“If we continue burning coal and oil the way we do today and regret our inaction later, the amounts of greenhouse gas we would need to take out of the atmosphere in order to stabilize the climate would be too huge to manage,” — Lena Boysen from the Potsdam Institute for Climate Impact Research (PIK) in Phys.org.

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When it comes to dealing with global warming and human-forced climate change, the best options for response have always been rapid carbon emissions cuts and an equally rapid energy transition away from fossil fuel burning. And while swiftly transitioning energy systems away from fossil fuel burning, cutting carbon-based consumption, and aggressively increasing energy efficiency may all be seen as difficult or unsavory to the vocal and powerful special interests invested in continued burning of oil, gas, and coal, such cuts and transformations remain the safest path forward.

At issue is the fact that the two other chief climate change response ‘options’ are either inadequate on their own or, worse, can simply amount to so much reckless and harmful flailing about. Atmospheric geo-engineering and rapid removal of carbon from the Earth System — are either costly, difficult to scale to the level needed to remove carbon from the atmosphere fast enough to prevent serious harms under continuing fossil fuel burning, or, in the case of the solar radiation management version of geo-engineering, flat-out dangerous.

(New scientific studies highlight the fact that there is no substitute for a rapid halt to fossil fuel burning when it comes to preventing the worst impacts of human-caused climate change. Image source: The Sierra Club.)

Some of these basic facts were highlighted this week by a new study in the journal Science. The study — Rightsizing Carbon Dioxide Removal — found that under worst-case carbon emissions scenarios, there is practically not enough forested land area to grow the amount of switch grass and other biomass needed to recapture even half of the projected carbon emission. It also found that land mass dedicated to biomass production would need to equal roughly 1/3 of all forested lands under present emissions cuts goals under the Paris Climate Summit in order to prevent 2 C warming. A level of land use that would likely put global food security at risk.

Study Authors Katherine March and Christopher Field note that:

“The models generating possible trajectories of climate change mitigation bet on planetary-scale carbon removal in the second half of the century. For policymakers trying to limit the worst damages from climate change, that bet is reckless. This puts climate change mitigation, global food security and biodiversity protection on a collision course with no easy off-ramps.”

Only the most ambitious cuts to emissions combined with a moderate assist through considerable advances in atmospheric carbon capture provide a reasonable path to avoiding 2 C warming, according to the study.

A separate but similar study also published in May provides some confirmation to the Stanford study’s results. The co-author of that study, entitled The Limits to Global Warming Mitigation by Terrestrial Carbon Removal,Wolfgang Lucht from PIK notes in Phys.org:

“As scientists we are looking at all possible futures, not just the positive ones. What happens in the worst case, a widespread disruption and failure of mitigation policies? Would plants allow us to still stabilize climate in emergency mode? The answer is: no. There is no alternative for successful mitigation [cutting carbon emissions]. In that scenario plants can potentially play a limited, but important role, if managed well. [Emphasis Added]”

The issue is the fact that while methods like planting trees, changing the way we manage farmland, or even adding various carbon capturing biofuel plants and enhanced weathering materials to capture more carbon from the air is likely only capable of drawing down a fraction of the carbon we presently emit each year (and an even smaller fraction of carbon if emissions keep growing). At best, under practical considerations, we might be able to take down 1-3 billion tons of carbon every year compared to a present emission in excess of 10 billion tons and a BAU emission that could hit 20 billion tons of carbon per year or more.

(This graphic, produced by Greenpeace, provides a good illustration of basic carbon math. However, given the fact that warming will tend to push more carbon into the atmosphere from the Earth System and keep it there for a longer period, it’s likely that some assist by enhanced atmospheric carbon capture will be necessary even if carbon emissions are rapidly cut to zero. That said, atmospheric carbon capture at best provides an avenue for moderately enhancing atmospheric carbon draw-down. New studies warn that atmospheric carbon capture by itself and without coordinate rapid cuts to fossil fuel burning is not a practical solution. Image source: Greenpeace.)

Such levels of carbon capture, even if they were achieved in as short a time as two decades, would not be enough to prevent 2 C warming under anything but the most modest future emissions pathways. As a result, the primary climate change response strategy should continue to focus on increasing and rapidly scaling the size of planned emissions cuts. Meanwhile, atmospheric carbon capture is a good potential option as a follow-on to rapid emissions cuts to zero as soon as possible — providing a means eventually, over many decades, to possibly start to claw atmospheric greenhouse gases down from very dangerous and harmful levels. But such an option alone should not be viewed as something that will magically swoop in to save us from climate destruction if we continue to burn fossil fuels willy-nilly.

Chris Field — professor of biology & Earth System science and director of the Stanford Woods Institute for the Environment provides this urgent observation following his study’s publication:

“For any temperature limit, we’ve got a finite budget of how much heat-trapping gases we can put into the atmosphere. Relying on big future deployments of carbon removal technologies is like eating lots of dessert today, with great hopes for liposuction tomorrow.”

With the caveat being that eating lots of dessert today is likely to have far more limited and less disastrous consequences than continuing to burn oil, gas and coal.

Links:

Rightsizing Carbon Dioxide Removal

The Limits to Global Warming Mitigation by Terrestrial Carbon Removal

Assuming Easy Carbon Removal is High-Stakes Gamble

Planting Trees Cannot Replace Carbon Emissions Cuts