note one bit of brighter news.
Although over the last decade the U.S. economy has recovered from the crippling "Great Recession", and consequently ramped up its production, the nation has gradually started reducing carbon emissions.
In each of the last 10 years, carbon dioxide emissions have dropped by one percent, showing that the economy can still grow while reducing the amount of carbon spewed into America's proud, blue skies.
Before the industrial revolution began, Earth's climate was largely in balance, said NASA's Larson. Things were quite stable.
Carbon levels on Earth over the last 800,000 years.Credit: nasaFor at least hundreds of thousands of years, Earth's total carbon dioxide concentrations slowly wavered between 200 to 280 parts per million, or ppm. But in the last 150 years these numbers have skyrocketed. This year, they hit 410 ppm.
"Humans threw the climate-carbon equilibrium out of whack, and that will persist for thousands of years," Matthew Long, a carbon cycle expert at the National Center for Atmospheric Research who had no role in the new federal report, said in an interview.
There's little question Earth's great surplus of carbon is coming from humans.
When plants suck carbon out of the air, they consume a specific type of lighter carbon (technically known as a lighter carbon isotope), explained Larson.
Millions of year later, when these long-dead plants have decayed into oil, coal, and gas and are then burned as fuel, this carbon -- with its specific plant fingerprint -- is then released into the air.
Although Earth's natural systems are overloaded, they still absorb bounties of carbon from the carbon dioxide-saturated atmosphere.
"Ultimately, after thousands of years, the ocean will absorb most of the CO2," said Long.
But that's not quite the end of the story.
The Earth will try in earnest to balance itself back out.
Ocean acidification.Credit: noaaYet, as consequence, the oceans will grow increasingly acidic as they absorb more carbon. This wide-scale chemical change is a problem the National Oceanic and Atmospheric Administration (NOAA) terms the "the other carbon dioxide problem."
This has already proven deadly for life dwelling in the oceans, like corals and shelled-critters, both significant players in the food web.
The future holds another significant carbon threat on land, specifically in the Arctic -- a vast region warming between two and three times faster than the rest of the planet.
The considerable problem here is that warmer air will thaw once permanently frozen, nutrient-rich soil, called permafrost. It holds bounties of carbon.
"This increase can destabilize permafrost soils (i.e., soil that remains permanently frozen at some depth) and surrounding landscapes, which exist throughout the Arctic and store almost twice the amount of carbon currently contained in the atmosphere," the report reads.
"Warming temperatures can release this stored carbon into the atmosphere."
This carbon report, like the latest National Climate Assessment, is extremely detailed and leaves no portion of the Earth unanalyzed: Grasslands, oceans, marshes, and agriculture are all assessed.
And the message is clear.
"The carbon cycle is changing at a much faster pace than observed at any time in geological history," the report's authors write.
相关文章：
相关推荐：
