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Carbon Dioxide Removal (CDR) primarily focuses on preventing new CO2 emissions from industrial sources.
Answer: False
Explanation: Carbon Dioxide Removal (CDR) is defined as the deliberate human activity of removing existing CO2 from the atmosphere, distinct from Carbon Capture and Storage (CCS), which prevents new emissions from industrial sources.
The IPCC's definition of CDR includes natural CO2 uptake that is not directly caused by human activities.
Answer: False
Explanation: The IPCC's formal definition of Carbon Dioxide Removal (CDR) explicitly excludes natural CO2 uptake that is not directly caused by human activities, focusing instead on anthropogenic efforts.
Integrated Assessment Models (IAMs) have played a minor role in shaping the global policy agenda for negative emissions.
Answer: False
Explanation: Integrated Assessment Models (IAMs) have played a fundamental and crucial role in shaping the global policy agenda for negative emissions, particularly within the Intergovernmental Panel on Climate Change (IPCC).
The Earth's surface temperature will stabilize once global emissions are reduced to net zero, requiring both emission cuts and CDR.
Answer: True
Explanation: Stabilizing the Earth's surface temperature necessitates reducing global emissions to net zero, a goal that requires both aggressive emission reductions and the strategic deployment of Carbon Dioxide Removal (CDR) technologies.
Carbon Dioxide Removal (CDR) is defined as any natural process that removes CO2 from the atmosphere.
Answer: False
Explanation: Carbon Dioxide Removal (CDR) is specifically defined as deliberate human activities that remove CO2 from the atmosphere, and the IPCC explicitly excludes natural CO2 uptake not directly caused by human intervention from this definition.
Emissions from agriculture, aviation, and certain industrial processes are particularly challenging to eliminate, making CDR necessary to achieve net-zero.
Answer: True
Explanation: Emissions from sectors such as agriculture (nitrous oxide), aviation, and specific industrial processes are inherently difficult to abate, making Carbon Dioxide Removal (CDR) an indispensable component for achieving global net-zero emissions targets.
The primary distinction between Carbon Dioxide Removal (CDR) and Carbon Capture and Storage (CCS) is that CDR removes existing atmospheric CO2, while CCS prevents new emissions from industrial facilities.
Answer: True
Explanation: The fundamental distinction between Carbon Dioxide Removal (CDR) and Carbon Capture and Storage (CCS) lies in their targets: CDR actively removes CO2 already present in the atmosphere, whereas CCS intercepts and stores CO2 emissions directly from industrial sources before they enter the atmosphere.
Which statement accurately defines Carbon Dioxide Removal (CDR)?
Answer: It involves deliberate human activities that remove CO2 from the atmosphere and store it durably in various reservoirs or products.
Explanation: Carbon Dioxide Removal (CDR) is precisely defined as deliberate human activities that extract CO2 from the atmosphere and ensure its durable storage in geological, terrestrial, or ocean reservoirs, or within various products.
Which of the following is NOT an alternative term used to describe Carbon Dioxide Removal (CDR)?
Answer: Carbon Capture and Storage (CCS)
Explanation: While 'carbon removal,' 'greenhouse gas removal (GGR),' and 'negative emissions' are alternative terms for Carbon Dioxide Removal (CDR), Carbon Capture and Storage (CCS) is a distinct process focused on preventing new emissions from industrial sources, not removing existing atmospheric CO2.
Why is CDR increasingly integrated into climate policy?
Answer: It is recognized as essential for achieving net-zero emissions by complementing emission reductions.
Explanation: Carbon Dioxide Removal (CDR) is increasingly integrated into climate policy because it is recognized as an essential complement to emission reductions, indispensable for achieving the ambitious targets of net-zero emissions by counterbalancing hard-to-abate sources.
According to the IPCC, what is explicitly excluded from the formal definition of Carbon Dioxide Removal (CDR)?
Answer: Natural CO2 uptake not directly caused by human activities.
Explanation: The IPCC's formal definition of Carbon Dioxide Removal (CDR) explicitly excludes natural CO2 uptake that is not directly caused by human activities, emphasizing the anthropogenic nature of CDR efforts.
Land-based biological methods, such as afforestation/reforestation and BECCS, are identified as having the greatest potential for climate change mitigation in illustrative pathways.
Answer: True
Explanation: Illustrative mitigation pathways indicate that land-based biological methods, including afforestation/reforestation and Bioenergy with Carbon Capture and Storage (BECCS), possess the greatest potential for contributing to climate change mitigation.
Biochar is produced by heating biomass at high temperatures in an oxygen-rich environment.
Answer: False
Explanation: Biochar is produced through pyrolysis, a process that involves heating biomass at high temperatures in an environment with low oxygen levels, not an oxygen-rich one.
Carbon farming aims to increase soil organic carbon content, which can improve soil water retention and reduce the need for synthetic fertilizers.
Answer: True
Explanation: Carbon farming aims to increase soil organic carbon content, which offers benefits such as enhanced plant growth, improved soil water retention capacity, and a reduced reliance on synthetic fertilizers.
Bioenergy with Carbon Capture and Storage (BECCS) aims to achieve net negative emissions by extracting bioenergy and capturing the CO2 produced during energy generation.
Answer: True
Explanation: Bioenergy with Carbon Capture and Storage (BECCS) is designed to achieve net negative emissions by combining bioenergy extraction from biomass with the capture and storage of the CO2 generated during the energy production process.
Forests typically reach their maximum carbon sequestration rate immediately after planting.
Answer: False
Explanation: Forests typically require approximately 10 years after planting to reach their maximum carbon sequestration rate, rather than achieving it immediately.
BiCRS technologies primarily remove CO2 from the atmosphere using human-engineered chemical processes.
Answer: False
Explanation: Biomass Carbon Removal and Storage (BiCRS) technologies primarily leverage the natural process of photosynthesis by plants to remove CO2 from the atmosphere, rather than relying on human-engineered chemical processes for direct air extraction.
Which of the following CDR methods is categorized as a land-based biological approach?
Answer: Afforestation
Explanation: Among the listed options, afforestation is categorized as a land-based biological approach to Carbon Dioxide Removal (CDR), involving the planting of new forests to absorb atmospheric CO2.
What is the process of establishing a forest in an area where there was previously no forest called?
Answer: Afforestation
Explanation: The process of establishing a forest in an area where no forest previously existed is termed afforestation, a key land-based method for carbon removal.
How long does it typically take for forests to reach their maximum carbon sequestration rate after planting?
Answer: Approximately 10 years
Explanation: Forests typically require approximately 10 years after planting to reach their maximum carbon sequestration rate, a period crucial for establishing their full carbon-absorbing capacity.
How do Biomass Carbon Removal and Storage (BiCRS) technologies primarily remove CO2 from the atmosphere?
Answer: By leveraging the natural process of photosynthesis by plants.
Explanation: Biomass Carbon Removal and Storage (BiCRS) technologies primarily remove CO2 from the atmosphere by leveraging the natural process of photosynthesis in plants, followed by engineered solutions for carbon sequestration from the biomass.
Ocean fertilization is a marine CDR method estimated to sequester carbon for thousands of years.
Answer: False
Explanation: Ocean fertilization, a marine Carbon Dioxide Removal (CDR) method, is estimated to sequester carbon for a relatively short duration of 10 to 100 years, not thousands of years.
Ocean alkalinity enhancement involves introducing plant nutrients into the upper ocean to stimulate phytoplankton growth.
Answer: False
Explanation: Ocean alkalinity enhancement involves grinding and dispersing minerals into the ocean to precipitate carbonate, whereas introducing plant nutrients to stimulate phytoplankton growth is characteristic of ocean fertilization.
Electrochemical techniques for marine CDR are always expensive, even when integrated with other seawater processing operations.
Answer: False
Explanation: While electrochemical techniques for marine Carbon Dioxide Removal (CDR) can be expensive in isolation, their cost can be significantly reduced when integrated with other seawater processing operations, such as desalination, with potential for cost offsetting through byproduct sales.
What is the estimated carbon sequestration duration for ocean fertilization?
Answer: 10–100 years
Explanation: Ocean fertilization, a marine Carbon Dioxide Removal (CDR) method, is estimated to sequester carbon for a relatively short duration, typically ranging from 10 to 100 years.
How can the cost of electrochemical techniques for marine CDR be optimized?
Answer: By integrating them with seawater processing operations like desalination.
Explanation: The cost of electrochemical techniques for marine Carbon Dioxide Removal (CDR) can be significantly optimized by integrating them with existing seawater processing operations, such as desalination, potentially offsetting carbon removal costs through byproduct sales.
Direct Air Capture (DAC) plants require significantly more land area to capture 1 MtCO2 per year compared to planting an equivalent number of trees.
Answer: False
Explanation: A Direct Air Capture (DAC) plant capable of capturing 1 MtCO2 per year requires a significantly smaller land area (0.4–1.5 km²) compared to planting an equivalent number of trees (3,098–4,647 km²).
Converting CO2 into insoluble carbonate salts is a method for more permanent storage in the Earth's crust.
Answer: True
Explanation: One method for achieving more permanent storage of carbon dioxide in the Earth's crust involves converting it into insoluble carbonate salts, alongside direct injection into subsurface geological formations.
How can carbon dioxide be stored more permanently in the Earth's crust?
Answer: By converting it into insoluble carbonate salts or injecting it into the subsurface.
Explanation: Carbon dioxide can be stored more permanently in the Earth's crust through methods such as injecting it into subsurface geological formations or converting it into stable, insoluble carbonate salts.
What is Direct Air Capture with Carbon Sequestration (DACCS)?
Answer: A process that employs chemical or physical methods to extract CO2 directly from ambient air for long-term storage.
Explanation: Direct Air Capture with Carbon Sequestration (DACCS) is a process that utilizes chemical or physical methods to extract carbon dioxide directly from the ambient air, followed by its sequestration in safe, long-term storage.
How does the land footprint of a DAC plant compare to tree planting for equivalent CO2 capture?
Answer: A DAC plant requires significantly less land.
Explanation: For equivalent CO2 capture, a Direct Air Capture (DAC) plant requires a significantly smaller land footprint (0.4–1.5 km² per MtCO2/year) compared to the extensive land area needed for tree planting (3,098–4,647 km²).
The Oxford Principles for Net Zero Aligned Carbon Offsetting recommend that organizations prioritize carbon reduction offsets over carbon removal offsets until mid-century.
Answer: False
Explanation: The Oxford Principles for Net Zero Aligned Carbon Offsetting advocate for organizations to gradually increase their procurement of carbon removal offsets, with the ultimate goal of exclusively sourcing carbon removals by mid-century, rather than prioritizing reduction offsets until then.
Biochar commands a higher price in the carbon removal market than nature-based solutions because it offers a more durable carbon sink.
Answer: True
Explanation: Biochar commands a higher price in the carbon removal market compared to nature-based solutions because it provides a more durable carbon sink, capable of sequestering carbon for hundreds or thousands of years, in contrast to the more volatile nature of biological storage.
As of 2021, CDR is fully covered by the EU Allowance and UK Emissions Trading Scheme.
Answer: False
Explanation: As of 2021, Carbon Dioxide Removal (CDR) is not yet fully covered by the EU Allowance or the UK Emissions Trading Scheme, though the European Commission is actively preparing for carbon removal certification.
Financing for high-tech CDR methods has primarily come from government support, with limited private sector involvement as of early 2023.
Answer: False
Explanation: As of early 2023, the substantial increase in financing for high-tech Carbon Dioxide Removal (CDR) methods has primarily originated from voluntary private sector initiatives, with government support also growing but not being the predominant source.
A concern regarding CDR funding is that voluntary private sector markets have historically been much smaller than government-driven markets.
Answer: True
Explanation: A significant concern regarding Carbon Dioxide Removal (CDR) funding is the historical disparity in scale between voluntary private sector markets and government-driven markets, with the former being orders of magnitude smaller, potentially limiting the necessary scaling of CDR technologies.
Why does biochar command a higher price in the carbon removal market compared to nature-based solutions?
Answer: It offers a more durable carbon sink, lasting hundreds or thousands of years.
Explanation: Biochar commands a higher price in the carbon removal market than nature-based solutions primarily because it offers a more durable carbon sink, capable of sequestering carbon for hundreds or even thousands of years, in contrast to the inherent volatility of biological storage.
What do the Oxford Principles for Net Zero Aligned Carbon Offsetting recommend for organizations by mid-century?
Answer: To exclusively source carbon removal offsets.
Explanation: The Oxford Principles for Net Zero Aligned Carbon Offsetting recommend that organizations progressively increase their reliance on carbon removal offsets, with the ultimate objective of exclusively sourcing such offsets by mid-century to align with global climate goals.
As of 2021, what is the status of CDR in the EU Emissions Trading Scheme (ETS)?
Answer: The European Commission is preparing for carbon removal certification, but it's not yet covered.
Explanation: As of 2021, Carbon Dioxide Removal (CDR) is not yet covered by the EU Allowance within the EU Emissions Trading Scheme (ETS); however, the European Commission is actively developing a framework for carbon removal certification.
What has been the primary source of the substantial increase in financing for high-tech CDR methods as of early 2023?
Answer: Voluntary private sector initiatives.
Explanation: As of early 2023, the substantial increase in financing for high-tech Carbon Dioxide Removal (CDR) methods has predominantly stemmed from voluntary private sector initiatives, complemented by growing government support.
The 'moral hazard' associated with CDR refers to the risk that its future deployment could reduce current efforts to mitigate climate change.
Answer: True
Explanation: The 'moral hazard' associated with Carbon Dioxide Removal (CDR) refers to the concern that the prospect of future large-scale deployment could inadvertently lead to a reduction in immediate efforts to mitigate climate change.
Biological carbon stores like forests are considered highly stable and guaranteed long-term carbon sinks due to their natural resilience.
Answer: False
Explanation: Biological carbon stores, such as forests, are considered 'volatile' carbon sinks because their long-term sequestration cannot be guaranteed due to risks from natural events like wildfires and disease, as well as economic or political pressures.
The 2019 NASEM report supported delaying mitigation efforts, anticipating that Negative Emissions Technologies (NETs) would provide a reliable backstop.
Answer: False
Explanation: The 2019 NASEM report explicitly concluded that any argument to delay mitigation efforts in anticipation of Negative Emissions Technologies (NETs) drastically misrepresents their current capacities and the likely pace of research progress, underscoring the urgency of immediate emission reductions.
While methane removal has been suggested, nitrous oxide is considered a more suitable subject for removal research due to its significantly longer atmospheric lifetime.
Answer: True
Explanation: Researchers suggest that nitrous oxide, rather than methane, may be a more suitable subject for greenhouse gas removal research due to its significantly longer atmospheric lifetime, which implies a more persistent warming effect.
A disadvantage of carbon farming is the potential for increased land clearing and promotion of monocultures, negatively impacting ecosystem services.
Answer: True
Explanation: Potential disadvantages of carbon farming include the risk of increased land clearing, the promotion of monocultures, and a subsequent loss of biodiversity, all of which can negatively impact ecosystem services.
What is the primary criticism leveled against Carbon Dioxide Removal (CDR) efforts by oceanographer David Ho in 2023?
Answer: CDR must not be regarded as a substitute for required cuts in greenhouse gas emissions.
Explanation: Oceanographer David Ho's primary criticism of Carbon Dioxide Removal (CDR) efforts in 2023 was that CDR should not be considered a substitute for the immediate and radical reductions required in greenhouse gas emissions.
What was identified as a 'major risk' for achieving climate goals in 2018 regarding heavy reliance on large-scale CDR deployment?
Answer: Uncertainties regarding how quickly CDR technologies could be deployed at the necessary scale.
Explanation: In 2018, a 'major risk' for achieving climate goals, particularly limiting warming to 1.5°C, was identified as the uncertainties surrounding the speed at which Carbon Dioxide Removal (CDR) technologies could be deployed at the necessary scale.
What is the 'moral hazard' associated with the prospect of large-scale future CDR deployment?
Answer: It could potentially lead to a reduction in near-term efforts to mitigate climate change.
Explanation: The 'moral hazard' associated with the prospect of large-scale future Carbon Dioxide Removal (CDR) deployment is the potential for it to diminish near-term efforts to mitigate climate change, based on an implicit assumption of future technological solutions.
What did the 2019 NASEM report conclude regarding delaying mitigation efforts in anticipation of Negative Emissions Technologies (NETs)?
Answer: It drastically misrepresents their current capacities and the likely pace of research progress.
Explanation: The 2019 NASEM report concluded that any argument to delay mitigation efforts based on the anticipation of Negative Emissions Technologies (NETs) drastically misrepresents their current capacities and the likely pace of research progress, emphasizing the need for immediate action.
What is a significant social and ecological limitation identified for carbon dioxide removal?
Answer: The extensive land area required, potentially competing with agriculture.
Explanation: A significant social and ecological limitation identified for carbon dioxide removal is the extensive land area required for many methods, which can lead to competition with other land uses, such as agriculture, impacting food security and ecosystems.
Why are biological carbon stores like forests considered 'volatile' carbon sinks?
Answer: Their long-term sequestration cannot be guaranteed due to natural events or changing priorities.
Explanation: Biological carbon stores such as forests are deemed 'volatile' carbon sinks because their long-term sequestration is not guaranteed, being susceptible to carbon release due to natural disturbances like wildfires, disease, or shifts in economic and political priorities.
Which of the following is a potential disadvantage associated with carbon farming?
Answer: Increased land clearing, promotion of monocultures, and loss of biodiversity.
Explanation: A potential disadvantage associated with carbon farming is the risk of increased land clearing, the promotion of monocultures, and a subsequent loss of biodiversity, which can negatively impact broader ecosystem services.
Which greenhouse gas, besides CO2, is highlighted as a more suitable subject for removal research due to its significantly longer atmospheric lifetime?
Answer: Nitrous oxide
Explanation: Beyond CO2, nitrous oxide is highlighted as a more suitable subject for greenhouse gas removal research due to its significantly longer atmospheric lifetime compared to other non-CO2 greenhouse gases like methane.
As of 2023, CDR methods are estimated to remove approximately 2 gigatons of CO2 annually, representing about 4% of human-caused greenhouse gas emissions.
Answer: True
Explanation: As of 2023, CDR methods are estimated to remove approximately 2 gigatons of CO2 per year, which accounts for about 4% of the total greenhouse gases emitted annually by human activities.
In 2023, almost all of the annual CO2 removed by CDR methods was achieved through high-tech approaches like Direct Air Capture.
Answer: False
Explanation: As of 2023, the vast majority of the 2 gigatons of CO2 removed annually by Carbon Dioxide Removal (CDR) methods is achieved through low-tech approaches such as reforestation and the creation of new forests, rather than high-tech solutions like Direct Air Capture.
What is the estimated annual amount of CO2 removed by CDR as of 2023?
Answer: Approximately 2 gigatons
Explanation: As of 2023, the estimated annual amount of CO2 removed by Carbon Dioxide Removal (CDR) methods is approximately 2 gigatons, representing about 4% of human-caused greenhouse gas emissions.
As of 2023, what type of CDR methods are primarily responsible for the majority of annual CO2 removal?
Answer: Low-tech approaches like reforestation and new forests
Explanation: As of 2023, the majority of annual CO2 removal by Carbon Dioxide Removal (CDR) methods is primarily achieved through low-tech approaches, such as reforestation and the establishment of new forests.
What is the estimated potential for Biochar Carbon Removal (BCR) in terms of annual carbon storage with increased effort?
Answer: 5–9 gigatons per year
Explanation: With increased effort in marketing and acceptance, the estimated potential for Biochar Carbon Removal (BCR) in soils could rise to 5–9 gigatons of carbon per year.
What is the estimated cost range per tonne for ocean alkalinity enhancement?
Answer: US$100 to $150
Explanation: The estimated cost range for ocean alkalinity enhancement as a Carbon Dioxide Removal (CDR) method is approximately US$100 to US$150 per tonne of CO2 removed.
Which CDR technology generally has the lowest cost per tonne?
Answer: Nature-based solutions (like reforestation)
Explanation: Among various Carbon Dioxide Removal (CDR) technologies, nature-based solutions such as reforestation and afforestation generally exhibit the lowest cost per tonne, typically less than $50.