In medieval Europe, the Roman Catholic church encouraged sinners to get square with God by performing good works and acts of charity. Since both of these might require spending money, some resourceful church leaders streamlined the process, taking the money and letting the good works slide. A rich sinner could buy “indulgences” to cover adultery, eating meat during Lent, or any number of other transgressions. 

The historical record does not indicate that emitting carbon dioxide was among the redeemable sins. (Well, CO2 wouldn’t be discovered until 1754.) Still, medieval Christians would have recognized the attraction of buying indulgences in the form of carbon offsets rather than actually cutting back on CO2-emitting activities. We can’t help sinning, so if the act of atonement evens the score, why not grant absolution?

Here in the present, a whole industry has sprung up to sell climate indulgences to guilt-ridden liberals. As one website explains soothingly, “Carbon offsets work through supporting tree planting services and carbon offsetting projects to neutralize your emissions and mitigate your impact on the planet.” Buying these indulgences requires just a click of your mouse and a credit card. For $25 you can feel good about an airplane flight of up to 10,000 miles! That’s enough to get you from D.C. to Australia, where you can visit the Great Barrier Reef before it is completely destroyed by the ocean acidification resulting from your carbon emissions. 

(I’ve committed this sin myself: I’ve been to Australia, on a miserably long flight the CO2 emissions of which I did not pay $25 to offset. They hadn’t invented $25 carbon offsets at the time, or I might have.) 

Martin Luther, a 16th century priest who made a name for himself by opposing the selling of indulgences, put the matter succinctly:  “Indulgences are most pernicious,” he wrote, “because they induce complacency and thereby imperil salvation.”  

He meant saving souls, and we mean saving the planet; regardless, he had the psychology right. We’re more likely to excuse ourselves for driving gas-guzzlers and flying to cool places if we also pay to plant trees in Africa or bribe Brazilians not to deforest the Amazon. 

Sadly, that approach doesn’t work. By one calculation, it would require planting at least 200 billion new trees to suck up the excess CO2 emissions of Americans alone. This assumes we don’t lose any trees to fire, drought, disease or clearing. And how’s that working out? As of the end of June, fires had already consumed 20 million acres of Canadian forest this year alone, in large part as a result of climate change. All the carbon those trees had stored up is now back in the atmosphere. 

That doesn’t mean planting trees and saving the rainforest aren’t good works. They are. But there’s a high likelihood any carbon offsets you purchase will be among the 90% of rainforest offsets that a Guardian investigation found were worthless. 

Yet fear not, sinners! Great minds are at work to find effective ways to remove CO2 from the air or the ocean and squirrel it away more or less permanently. Some ideas now in the research or pilot stage involve capturing CO2 from industrial processes like cement manufacturing or from direct-air capture. The CO2 is then injected underground or used as an ingredient in concrete or other products. (Carbon-negative food, anyone?) Technologies that let nature do the heavy lifting include spreading basalt rock dust on farm fields as a soil amendment and using microbes to gobble up CO2 in water.

Getting more attention, likely undeservedly, is the effort to capture and bury CO2 from fossil fuel power plant emissions. This isn’t carbon negative; it simply reduces the amount of CO2 that makes it out of the smokestack. Capturing CO2 where it is most abundant — right where coal and gas are burned — is more efficient than direct-air capture, but it’s expensive and energy-intensive. Shutting the plant and replacing it with renewable energy will almost always be the better option for the planet, and the cheaper one for whoever has to foot the bill. 

Even with generous subsidies in the Inflation Reduction Act (IRA), cost remains the biggest barrier to a market for effective carbon offsets. Carbon capture and sequestration (CCS) projects still can cost upwards of $400 per ton of CO2. In 2021 the U.S. Department of Energy launched what it calls its Carbon Negative Shot, aimed at reducing the price of removing 1 ton of CO2 from the atmosphere to $100 in 1 decade. That would put the price closer to the U.S. Government’s current estimate for the social cost of carbon of $51 per ton, and below the $185 that might be the true cost. 

The market is potentially enormous. Aviation, shipping, steelmaking, chemical manufacturing and cement production are especially challenging to decarbonize. Consider that steelmaking generates about 1.85 tons of CO2 per ton of steel, and the industry produces close to 2 billion tons annually. 

Commercial aviation generated 900 million tons of CO2 in 2019. According to this handy flight calculator, that’s about 2.2 tons of CO2 for every passenger flying round-trip from Virginia’s Dulles Airport to Paris, France. It’s no wonder the voluntary carbon-offset market is expected to become a $250 billion industry by 2050. 

Still, let’s be real. Carbon-negative technology is only needed because we continue to flood the atmosphere with greenhouse gasses from activities we can mostly decarbonize at far less cost today. Money being thrown at expensive CCS or ineffective forest offsets would have a greater impact spent on weatherizing homes, putting solar on rooftops or building renewable energy in fossil fuel-dependent areas. 

In theory, buying renewable energy certificates can do this, too, but their effectiveness is questionable, in part because of the tendency of companies to use them for greenwashing. That is, they want carbon indulgences, but at a price that lets them continue business as usual. 

Medieval sinners would surely relate. 

This article was originally published in the Virginia Mercury on July 19, 2023.

Update: This article in The Guardian challenges the worthiness of pretty much every carbon offset program in existence. Our search for climate indulgences continues.