The UN report found that greenhouse gases are likely to push global temperatures at least 1.5 ° C above pre-industrial conditions over the next 20 years, leading to more frequent and violent heat waves, floods and droughts. When that happens, removing carbon is essentially the only way to bring the climate back to a safer zone, as the greenhouse gas lingers in the atmosphere for hundreds to thousands of years. (One last alternative is maybe some form of geoengineering the heat is reflecting back into space, but this controversial idea raises all sorts of concerns.)
The model used to create the most optimistic scenario in the report, which limits warming to 1.5 ° C, he believes the world will find ways to remove about 5 billion tons of carbon dioxide a year by mid-century and 17 billion tons of carbon dioxide a year by 2100. (The scenario is known as SSP1-1.9, and these numbers are based on an analysis of previous dates by Zeke Hausfather, climate scientist at the Breakthrough Institute and contributing author to the UN assessment.)
That requires the expansion of technologies and techniques that can pull as much CO2 out of the atmosphere each year as the US economy emitted in 2020. In other words, the world would have to build a brand new carbon scavenging sector based on the emissions benchmark of all American automobiles, power plants, planes, and factories over the next 30 years or so.
We could remove fewer, but only if we cut emissions even faster, come to terms with greater climate risks – or both.
In the above model, almost all of the carbon removal is achieved through an “artificial” approach called the. is known Bioenergy with CO2 capture and storage, or BECCS. Essentially, it requires the cultivation of plants that consume CO2 and the subsequent use of the harvested biomass to generate heat, electricity or fuels, as well as the collection and storage of the emissions that arise. But despite the billions and billions of tons of carbon removal that climate models rely on by BECCS, this has so far only been done in small projects.
The smaller residual removal in the model is done through “natural” solutions such as reforestation and tree planting (see figure below).
We know forests, soils, bogs, and other natural systems absorb significant amounts of carbon dioxide, but it does turned out to be challenging To develop markets and systems that reliably set, measure and verify incentives. Other technical approaches are now immature, including carbon-sucking machines and various methods of speeding up the processes with which Minerals and the oceans Absorb and store CO2.
The IPCC assessment identified numerous other limitations and difficulties.
While carbon removal reduces the amount of greenhouse gases in the atmosphere, the report notes that this effect can be offset to some extent. Modeling studies have found that the oceans and land in response to these changing atmospheric chemistry release more CO2 over certain periods of time, undermining the benefits.
In addition, while carbon removal could gradually mitigate ocean temperature rise and acidification, it might not magically reverse all climate impacts. In particular, it would take centuries to bring the oceans back to the level at which we built our coastal cities, the report stresses. Ice sheets, coral reefs, rainforests and certain species could be damaged almost irreversibly, depending on how much warmer the world gets, before we deeply cut emissions and increase carbon depletion.