CCS and climate change mitigation

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Carbon capture and storage (CCS) is a method used to reduce the amount of anthropogenic emissions of carbon dioxide (CO2) in the atmosphere in an attempt to limit the effects of global climate change. CCS can be employed to achieve a number of goals regarding climate change mitigation, such as preventing average global temperature from reaching certain levels above the pre-industrial average. In December 2015, the Paris Agreement articulated a census to not exceed pre-industrial global temperatures by more than 2 °C and recognized that different countries would have different contributions to help realize this goal. [1] Under the Paris Agreement, different scenarios and climate models were analyzed for different temperature goals considering a wide range of mitigation methods from a temperature goal of less than 2 °C to an upper limit of exactly 2 °C increase above the pre-industrial average.

Contents

The terms CCS and CCUS (Carbon Capture, Utilization, and Storage) are often used interchangeably. The difference between the two is the specified 'utilization' of the captured carbon and refers to its use for other applications, such as enhanced oil recovery (EOR), potentially making liquid fuel, or the manufacturing of useful consumer goods, such as plastics. Since both approaches capture emitted CO2 and effectively store it, whether that be under-ground in geological formations or long-term trapping in material products, the two terms are often treated the same.

CCS is considered as a basis of one climate stabilization wedge, which is a proposed climate mitigation action to reduce approximately 1 billion tonnes of carbon emissions over 50 years. [2]

CCS and different climate models

Carbon dioxide emissions and atmospheric concentrations over the 21st century Projected carbon dioxide emissions and atmospheric concentrations over the 21st century for reference and mitigation scenarios.png
Carbon dioxide emissions and atmospheric concentrations over the 21st century

Large scale CCS plays a crucial role in reaching climate change stabilization. According to the IPCC, the carbon emission patterns can greatly vary based on the uncertainty of human power consumption. A file regarding the fluctuations of greenhouse gas emissions is shown to the right. However, CCS' primarily role is to delay the shift from fossil fuels and thereby reducing transition costs. The implementation of default technology assumptions would cost 29-297% more over the century than efforts without CCS for a 430-480 ppm CO2/yr scenario. [3] [4] The Paris agreement upholds a goal to reach no more than a 2.0 °C increase above pre-industrial temperatures. If the 2.0 °C goal is to be reached in time, CCS must be utilized to achieve net zero emissions by 2060-2070. After 2060-2070, negative emissions will need to be achieved to remain below the 2.0 °C target. The variations in methods depend heavily on the climate change model being used and the anticipated energy consumption patterns. It is widely agreed upon, however, that CCS would need to be utilized if there is to be any negative climate change mitigation. [5]

CCS and 2.0°C target

The concept of a 2.0 °C came to light in the European Union of 1996 where the goal was to reduce the global temperature range relative pre-industrial levels. The decision of the 2 °C range was decided mostly on the evidence that many ecosystems are at risk if average global temperatures exceeded this limit. In order to limit the anthropogenic emissions such that there is no more than a 2 °C change relative to the periods between 1861 and 1880, carbon emissions would need to be limited to about 1000 GtC by 2100 since that period. However, by the end of 2011 about of half of the budget was already released (445 GtC) indicating that a lower budget is necessary. [6]

A distinctive path that aims for a 2.0 °C limit might have complications. The first complication involves the lack of positive feedback loops in IPCC climate models. These loops include reduction of ice sheet size, which would mean less sunlight is reflected and more is absorbed by the darker colored ground or water, and the potential release of greenhouse gases by thawing tundra. Since the lifetime of CO2 in the climate atmosphere is so long, these feedback loops have to be taken into consideration. Another important factor to consider is that a 2.0 °C scenario necessitates tapping into alternative fossil fuels sources that are harder to obtain. Some examples of these methods are the exploitation of tar sands, tar shales, hydrofracking for oil and gas, coal mining, drilling in the Arctic, Amazon, and deep ocean. Therefore, 2.0 °C scenarios result in more CO2 produced per unit of usable energy. Further, the danger of extra released CH4 via mining processes must be taken into account. [7]

Global greenhouse gas emissions by gas type Global emissions gas 2015.png
Global greenhouse gas emissions by gas type

Different models are based on when the peak of carbon emissions happen on a global scale. In one article regarding the 2.0 °C scenario with respect to pre-industrial levels, possible approaches are short term and long term emission resolutions as well as the considering the cost effectiveness of different solutions to reduce carbon emissions. Short term goals are set to quantify progress towards the temperature goal. In a short term goal, looking ahead to the year 2020, the allowable carbon emissions must be between 41 and 55 GtCO2 per year. The short term 2 °C scenario is not feasible without CCS. [8]

Currently, greenhouse gas emissions would need to be reduced by 7 Gt of carbon equivalent each year by 2050 to achieve 2 °C stabilization. This requires power generation with CCS at 800 coal-fired power plants of 1 GW energy generation capacity, 180 coal-synfuel plants, or natural gas plants worth 1,600 GW. [9] In this scenario, one of the wedges, or 1 Gt of carbon is accounted for by CCUS. [10] The cost of capturing CO2 is estimated to be $500/tC. If the goal with the 2.0 °C is to store a total of 7 Gt carbon per year, then the collective amount needed to achieve this is around 3.5 trillion U.S. dollars per year. The economic demand needed to achieve this goal is high. This amount of money is equivalent to gross national incomes for countries such as Russia or United Kingdom, and it represents 18% of United States' 2017 gross national income (19.61 trillion dollars). [3]

CCS and below 2.0°C target

Achieving below 2.0°C target

A change of temperature below 2 °C is, to certain extent, almost impossible to achieve due to the current carbon emission practices. The IPCC notes that it is difficult to assess a climate mitigation scenario that would limit average global temperature increase to only 1.5 °C above pre-industrial levels. This is mainly due to the fact that few reliable multi-model studies have been conducted to thoroughly explore this scenario. Nevertheless, what few studies that have been done agree that mitigation technologies must be implemented immediately and scaled up quickly and reflect energy demand decrease. [11] A change below 1 °C with respect to pre-industrial era is now inconceivable because by 2017 there was already an increase of 1 °C. [12]

Because of the immediate inability to control the temperature at the 1 °C target, the next realistic target is 1.5 °C. There is enough confidence that past emissions alone (pre-industrial time) will not be enough to go beyond the 1.5 °C target. In other words, if all anthropogenic emissions were stopped today (reduced to zero), any increase beyond the 1 °C change for more than half of a degree before 2100 is unlikely. If anthropogenic emission are considered, the probability for the planet increasing for more than 1.5 °C before 2100 are high. Then, scenarios where the degree change is maintain below 1.5 °C are very challenging to achieve but not impossible. [13]

For a below 2.0 °C target, Shared socioeconomic pathways (SSPs) had been developed adding a socio-economic dimension to the integrative work started by RCPs models. The advantage of using SSPs is that they incorporate social standards, fossil fuel use, geographical development, and high energy demand. SSPs also incorporate the use of six other models such as GCAM4, IMAGE, MESSAGE-GLOBIOM, and REMIND-MAgPIE. The combination of models and scenarios concluded that by 2050, annual CO2 emissions are in the range between 9 and 13 billion tons of CO2. All of the scenarios estimated that temperature will remain below 2.0 °C change with a 66% probability of success. To do so, a 1.9 W/m2 within the year 2100 is necessary. Net zero GHG emissions have to be achieved between 2055 and 2075, and CO2 emissions have to be in a range between 175 and 475 GtCO2 between the years 2016-2100. All SSPs scenarios show a shift away from unabated fossil fuels, that is process without CCS. [13]

Assumptions for below 2.0°C target

To achieve a 1.5 °C target before 2100, the following assumptions have to be considered; emissions have to peak by 2020 and decline after that, it will be necessary to reduce net CO2 emissions to zero and negative emissions have to be a reality by the second half of the 21st century. For this assumptions to take place, CCS has to be implemented in factories that accompany the use of fossil fuels. Because emissions reduction has to be implemented more rigorously for a 1.5 °C target, methods such as BEECS, and natural climate solutions such as afforestation can be used to aim in the reduction of global emissions. [14] BECCS is necessary to achieve a 1.5 °C. It is estimated by the models that with the help of BECCS, between 150 and 12000 GtCO2 still have to be removed from the atmosphere. [13]

Another negative emission strategy which includes CCS can also be approached through DACCS. Direct Air Carbon Capture and Sequestration (DACCS) is a carbon negative technology that utilizes solid amine based capture and it has proven to capture carbon dioxide from the air even though content of the air is much lower than of a flue gas from a coal plant. [15] However, it would require renewable energies to power since approximately 400kJ of work is needed per mole of CO2 capture. Furthermore, it is estimated that the total system cost is $1,000 per tonne of CO2, according to an economic and energetic analysis from 2011. [16]

Going forward in the utilization of models such as SSPss and RCP, feasibility of the model has to be to take into consideration. Feasibility includes concerns in various fields, such as geophysics, technology, economics, social acceptance, and politics, all of which can serve to facilitate or obstruct the carbon capture and sequestration of emissions needed in order to achieve the global temperature targets. Uncertainty in feasibility is especially a problem with more strict temperatures limits such as 1.5 °C. Real world feasibility of SSPs models, or any other models, in general are coarse approximations of reality. [13]

Related Research Articles

The United Nations Framework Convention on Climate Change (UNFCCC) established an international environmental treaty to combat "dangerous human interference with the climate system", in part by stabilizing greenhouse gas concentrations in the atmosphere. It was signed by 154 states at the United Nations Conference on Environment and Development (UNCED), informally known as the Earth Summit, held in Rio de Janeiro from 3 to 14 June 1992. It established a Secretariat headquartered in Bonn and entered into force on 21 March 1994. The treaty called for ongoing scientific research and regular meetings, negotiations, and future policy agreements designed to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner.

The Special Report on Emissions Scenarios (SRES) is a report by the Intergovernmental Panel on Climate Change (IPCC) that was published in 2000. The greenhouse gas emissions scenarios described in the Report have been used to make projections of possible future climate change. The SRES scenarios, as they are often called, were used in the IPCC Third Assessment Report (TAR), published in 2001, and in the IPCC Fourth Assessment Report (AR4), published in 2007.

Climate change mitigation Actions to limit global warming and its related effects on humanity and the Earth

Climate change mitigation consists of actions to limit global warming and its related effects. This is mainly reductions in human emissions of greenhouse gases (GHGs) as well as activities that reduce their concentration in the atmosphere. It is one of the ways to respond to climate change, along with adaptation. Fossil fuels emit most carbon dioxide(CO2) and greenhouse gas as a whole. The most important challenge is to stop burning coal, oil, and gas and use only clean energy. Due to massive price drops, wind power and solar photovoltaics (PV) are increasingly out-competing oil, gas and coal though these require energy storage and improved electrical grids. As low-emission energy is deployed at large scale, transport and heating can shift to these mostly electric sources. Mitigation of climate change may also be achieved by changes in agriculture, transport, forest-management, waste management, buildings, and industrial systems. Methane emissions, which have a high short-term impact, can be targeted by reductions in dairy products and meat consumption.

Economics of climate change

The economics of climate change concerns the economic aspects of climate change; this can inform policies that governments might consider in response. A number of factors make this and the politics of climate change a difficult problem: it is a long-term, intergenerational problem; benefits and costs are distributed unequally both within and across countries; and both the scientific consensus and public opinion on climate change need to be taken into account.

Carbon capture and storage Process of capturing and storing waste carbon dioxide from point sources

Carbon capture and storage (CCS) or carbon capture and sequestration is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting it, and storing it (carbon sequestration) for centuries or millennia. Usually the CO2 is captured from large point sources, such as coal-fired power plant, a chemical plant or biomass power plant, and then stored in an underground geological formation. The aim is to prevent the release of CO2 from heavy industry with the intent of mitigating the effects of climate change. Although CO2 has been injected into geological formations for several decades for various purposes, including enhanced oil recovery, the long-term storage of CO2 is a relatively new concept. Carbon capture and utilization (CCU) and CCS are sometimes discussed collectively as carbon capture, utilization, and sequestration (CCUS). This is because CCS is a relatively expensive process yielding a product with an intrinsic low value (i.e. CO2). Hence, carbon capture makes economically more sense when being combined with a utilization process where the cheap CO2 can be used to produce high-value chemicals to offset the high costs of capture operations.

Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC) was published in 2007 and is the fourth in a series of reports intended to assess scientific, technical and socio-economic information concerning climate change, its potential effects, and options for adaptation and mitigation. The report is the largest and most detailed summary of the climate change situation ever undertaken, produced by thousands of authors, editors, and reviewers from dozens of countries, citing over 6,000 peer-reviewed scientific studies. People from over 130 countries contributed to the IPCC Fourth Assessment Report, which took 6 years to produce. Contributors to AR4 included more than 2500 scientific expert reviewers, more than 800 contributing authors, and more than 450 lead authors.

Climate change Current rise in Earths average temperature and its effects

Contemporary climate change includes both global warming and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current changes are distinctly more rapid and not due to natural causes. Instead, they are caused by the emission of greenhouse gases, mostly carbon dioxide and methane. Burning fossil fuels for energy use creates most of these emissions. Certain agricultural practices, industrial processes, and forest loss are additional sources. Greenhouse gases are transparent to sunlight, allowing it through to heat the Earth's surface. When the Earth emits that heat as infrared radiation the gases absorb it, trapping the heat near the Earth's surface. As the planet heats up it causes changes like the loss of sunlight-reflecting snow cover, amplifying global warming.

Virgin Earth Challenge

The Virgin Earth Challenge was a competition offering a $25 million prize for whoever could demonstrate a commercially viable design which results in the permanent removal of greenhouse gases out of the Earth's atmosphere to contribute materially in global warming avoidance. The prize was conceived by Richard Branson, and was announced in London on 9 February 2007 by Branson and former US Vice President Al Gore. However, the prize was never awarded. In 2019, Virgin quietly took the prize website offline, after keeping 11 finalists suspended in expectation for eight years. Al Gore had withdrawn from the jury earlier and commented that "He was not part of the decision to discontinue the contest.".

Greenhouse gas emissions Sources and amounts of greenhouse gases emitted to the atmosphere from human activities

Greenhouse gas emissions from human activities strengthen the greenhouse effect, causing climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and large oil and gas companies, many state-owned by OPEC and Russia. Human-caused emissions have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but it was consistent among all greenhouse gases. Emissions in the 2010s averaged 56 billion tons a year, higher than ever before.

IPCC Fifth Assessment Report Intergovernmental report on climate change

The Fifth Assessment Report (AR5) of the United Nations Intergovernmental Panel on Climate Change (IPCC) is the fifth in a series of such reports and was completed in 2014. As had been the case in the past, the outline of the AR5 was developed through a scoping process which involved climate change experts from all relevant disciplines and users of IPCC reports, in particular representatives from governments. Governments and organizations involved in the Fourth Report were asked to submit comments and observations in writing with the submissions analysed by the panel. AR5 followed the same general format as of AR4, with three Working Group reports and a Synthesis report. The report was delivered in stages, starting with the report from Working Group I in September 2013 which reported on the physical science basis, based on 9,200 peer-reviewed studies. Projections in AR5 are based on "Representative Concentration Pathways" (RCPs). The RCPs are consistent with a wide range of possible changes in future anthropogenic greenhouse gas emissions. Projected changes in global mean surface temperature and sea level are given in the main RCP article. The Synthesis Report was released on 2 November 2014, in time to pave the way for negotiations on reducing carbon emissions at the UN Climate Change Conference in Paris during late 2015.

Carbon dioxide removal Removal of carbon dioxide in the atmosphere

Carbon dioxide removal (CDR), also known as negative CO2 emissions, is a process in which carbon dioxide gas is removed from the atmosphere and sequestered for long periods of time. Similarly, greenhouse gas removal (GGR) or negative greenhouse gas emissions is the removal of greenhouse gases (GHGs) from the atmosphere by deliberate human activities, i.e., in addition to the removal that would occur via natural carbon cycle or atmospheric chemistry processes. In the context of net zero greenhouse gas emissions targets, CDR is increasingly integrated into climate policy, as a new element of mitigation strategies. CDR and GGR methods are also known as negative emissions technologies (NET), and may be cheaper than preventing some agricultural greenhouse gas emissions.

Bioenergy with carbon capture and storage (BECCS) is the process of extracting bioenergy from biomass and capturing and storing the carbon, thereby removing it from the atmosphere. The carbon in the biomass comes from the greenhouse gas carbon dioxide (CO2) which is extracted from the atmosphere by the biomass when it grows. Energy is extracted in useful forms (electricity, heat, biofuels, etc.) as the biomass is utilized through combustion, fermentation, pyrolysis or other conversion methods. Some of the carbon in the biomass is converted to CO2 or biochar which can then be stored by geologic sequestration or land application, respectively, enabling carbon dioxide removal (CDR) and making BECCS a negative emissions technology (NET).

The Copenhagen Accord is a document which delegates at the 15th session of the Conference of Parties to the United Nations Framework Convention on Climate Change agreed to "take note of" at the final plenary on 18 December 2009.

Climate change scenario Projections of future greenhouse gas emissions

Climate change scenarios or socioeconomic scenarios are projections of future greenhouse gas (GHG) emissions used by analysts to assess future vulnerability to climate change. Scenarios and pathways are created by scientists to survey any long term routes and explore the effectiveness of mitigation and helps us understand what the future may hold this will allow us to envision the future of human environment system. Producing scenarios requires estimates of future population levels, economic activity, the structure of governance, social values, and patterns of technological change. Economic and energy modelling can be used to analyze and quantify the effects of such drivers.

Representative Concentration Pathway Projections used in climate change modeling

A Representative Concentration Pathway (RCP) is a greenhouse gas concentration trajectory adopted by the IPCC. Four pathways were used for climate modeling and research for the IPCC fifth Assessment Report (AR5) in 2014. The pathways describe different climate futures, all of which are considered possible depending on the volume of greenhouse gases (GHG) emitted in the years to come. The RCPs – originally RCP2.6, RCP4.5, RCP6, and RCP8.5 – are labelled after a possible range of radiative forcing values in the year 2100. Since AR5 the original pathways are being considered together with Shared Socioeconomic Pathways: as are new RCPs such as RCP1.9, RCP3.4 and RCP7.

Climate restoration

Climate restoration is the climate change goal and associated actions to restore CO2 to levels humans have survived long-term, below 300 ppm. This would restore the Earth system generally to a safe state, for the well-being of future generations of humanity and nature. Actions include carbon dioxide removal from the Carbon dioxide in Earth's atmosphere, which, in combination with emissions reductions, would reduce the level of CO2 in the atmosphere and thereby reduce the global warming produced by the greenhouse effect of an excess of CO2 over its pre-industrial level. Actions also include restoring pre-industrial atmospheric methane levels by accelerating natural methane oxidation.

Carbon budget Limit on carbon dioxide emission for a given climate impact

A carbon budget is “the maximum amount of cumulative net global anthropogenic carbon dioxide emissions that would result in limiting global warming to a given level with a given probability, taking into account the effect of other anthropogenic climate forcers”. When expressed relative to the pre-industrial period it is referred to as the Total Carbon Budget, and when expressed from a recent specified date it is referred to as the Remaining Carbon Budget.

The Special Report on Global Warming of 1.5 °C (SR15) was published by the Intergovernmental Panel on Climate Change (IPCC) on 8 October 2018. The report, approved in Incheon, South Korea, includes over 6,000 scientific references, and was prepared by 91 authors from 40 countries. In December 2015, the 2015 United Nations Climate Change Conference called for the report. The report was delivered at the United Nations' 48th session of the IPCC to "deliver the authoritative, scientific guide for governments" to deal with climate change.

Shared Socioeconomic Pathways How the world might change up to the end of the 21st century

Shared Socioeconomic Pathways (SSPs) are scenarios of projected socioeconomic global changes up to 2100. They are used to derive greenhouse gas emissions scenarios with different climate policies.

The Sixth Assessment Report (AR6) of the United Nations (UN) Intergovernmental Panel on Climate Change (IPCC) is the sixth in a series of reports which assess scientific, technical, and socio-economic information concerning climate change. Three Working Groups have been working on the following topics:

  1. The Physical Science Basis (WGI)
  2. Impacts, Adaptation and Vulnerability (WGII)
  3. Mitigation of Climate Change (WGIII).

References

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  2. ↑ "Stabilization Wedges Introduction | Carbon Mitigation Initiative". cmi.princeton.edu. Retrieved 2018-12-02.
  3. 1 2 "DOE - Carbon Capture Utilization and Storage_2016!09!07 | Carbon Capture And Storage | Climate Change Mitigation". Scribd. Retrieved 2018-12-03.
  4. ↑ Pye, Steve; Li, Francis G. N.; Price, James; Fais, Birgit (March 2017). "Achieving net-zero emissions through the reframing of UK national targets in the post-Paris Agreement era" (PDF). Nature Energy. 2 (3). doi:10.1038/nenergy.2017.24. ISSN   2058-7546.
  5. ↑ Rogelj, Joeri; Schaeffer, Michiel; Meinshausen, Malte; Knutti, Reto; Alcamo, Joseph; Riahi, Keywan; Hare, William (2015). "Zero emission targets as long-term global goals for climate protection". Environmental Research Letters. 10 (10): 105007. doi: 10.1088/1748-9326/10/10/105007 . ISSN   1748-9326.
  6. ↑ Intergovernmental Panel on Climate Change, ed. (2014), "Near-term Climate Change: Projections and Predictability", Climate Change 2013 - the Physical Science Basis, Cambridge University Press, pp. 953–1028, doi:10.1017/cbo9781107415324.023, ISBN   9781107415324
  7. ↑ Hansen, James; Kharecha, Pushker; Sato, Makiko; Masson-Delmotte, Valerie; Ackerman, Frank; Beerling, David J.; Hearty, Paul J.; Hoegh-Guldberg, Ove; Hsu, Shi-Ling (2013-12-03). "Assessing "Dangerous Climate Change": Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature". PLOS ONE. 8 (12): e81648. doi: 10.1371/journal.pone.0081648 . ISSN   1932-6203. PMC   3849278 . PMID   24312568.
  8. ↑ Rogelj, Joeri; McCollum, David L.; O'Neill, Brian C.; Riahi, Keywan (2012-12-16). "2020 emissions levels required to limit warming to below 2 °C". Nature Climate Change. 3 (4): 405–412. doi:10.1038/nclimate1758. ISSN   1758-678X.
  9. ↑ "The Wedge Approach to Climate Change | World Resources Institute". www.wri.org. Retrieved 2018-12-04.
  10. ↑ "Carbon Capture, Utilization, and Storage: Climate Change, Economic Competitiveness, and Energy Security" (PDF). www.energy.gov. U.S. Department of Energy. August 2016. Retrieved 2018-12-04.
  11. ↑ "Intergovernmental Panel on Climate Change (IPCC) Global Surface Warming Scenarios", Multimedia Atlas of Global Warming and Climatology, SAGE Publications Ltd, 2014, doi:10.4135/9781483351384.n48, ISBN   9781483351384
  12. ↑ M. R. Allen, O. P. Dube, W. Solecki, F. Aragón–Durand, W. Cramer, S. Humphreys, M. Kainuma, J. Kala, N. Mahowald, Y. Mulugetta, R. Perez, M. Wairiu, K. Zickfeld, 2018, Framing and Context. In: Global warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [V. Masson-Delmotte, P. Zhai, H. O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J. B. R. Matthews, Y. Chen, X. Zhou, M. I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, T. Waterfield (eds.)]. In Press.
  13. 1 2 3 4 Tavoni, Massimo; Stehfest, Elke; Humpenöder, Florian; Havlík, Petr; Harmsen, Mathijs; Fricko, Oliver; Edmonds, Jae; Drouet, Laurent; Doelman, Jonathan (April 2018). "Scenarios towards limiting global mean temperature increase below 1.5 °C" (PDF). Nature Climate Change. 8 (4): 325–332. doi:10.1038/s41558-018-0091-3. hdl:1874/372779. ISSN   1758-6798. S2CID   56238230.
  14. ↑ "New scenarios show how the world could limit warming to 1.5C in 2100". Carbon Brief. 2018-03-05. Retrieved 2018-12-06.
  15. ↑ Choi, Sunho; Drese, Jeffrey H.; Eisenberger, Peter M.; Jones, Christopher W. (2011-03-15). "Application of Amine-Tethered Solid Sorbents for Direct CO2Capture from the Ambient Air". Environmental Science & Technology. 45 (6): 2420–2427. doi:10.1021/es102797w. ISSN   0013-936X. PMID   21323309.
  16. ↑ House, Kurt Zenz; Baclig, Antonio C.; Ranjan, Manya; Nierop, Ernst A. van; Wilcox, Jennifer; Herzog, Howard J. (2011-12-20). "Economic and energetic analysis of capturing CO2 from ambient air". Proceedings of the National Academy of Sciences. 108 (51): 20428–20433. doi: 10.1073/pnas.1012253108 . ISSN   0027-8424. PMC   3251141 . PMID   22143760.
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