Reasons, requirements, and realities

A look at the challenges in limiting global warming, progress made at 26^th UN Climate Change Conference of the Parties (COP26) in Glasgow, and what more chemistry can contribute.

Global warming is being driven by human activities generating atmospheric greenhouse gases (GHGs). As the resulting climate effects intensify, there will be long-term consequences for the habitability of large regions of the planet’s surface. Achieving stability and sustaining the present type of climate requires limiting the temperature increase to not more than 1.5°C above pre-industrial levels.¹⁾ The 2015 Paris Agreement on climate change committed governments to limiting warming to well below 2°C above pre-industrial levels and to “pursuing efforts” to prevent more than 1.5°C of warming. However, human-induced warming has already reached about 1.1°C above pre-industrial levels and, at the present rate, global temperatures would reach 1.5°C around 2040 and 2.7°C by the end of the century.²⁾ The COP26 conference³⁾ in Glasgow in November 2021 was framed as the last opportunity for the world to correct its course and credibly retain the 1.5–2.0^oC goal.⁴⁾

Greenhouse gases

Unlike the main constituents of air, CO₂ absorbs the infrared energy produced by sunlight reflecting off the Earth’s surface, which would otherwise escape back into space. The CO₂ then re-radiates the infrared energy in all directions, and much of the energy remains on Earth, leading to warming. For at least the last 800,000 years, the level of CO₂ in the atmosphere oscillated in a range from about 180 ppm up to 300 ppm.⁵⁾ However, since the mid-20^th century, the level has been increasing rapidly, surpassing 400 ppm in 2013 and reaching 412.4 ppm in 2020. This atmospheric CO₂ level was last seen more than three million years ago,⁶⁾ when the temperature was 2°–3°C higher than during our pre-industrial era and the sea level was 15–25 metres higher than today.

Three gases make up most of the GHG emissions:⁷⁾

CO₂ generated by burning carbon-containing materials causes three-quarters of the total man-made GHG effect. Furthermore, the manufacture of cement powder from mixtures containing CaCO₃ liberates CO₂ both from the generation of heat from combustion of fossil fuels and from the high-temperature decomposition of the CaCO₃. Cement production accounts for 8% of the world’s total annual emissions of CO₂.⁸⁾ Together, burning fossil fuels for energy and producing cement emit over 36 Bn tonnes/year of CO₂ globally, out of the annual total of around 43 Bn tonnes.

CH₄ accounts for 17% of the total GHG effect. It arises from three main sources: about 20% from the bacterial decomposition of organic waste, 36% from leakages from the production and use of fossil fuels, and 44% from agriculture.⁹⁾ Nearly three-quarters of the agriculture-derived CH₄ is produced by fermentation of food being digested by animals, and nearly one-quarter through the action of microbes in fields – about half of this in flooded rice paddies.¹⁰⁾ Methane’s role in global warming is especially important because it is about 80 times more powerful than CO₂ as a GHG, but it is a relatively short-lived, breaking down after an average of around 12 years in the atmosphere while CO₂ may persist for thousands of years.¹¹⁾ Thus, immediate major reductions in the amount of CH₄ being emitted can yield significant near-term reductions in the global warming potential of the atmosphere.

N₂O sources in the atmosphere include some industrial emission, but mostly agriculture, where it is formed by the action of microbes on nitrogen compounds in fertilised soils and animal manure. Weight-for-weight, N₂O warms the atmosphere about 265 times as much as CO₂ and it has an average atmospheric lifetime of 121 years. Overall, it represents about 6% of the greenhouse warming capacity of the atmosphere.¹¹⁾

Science solutions are available, but COP26 made limited progress

To limit climate change, effort is necessary in two major areas. One is to end the destruction of forests that help retain already locked-in carbon and remove carbon dioxide present in the atmosphere. In the Glasgow Leaders’ Declaration on Forests and Land Use,¹²⁾ 91% of the world’s forests were covered by a pledge from 137 countries to halt and reverse forest loss and land degradation by 2030. However, there are fears that implementation of this Declaration may be weak: Its forerunner, the 2014 New York Declaration, had failed to slow deforestation.¹³⁾

The complementary critical step is to cease emitting GHGs into the atmosphere. This requires a range of interventions across all the major sectors and activities that presently generate GHG emissions and, in each area, using different, overlapping approaches that will have short-, medium- and long-term effects. The final outcome document from COP26, the Glasgow Climate Pact,¹⁴⁾ made some progress, but while it reaffirms the 2015 Paris Agreement goal to pursue efforts to achieve the 1.5^oC global warming limit, the urging¹⁵⁾ to “keep 1.5 alive” did not result in commitments that would deliver this result.¹⁶⁾ Many of the largest economies, including China, the European Union (EU), and the USA, announced targets of net zero emissions by 2050, while India unveiled plans for the first time for achieving net zero emissions – but 20 years later, by 2070. Estimates suggest that, if all the pledges made in Glasgow were fully met, a temperature rise limited to 1.8–1.9^oC is feasible,^15a) but it is widely expected that implementation will fall significantly short of this.

Energy

Eliminating CO₂ emissions will require largely, if not completely, ceasing to burn fossil fuels, only continuing their consumption when the CO₂ produced is captured and locked into long-term storage forms or other uses where it is not released into the atmosphere. In 2019, oil provided about 39% of the energy from fossil fuels, coal 32%, and gas 29%.¹⁷⁾ Coal is currently the most heavily polluting of the major fossil fuels since, in addition to CO₂, combustion emits sulphur oxides from sulphur impurities it contains as well fine particulate matter that adds to local environmental contamination and health hazards, and it leaves ash to be disposed of. Reducing coal consumption in favour of natural gas (mainly CH₄) provides immediate benefits in terms of reducing emissions of coal-derived pollutants and GHGs (as seen, e.g., in Germany, the UK and the USA). However, natural gas, even when completely combusted, still releases about 50–60% of CO₂ emissions compared to coal. Moreover, leakages of CH₄ always occur during extraction, transport, and combustion. Methane’s much higher global warming potential means that the leakage rate must be kept below 3–5% (the exact break-even point depends¹⁸⁾ on what type of coal is being substituted); otherwise there is still a net increase in the greenhouse effect.

Over 100 countries attending COP26 agreed to reduce CH₄ emissions by 30% by 2030. The USA’s own blueprint¹⁹⁾ for achieving this emphasised action on several fronts, including: cutting leakages and emissions from the oil and gas sector (the largest source), reducing CH₄ emissions by remediating abandoned coal mines, reducing food loss and waste that serves as a major contributor to landfill CH₄ emissions, and initiating an incentive-based “climate-smart” agriculture programme, in particular with attention to alternative manure management systems. Canada announced that it would cut CH₄ emissions from its large oil and gas industry by 75% by 2030. According to the International Energy Agency’s Net Zero by 2050 Roadmap,²⁰⁾ that is how fast overall global CH₄ emissions will need to be cut if the world is to reach net zero by mid-century.

Alternatives to fossil fuel combustion for the long term include geothermal, hydroelectric, nuclear, solar, wind, and wave sources of energy. All these options avoid CO₂ emissions at the point of energy generation, but each presents a range of other challenges – including technical, economic, environmental, social, and political – that need to be worked through. Moreover, each method requires specific hardware. This may range from large constructions (e.g., dams, turbines) to sophisticated devices (e.g., solar cells and panels) – all of which, on a scale that would be needed for global effect, would require massively increased operations for mining, refining, transport, material transformations, assembly and installation, maintenance, and renewal.²¹⁾

The Glasgow Climate Pact final text calls for rapid scale-up of the deployment of clean power generation and energy efficiency measures, including “accelerating efforts towards the phase-down of unabated coal power and inefficient fossil fuel subsidies”. While including a reference to coal for the first time, a late intervention led by India and China watered down an earlier draft text that had called for the phase-out of coal.²²⁾

Transport

Developing alternative mobile forms of energy is the core challenge in eliminating GHG emissions in the transport sector. Transport presently accounts for around one-fifth of global CO₂ emissions, with the largest three contributors being passenger cars, trucks, and aviation.²³⁾ One approach to the replacement of oil products for the internal combustion engine involves the storage of energy in batteries for electric vehicles. The technical challenges of increasing the power of batteries (currently based on Li) and reducing charging time are gradually being overcome, and a number of countries are setting target dates within the next one to two decades for phasing out oil-based in favour of electric vehicles. As with energy production at fixed locations, the question of the sourcing and turnover of the necessary materials on a global scale needs to be carefully considered. For example, the restricted geographical locations of known, accessible supplies of Li have led to concerns about the potential to satisfy projected world demands.²¹⁾ Efforts to meet the challenge include developing the recycling²⁴⁾ of Li batteries, while alternative Li sources (e.g., seawater extraction²⁵⁾) and replacement materials (e.g., Al, Mg, Na, Zn) are being explored.

An alternative is the replacement of oil-based fuels with substances that can be carried in the vehicle and used to create the motive force required. Options include the use of H₂ fuel cells, or combusting materials such as H₂ without liberating pollutants. However, H₂ is currently derived from CH₄, with co-generation of CO₂, and it would need to be made instead by splitting water using energy from solar or other non-carbon-based sources. Also, transport of H₂ presents dangers of leakages, fires, and explosions. Recently, there has been rising interest in the possible use of NH₃ as a fuel.²⁶⁾ It can also be burned in a combustion engine, producing N₂ and H₂O, and has a higher energy content than H₂. Ammonia is liquified at a much higher temperature (–33^oC) than H₂ (–253^oC) but is not as highly flammable. However, NH₃ is toxic by inhalation and acts as a severe respiratory tract irritant. Furthermore, the Haber-Bosch industrial process used for the last 100 years to manufacture NH₃ itself emits very large amounts of CO₂, and new “green NH₃” technologies²⁷⁾ are needed to make this a carbon-free energy alternative.

Clean technologies

Across the political negotiations and agreements on individual targets for reducing GHG emissions and preserving and restoring forests and soils, there was recognition that technology would play a crucial role. More than 40 countries attending COP26, including Australia, China, the EU, India, Turkey, and the USA, agreed on a UK-led plan, the “Breakthrough Agenda”,²⁸⁾ to speed up affordable and clean technology worldwide by 2030. Five initial goals set out were:

Power: Clean power becomes the most affordable and reliable option worldwide.

Road transport: Zero-emission vehicles become the new normal and are accessible, affordable, and sustainable in all regions.

Steel: Near-zero emission steel is the preferred choice in global markets, with efficient use and near-zero emission steel production established and growing in all regions.

Hydrogen: The aim is for affordable renewable and low-carbon hydrogen to be globally available.

Agriculture: Climate-resilient, sustainable agriculture becomes the most attractive and widely adopted option for farmers everywhere.

While investments would be needed to make these breakthroughs, it was projected that they could create 20 million new jobs globally and add over 16 trillion U. S. Dollar across both emerging and advanced economies.

Outlook

Ending GHG emissions will require massive efforts by all countries and carries implications for many aspects of economies, transport, food production, and much else. Consequently, the decisions taken in COP26 and to be taken in future climate negotiations, while needing to be rooted in sound science and technology, are all ultimately political. For greatest impact, chemistry must therefore be active in both science and policy-shaping.

In a nutshell

Chemical processes are at the core of the anthropogenic production of atmospheric greenhouse gases (GHGs) in industry, agriculture and the environment.

Chemistry must therefore be central to reaching the objective of limiting global warming, through helping clean up the atmosphere and develop smarter materials, technologies and processes that prevent GHG release.

Efforts in these areas are under way, but urgently need to be intensified.

The authors

The article was written by members of Chemists for Sustainability (C4S), an action group of the International Organization for Chemical Sciences in Development (IOCD). C4S has received support from GDCh and Royal Society of Chemistry. Authors are: Henning Hopf (right), former President of the German Chemical Society, Alain Krief (second from left), former Executive Director of the IOCD, Goverdhan Mehta (left), University of Hyderabad, India; Stephen A. Matlin, Visiting Professor, Imperial College London, UK and Senior Fellow in the Global Health Centre, Geneva, Switzerland.

• ¹ A. Myles et al. Special Report: Global Warming of 1.5 ºC. Summary for Policymakers. In: Global Warming of 1.5°C. An IPCC Special Report. Geneva, Intergovernmental Panel on Climate Change, 2018
• ² Climate change widespread, rapid, and intensifying – IPCC. Geneva, Intergovernmental Panel on Climate Change, 9 August 2021
• ³ COP26: 26th Meeting of the Conference of the Parties of the UN Climate Change Conference, held in Glasgow, UK, 31 October – 12 November 2021
• ⁴ A. Guterres. Secretary-General‘s remarks to the High-Level Meeting on Delivering Climate Action – for People, Planet & Prosperity. New York, United Nations 26 October 2021
• ⁵ The relentless rise of carbon dioxide. NASA Jet Propulsion Laboratory, California Institute of Technology 8 December 2021. https://climate.nasa.gov/climate_resources/24/graphic-the-relentless-rise-of-carbon-dioxide/
• ⁶ R. Lindsey. Climate change: Atmospheric carbon dioxide. Climate.gov 7 October 2021. https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide
• ⁷ H. Ritchie, M. Roser. Greenhouse Gas Emissions. OurWorldInData.org, 2020. https://ourworldindata.org/greenhouse-gas-emissions
• ⁸ J. Lehne, F. Preston. Making concrete change: Innovation in low-carbon cement and concrete. London, Chatham House, https://www.chathamhouse.org/2018/06/making-concrete-change-innovation-low-carbon-cement-and-concrete
• ⁹ J. Lynch. Agricultural methane and its role as a greenhouse gas. Table 11 June 2019. https://www.tabledebates.org/building-blocks/agricultural-methane-and-its-role-greenhouse-gas
• ¹⁰ S. Fleming. This is how rice is hurting the planet. Geneva: World Economic Forum 18 June 2019. https://www.weforum.org/agenda/2019/06/how-rice-is-hurting-the-planet/
• ¹¹ G. Myhre et al. Anthropogenic and natural radiative forcing. In: Climate change 2013: The physical science basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge UK, Cambridge University Press, 2013
• ¹² The Glasgow Leaders’ Declaration on Forests and Land Use. UN Climate Change Conference, Glasgow 2 November 2021
• ¹³ a) J.P Moreiras. FFI’s response to the Glasgow Leaders’ Declaration on Forest and Land Use. Cambridge UK: Fauna & Flora International, 2 November 2021; b) R.A. Butler. Do forest declarations work? How do the Glasgow and New York declarations compare? Menlo Park, CA, Mongabay, 4 November 2021. https://news.mongabay.com/2021/11/how-do-the-u-n-forest-declarations-compare/
• ¹⁴ The Glasgow Climate Pact, annotated. Washington Post, 13 November 2021. https://www.washingtonpost.com/climate-environment/interactive/2021/glasgow-climate-pact-full-text-cop26/
• ¹⁵ a) A. Guterres. Statement by UN Secretary-General: COP26 must keep 1.5 degrees Celsius goal alive. New York: United Nations 1 November 2021; b) At UN climate change conference, trying to “keep 1.5 alive”. MIT News 17 November 2021. https://news.mit.edu/2021/un-climate-change-conference-cop26–1117
• ¹⁶ COP26: The Glasgow Climate Pact. UK Government 2021. https://ukcop26.org/wp-content/uploads/2021/11/COP26-Presidency-Outcomes-The-Climate-Pact.pdf
• ¹⁷ H. Ritchie, M. Roser. Energy: Global fossil fuel consumption. OurWorldInData.org, 2020. https://ourworldindata.org/fossil-fuels#global-fossil-fuel-consumption
• ¹⁸ S. Ladage et al., Sci. Rep. 2021, 11, 11453.
• ¹⁹ US methane emissions reduction action plan. Washington DC: The White House, November 2021. https://www.whitehouse.gov/wp-content/uploads/2021/11/US-Methane-Emissions-Reduction-Action-Plan-1.pdf
• ²⁰ Curtailing methane emissions from fossil fuel operations. Paris: International Energy Agency 2021
• ²¹ K. Hund, D. La Porta, T.P. Fabregas, T. Laing, J. Drexhage. Minerals for climate action: The mineral intensity of the clean energy transition. Washington DC, The World Bank, 2020
• ²² India proposes new wording on phasing coal „down“ not „out“. Reuters 13 November 2021. https://www.reuters.com/business/cop/india-proposes-new-wording-phasing-coal-down-not-out-2021–11–13/
• ²³ H. Ritchie. Cars, planes, trains: where do CO2 emissions from transport come from? OurWorldInData.org, 24 September 2021. https://ourworldindata.org/co2-emissions-from-transport
• ²⁴ P. Patel. Study: Recycled lithium batteries as good as newly mined. IEEE Spectrum, 15 Oct 2021
• ²⁵ M. Jacoby, Chem. Eng. News 2021, 99(36), 28 September
• ²⁶ A. Valera-Medina et al., Energy Fuels 2021, 35(9), 6964
• ²⁷ C. Smith, A.K. Hill, L. Torrente-Murciano, Energy Environ. Sci. 2020, 13, 331
• ²⁸ Breakthrough Agenda – Launching an annual Global Checkpoint Process in 2022. Glasgow, COP26, 9 November 2021. https://ukcop26.org/breakthrough-agenda-launching-an-annual-global-checkpoint-process-in-2022/

Bildung + Gesellschaft