We need to sequester carbon – not just stop emitting it

But decarbonisation has become a touchy subject. There are real concerns that the increasing focus on reducing greenhouse gas emissions could encourage governments and companies to delay or even avoid the most obvious and direct way to address climate change: preventing emissions from entering the atmosphere in the first place.

The convenient perception that we could continue pumping out large levels of carbon dioxide and simply clean up the atmosphere in the future is an example of what is known as “moral hazard.” It risks the continued use of fossil fuels and shifting the costs of dealing with climate change to future generations.

This is a valid concern. Some companies have wrongly suggested that decarbonisation could allow us to continue emitting at nearly half of current global levels. But that would require capturing and storing carbon dioxide at levels that are almost certainly technically, environmentally, or economically unfeasible, or possibly all of the above.

However, there is also a real risk that stigmatizing carbon removal because of moral hazard concerns creates an even greater danger: delaying much-needed investment and jeopardizing our ability to meet future climate goals. Unfortunately, after decades of delay, there are now simply few paths to achieving our climate goals that don’t require cutting emissions today and building the capacity to suck up huge amounts of carbon dioxide in the decades to come.

Reducing emissions is not enough

Why is carbon removal necessary at all, and why can’t we simply stop climate change by achieving “absolute zero” emissions? A recent UN report identifies four distinct roles for carbon removal in climate modeling scenarios that limit warming to well below 2˚C above pre-industrial levels by 2100.

First, while fossil fuels can be replaced by clean energy alternatives in much of the economy, there will be some ongoing carbon dioxide emissions from sectors that are difficult to fully decarbonize. These are major industries, such as aviation, cement and steel, where we simply do not have affordable, scalable, carbon-free technologies. Although more work is needed to understand how low carbon dioxide emissions can be, such sectors are likely to continue to produce several billion tons per year that need to be neutralized by carbon removal.

Second, carbon dioxide is not the only greenhouse gas warming the planet. Others, including methane and nitrous oxide from sources such as livestock, animal waste and fertilizer use, are much more difficult to eliminate entirely.

A recent UN report found that available technologies could probably reduce emissions of these gases by around 50%, with additional behavioral changes, such as dietary changes, pushing that to 66%. However, carbon removal would have to balance the significant remaining amount.

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