"Regulating this largely gambling-driven source of carbon emissions attempts to be a simple means to contribute to decarbonizing the economy," researchers write. (Photo: Jack Guez/AFP/Getty Images)

You can probably guess which human activities emit the most carbon dioxide into the atmosphere; they include transportation and agriculture, of course, plus all the energy we use to power our homes and offices.

New research points to another, less-obvious contributor to climate change: cryptocurrency.

A new study reports that the annual carbon emissions associated with the creation of Bitcoins are equivalent to those of Kansas City, Missouri—or a small nation. Add in the other cryptocurrencies, and the emissions level more than doubles.

"Participation in the Bitcoin blockchain validation process requires specialized hardware and vast amounts of electricity, which translates into a significant carbon footprint," writes a research team led by Christian Stoll of the Technical University of Munich and the Massachusetts Institute of Technology's Center for Energy and Environmental Policy Research.

"Regulating this largely gambling-driven source of carbon emissions attempts to be a simple means to contribute to decarbonizing the economy," the team writes.

In the journal Joule, the researchers calculate the cost in carbon emissions of "mining" the online currency. That's the process by which Bitcoins are created and transactions recorded in the blockchain, a public ledger.

"Bitcoin 'miners' guarantee a system without fraud by validating new transactions," Cell Press, publisher of the journal, noted in announcing these findings. "Miners solve puzzles for numerical signatures, a process that requires an enormous amount of computational power. In return, miners receive Bitcoin currency."

As Pacific Standard reported last year, environmentalists have suspected for some time that this mining process is a prime example of wasteful energy consumption. But determining precisely how much energy was required for crypto-mining has proven hard to measure.

Utilizing such sources as initial public offerings of major hardware manufacturers and "insights on mining facility operations," Stoll and his colleagues estimated the annual electricity consumption of Bitcoin. "We then translated our power consumption estimate into carbon emissions, using the localization of IP addresses," the team writes.

Using that methodology, they concluded that the annual emissions produced by Bitcoin "sit between the levels produced by the nations of Jordan and Sri Lanka, which is comparable to the level of Kansas City," they write.

The news only gets worse. Including the output of three additional cryptocurrencies "more than doubles the power consumption we estimate for Bitcoin," the team reports.

Furthermore, "during 2018, the computing power required to solve a Bitcoin puzzle increased more than fourfold until October, and heightened electricity consumption accordingly," the researchers add. The associated greenhouse gas emissions will presumably grow at a similar rate.

Admittedly, these mining processes make up only a sliver of our total carbon output. But heating our homes and cooking our food are essential to life. No one can say the same about Bitcoin.

"We do not question the efficiency gains that blockchain technology could, in certain cases, provide," the researchers write. "However, the current debate is focused on anticipated benefits, and more attention needs to be given to costs."

That makes more than a bit of sense.