The UN climate report is pinning hopes on carbon removal technologies that barely exist


In this model almost all carbon removal comes through a process known as bioenergy with carbon capture and storageor BECCS. Basically, this requires the cultivation of crops that absorb CO2 and then use the harvested biomass to produce heat, electricity or fuel, capturing and storing any emissions. But despite the billions and billions of tons of carbon removal that climate models count on through BECCS, so far this has only been done in small projects.

Other technical approaches are also immature, including carbon suction machines and various ways to accelerate the natural processes by which minerals i oceans collect and dispose of CO2. It is proven challenging develop systems to reliably encourage and measure carbon sequestration through natural systems such as forests and soil also.

The IPCC assessment on Monday noted a number of other limitations and difficulties.

First, although carbon sequestration reduces the level of greenhouse gases in the atmosphere, the report notes that this effect can be offset to some extent. Modeling studies they found that the oceans and land begin to release more CO2 in response to this change in atmospheric chemistry over time, undermining the benefits.

In addition, while removing carbon could gradually mitigate rising temperatures and acidifying the oceans, it magically doesn’t undo all climate influences. Significantly, it will take centuries for the oceans to return to the level around which we built cities on the coast, the report emphasizes. There could be irreversible damage to ice sheets, coral reefs, rainforests and certain species, depending on how much warmer the world will become before the world reduces emissions and increases carbon sequestration.

Chapter five This report outlines a number of other trade-offs and unknowns with almost all potential approaches to widespread carbon sequestration.

Carbon extraction machines require large amounts of energy and materials. Planting more trees for carbon sequestration or fuel crops will compete with growing food for a growing world population.

Climate change alone will jeopardize the ability of forests to absorb and store carbon dioxide, as the risk of drought, fire and insect infestation increases with increasing temperature. There is still considerable scientific uncertainty regarding the side effects of different approaches to ocean-based marine ecosystems.

The good news is that there are different ways to remove carbon from the air, and a growing number of research groups and companies are working to develop better and cheaper methods. But as Monday’s report makes clear, we are far behind in the race with very high stakes.

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