In Brief...
Atmospheric CO₂ levels are currently at their highest in millions of years, largely due to centuries of industrialization and significant land-use changes. These human activities have disrupted the Earth's natural carbon balance, leading to increased greenhouse gas concentrations and global temperature rises. Scientists warn that this warming could lead to profound climate changes, including rising sea levels as polar ice melts.
Avoiding the most extreme effects of global warming means reducing emissions from industry and transport, as well as ceasing the unsustainable management of land and forests which can lead to the release of billions of tonnes of CO2 every year.
Decarbonizing means not only transitioning from the burning of fossil fuels to the use of clean energy, but also preventing the release of CO2 from industries which do not have obvious pathways to cutting back emissions. In addition, it will require the advancing and deplying technologies that actively remove CO2 from the atmosphere, using a combination of engineered approaches and nature-based solutions.
Carbon Capture and Storage (CCS) technologies aim to target the emissions from industries which are otherwise hard to decarbonize, capturing CO2 before it reaches the atmosphere and then securely storing it deep underground.
Meanwhile, Carbon Dioxide Removal (CDR) encompasses a variety of methods - some enhancing natural processes, others relying on engineered solutions - that remove CO2 from the atmosphere and sequester it in natural carbon sinks, where, depending on the method of CDR used. it can remain stored for anywhere from decades to millions of years.
While all methods of CCS and CDR can in theory help to have some effect on managing atmospheric CO2 levels, the challenge in all cases will be scaling them to levels that can have a significant impact.
- Atmospheric CO₂ levels have risen by 50% due to human activities, intensifying global warming and necessitating urgent climate action.
- The Paris Agreement, signed by 196 countries at the COP21 climate summit in 2015, aims to limit global warming to well below 2°C, preferably 1.5°C, compared to pre-industrial levels.
- Many countries plan to meet their Paris commitments by setting targets for achieving net-zero emissions, where CO₂ emissions are balanced by removal.
- While decarbonization is vital across all sectors, some emissions will remain unavoidable, requiring additional solutions.
- Carbon Capture and Storage (CCS), removing CO2 from emissions and permanently storing it underground, is one solution for ‘hard-to-abate’ industries such as cement production.
- Carbon Dioxide Removal (CDR), pulling CO2 out of the air, will be necessary to offset unavoidable emissions and address historical CO₂ accumulation in the atmosphere.
- Engineered CDR solutions include Direct Air Capture (DAC), which extracts CO₂ directly from the air for permanent underground storage or conversion to other materials.
- Natural CDR solutions include accelerating nature’s processes such as forestation, Enhanced Rock Weathering (ERW), and biochar, all of which result in the storage of carbon in natural sinks such as trees, soil and carbonate rock minerals.
- Bioenergy with Carbon Capture and Storage (BECCS) is a combination of natural and engineering solutions, growing biomass which pulls CO2 from the air as it grows, and then burning it to produce energy while capturing the CO₂ produced during combustion, potentially achieving negative emissions.
- Although these methods are based on well-understood principles, the key challenge is scaling CCS and CDR to levels that significantly reduce atmospheric CO₂, requiring the removal of vast amounts annually.
How the Greenhouse Effect Works
When solar energy reaches Earth's surface, it is absorbed and then re-emitted as infrared radiation. Unlike nitrogen and oxygen, which between them form over 99% of the Earth’s atmosphere and do not absorb this infrared energy, greenhouse gas molecules trap some of this energy, re-emitting it and warming the surrounding air and the Earth’s surface.
Carbon Cycles: Short-Term and Long-Term
Over millions of years, CO₂ levels have fluctuated, forcing life to adapt to changing conditions.
Atmospheric CO₂ is regulated through both short- and long-term carbon cycles:
- The short-term carbon cycle operates over decades to centuries, cycling carbon between the atmosphere, living organisms, and the ocean. Key processes include photosynthesis (where plants convert CO₂ into energy and organic material), respiration (where organisms break down food and release CO₂), and decomposition. The exchange of gases between ocean surfaces and the atmosphere also plays a crucial role.
- Meanwhile, the long-term carbon cycle unfolds over geological time periods. Atmospheric CO2 dissolved in rain to form a weak acid will react with silicate rocks, eventually leading to the formation of carbonate rock minerals. The carbon is then locked away for millions of years before being released as CO2 as a result of volcanic activity.
While the Earth itself would eventually adjust to these changes, our current way of life depends on climate stability. Coastal cities are built on the assumption that sea levels remain stable, and our agricultural systems rely on predictable weather patterns.
Over the past 25 years, the shift from fossil fuels to renewable energy sources like wind and solar has accelerated, significantly reducing emissions. But what about sectors that are harder to decarbonize, such as transportation and some heavy industries? And what of the legacy emissions from centuries of industrialization that still linger in the atmosphere?
Can we harness the same ingenuity used to extract fossil fuels from some of the planet’s most challenging environments, not only to drastically reduce CO₂ emissions but also to remove CO₂ from the atmosphere?
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Key CommitmentsThe signing of the Paris Agreement in 2015 was a landmark moment in global climate action, marking a shared recognition that:
- The hundreds of billions of tonnes of CO₂ emitted since the Industrial Revolution are driving climate change, with potentially catastrophic consequences.
- Nations must act decisively to reduce these emissions.
Global Temperature Goals
The agreement acknowledged that action was required from all countries, including traditional CO₂ emitters like Europe and North America and rapidly growing economies in Asia.
By signing the agreement, countries committed to Nationally Determined Contributions (NDCs)—policy measures aimed at reducing greenhouse gas emissions in key sectors like power generation, transportation, and heavy industry (e.g., steel, cement, and chemicals).
The agreement's primary goal was to limit global warming to below 2°C, preferably 1.5°C, to avoid triggering climate tipping points that could lead to more frequent droughts, extreme weather, ecosystem damage, and coastal inundation.
In the years following the signing of the Paris Agreement, scientists began to point out that the commitments made by countries, even if all acted upon, would not be enough to prevent global temperature increasing above 2 degrees by mid-century. As countries began to accept the harsh reality that promises made in Paris did not go far enough, some began to set more ambitious climate policies.
Global Progress and Challenges
The United Kingdom and the European Union have since set legally binding targets to achieve net-zero emissions by 2050, with the UK's Climate Change Act and the EU's European Green Deal demonstrating an intention to follow through with more stringent climate action. In the United States, the Biden administration re-joined the Paris Agreement, set a goal of achieving net-zero emissions by 2050, and passed the Inflation Reduction Act of 2022, providing significant investments in clean energy and climate mitigation.
China has pledged to achieve carbon neutrality by 2060 and peak its emissions before 2030. The country's 14th Five-Year Plan (2021-2025) emphasizes green development and low-carbon technologies, indicating a shift towards more aggressive climate action.
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The IEA’s Net Zero ReportThe International Energy Agency's (IEA) ground-breaking report "Net Zero by 2050: A Roadmap for the Global Energy Sector" was released in May 2021, with the aim of clarifying the implications of different strategies for reaching net-zero targets by mid-century. The roadmap included multiple scenarios, each based on different rates of transition from fossil fuels to renewable energy as well as advancements in green technologies.
The Limits of Decarbonization
The report also highlights that completely decarbonizing all industries was simply not possible. Many industries, such as cement manufacturing, produce CO2 due to the inherent chemical processes which take place, so even using renewable energy instead of coal to heat cement kilns would not eliminate all emissions. And while the roadmap noted a significant decline in coal usage to generate electricity, it also points out that many countries will continue to rely on coal in the near term due to the lack of immediate alternatives for providing sufficient, on-demand electricity to power their economies. In addition, it acknowledged that other industries such as aviation currently have no alternative but to continue burning fossil fuels to keep planes in the air, at least until biofuels are developed that can do the job.
According to the IEA report, the key solution is to transition away from fossil fuels as quickly as possible. However, for sectors where emissions reductions are challenging or technically unfeasible - often referred to as the "hard-to-abate" sectors - carbon capture and storage (CCS) offers a viable, albeit currently expensive, solution. This technology captures CO2 from industrial plant emissions, then transports it to long-term storage sites deep underground, preventing it from entering the atmosphere. Although this may sound impractical given the volume of CO2 involved, the technologies for isolating CO2 from flue gases of industrial plants is actually very mature. Since the 1970s, carbon capture has been in operation at natural gas processing plants in the US, with the captured CO2 being used for enhanced oil recovery (EOR) in oil fields. In this process, CO2 is pumped into oil fields to displace stubborn reserves of oil. Finding permanent storage for billions of tonnes of CO2 may seem impossible, but certain underground locations are well-suited. These include porous rock formations that can absorb CO2 and depleted oil and gas fields sealed by impermeable rock layers. Carbon dioxide in the atmosphere does not break down naturally, meaning that the CO2 we have emitted across several centuries and which has not been absorbed by natural sinks like oceans and forests, is still present and contributing to climate change. Therefore, beyond reducing new emissions, we must also address the existing build-up of atmospheric CO₂.
To address this accumulated CO2, there are two fundamental approaches: boost nature's CO2 removal methods or employ engineered solutions to directly extract CO2 from the air. Natural carbon dioxide removal (CDR) methods aim to accelerate processes in the Earth's natural carbon cycles, including the planting of trees in new or existing forests - afforestation and reforestation - so that the carbon in the CO2 absorbed by trees is stored in the forests’ biomass and soils.
Another natural approach is the method of enhanced rock weathering, which accelerates the natural process where CO2 dissolved in rainwater reacts with certain rock types to form solid carbonates, effectively locking away the carbon for millions of years. On the engineered side, direct air capture (DAC) technologies are being developed to literally suck CO2 out of the atmosphere. Once captured, the CO2 is compressed and pumped deep underground for permanent storage, similar to CCS.
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Strategies for Gigatonne-Scale CO2 Reduction and RemovalTo combat climate change effectively, CO₂ reduction will have to reach gigatonne-scale annually. Continued efforts to Decarbonize the power, industry, and transportation will be essential, but it will not be enough on its own. Legacy emissions—CO₂ already in the atmosphere from past industrial activity—must be removed, while future unavoidable emissions from sectors like aviation, cement, and agriculture will persist due to the lack of zero-carbon alternatives.
Drastic emissions cuts alone will not be sufficient—large-scale CO₂ removal is also required. Achieving this will demand a combination of approaches, including:
- Large-scale reforestation and afforestation programs
- Enhanced weathering techniques, such as distributing crushed rock dust over large areas of land
- Widespread deployment of carbon capture technologies at industrial facilities
- Development and implementation of methods for long-term geological storage of captured CO2
- Advancement and scaling of direct air capture technologies to remove CO2 already present in the atmosphere
Future Research and Development
As these relatively new fields of CO2 capture and removal continue to evolve, including innovative solutions we may not yet even have imagined, only continued research and extensive global pilot projects will determine the role each can realistically play in effectively and sustainably helping to control CO2 levels.
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As developments unfold in the realm of carbon capture, storage, and removal technologies, they will be increasingly documented across various media - from scholarly articles and research papers to podcasts and videos. The rapidly evolving nature of this field means there will be a constant stream of new information, breakthroughs, and discussions. This website will aim to act as a hub, following diverse sources to provide our audience with a comprehensive, up-to-date overview of the latest advancements, challenges, and debates in this advancing area of climate action. In the next section, we will examine two key approaches in more detail - carbon capture and storage (CCS) and carbon dioxide removal (CDR) - exploring their methods, potential impacts, and the obstacles to implementing them at the necessary scale.
Overview 
