Co-Benefits of Cutting Black Carbon and Ground-level Ozone

A new UN study highlights the potential benefits of reducing specific air pollutants which not only help to prevent climate change but have a number of positive benefits for human health and agriculture.

If the world is to avoid dangerous climate change and keep a twenty-first century temperature rise below two degrees Celsius or less, it will be necessary to achieve a significant reduction in emissions of carbon dioxide – a key greenhouse gas.

However, the United Nations Environment Programme (UNEP) and the World Meterological Organisation (WMO) report coordinated by the Stockholm Environment Institute on Integrated Assessment of Black Carbon and Tropospheric Ozone shows that the measures can reduce near-term climate change and premature deaths and crop loss by taking action to reduce these two pollutants.

Black carbon exists as particles in the atmosphere and is a major component of soot. At ground level ozone is an air pollutant harmful to human health and ecosystems and, throughout the lower atmosphere, is also a significant greenhouse gas. Ozone is not directly emitted, but is produced from emissions of precursors of which methane and carbon monoxide are of particular interest.

Black carbon and ozone in the lower atmosphere are harmful air pollutants that have substantial regional and global climate impacts. They disturb tropical rainfall and regional circulation patterns (e.g. the Asian monsoon) affecting the livelihoods of millions of people.

Black carbon’s darkening of snow and ice surfaces increases their absorption of sunlight which, along with global warming, exacerbates melting of snow and ice around the world. This affects the water cycle and increases the risk of flooding.

Black carbon, a component of particulate matter, and ozone both lead to premature deaths worldwide. Ozone is also the most important air pollutant responsible for reducing crop yields and affects food security.

The UNEP/WMO study calls for immediate action to reduce emissions of black carbon and tropospheric ozone, which have the potential to slow the rate of climate change within the first half of this century.

Climate benefits from cutting ozone are achieved by reducing emissions of some of its precursors, especially methane which is also a powerful greenhouse gas. These short-lived climate gases (e.g. black carbon and methane) only remain in the atmosphere for a short time compared to longer-lived greenhouse gases (e.g. carbon dioxide).

The study also highlights how a small number of emission reduction measures targeting black carbon and ozone precursors could immediately begin to protect climate, public health, water and food security, and ecosystems.

The measures include the recovery of methane from coal, oil and gas extraction and transport, methane capture in waste management, use of clean-burning stoves for residential cooking, diesel particulate filters for vehicles and the banning of open burning of agricultural waste.

Full implementation is achievable with existing technology but would require significant and strategic investment and institutional arrangements.

The study claims that the full implementation of the identified measures would reduce future global warming by 0.5 degrees Celsius (within a range of 0.2 – 0.7 Celsius). If the measures were to be implemented by 2030, this could halve the potential increase in global temperature projected for 2050 compared to a reference scenario based on current policies and energy and fuel projections. The rate of regional temperature increase would also be reduced.

In addition, implementation of all the measures could avoid 2.4 million premature deaths (within a range of 0.7- 4.6 million) and the loss of 52 million tonnes (within a range of 30.140 million tonnes), 1.4 per cent, of global production of maize, rice, soybean and wheat each year. The most substantial benefits will be felt immediately in or close to the regions where action is taken to reduce emissions, with the greatest health and crop benefits expected.

The study concludes that there is confidence that immediate and multiple benefits will be achieved upon implementation of the identified measures. The degree of confidence varies according to pollutant, impact and region.

For example, there is higher confidence in the effect of methane measures on global temperatures than in the effect of black carbon measures, especially where these relate to the burning of biomass. There is also high confidence that benefits will be realised for human health from reducing particles, including black carbon, and to crop yields from reducing tropospheric ozone concentrations.

While many of the measures identified by the study are already available and being implemented by some countries, a considerable amount of work will need to be done if these measures are to be implemented on a international level.

A government may ban the burning of agricultural waste burning however enforcement of the ban is a different issue. In developing countries where there is limited resources they may not have he man power to enforce such measures the same could be said for the use of cleaning burning stoves.

Fearful that the focus on short-lived climate gases will deter from the current GHG reductions efforts, the UNEP/WMO study warns that deep and immediate carbon dioxide reductions are still required to protect against long-term climate.

The measures identified by the study complement but do not replace anticipated carbon dioxide reduction measures. For major carbon dioxide reduction strategies target the energy and large industrial sectors and therefore would not necessarily result in significant reductions in emissions of black carbon or the ozone precursors methane and carbon monoxide.

As with many environmental problems, we know the cause, we the know the effects and we know the solutions but we are still faced with the barriers of political apathy and public resistance that stifles progress in resolving the problem.

The study clearly demosntrates the benefits of taking action on black carbon and ground-level ozone (and its precursors) have of a number climate change, public health and food security benefits especially in developing countries where health and food are high priorities.

All we need now is to put what we know into practice.

© Gary Haq 2011

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Is Clean Air Bad for the Planet?

HEALTH damaging particles in polluting gases emitted by industry, traffic and domestic heating have a ‘cooling’ effect on the climate. In reducing local air pollution we are lowering this cooling effect and inadvertently accelerating global warming. Is clean air bad for the planet?

Gary Haq HEALTH damaging particles in polluting gases emitted by industry, traffic and domestic heating have a ‘cooling’ effect on the climate. In reducing local air pollution we are lowering this cooling effect and inadvertently accelerating global warming. Is clean air bad for the planet?
The burning of fossil fuels such as coal and oil emit gases with small particles known as aerosols. These aerosols include PM10 and sulphates and are found in motor vehicle emissions as well as industrial and domestic heat emissions. They have been linked to asthma, heart problems, lung cancer and premature death as well as having an impact on ecosystems. Aerosols influence the nature of clouds and play a key role in reflecting incoming solar radiation and reducing temperatures at the earth’s surface. They mask the earth from the effects of global warming. While there is still scientific uncertainty about the contribution of this group of air pollutants to ‘climate cooling’ there is an urgent need to reduce the concentrations of these small particles to protect human health and environment.

The World Health Organization (WHO) estimates that outdoor air pollution is responsible for 600,000 premature deaths worldwide each year. Britain is one of ten European Union member states that have recently been warned over excessive levels of PM10. The UK together with Cyprus, Estonia, Germany, Italy, Poland, Portugal, Slovenia, Spain and Sweden could face court action if it fails to meet a European directive limiting these harmful airborne particles. In particular, developing cities in Asia and Africa are struggling with a rapid growth in traffic, urban expansion and industrial development. This has resulted in high levels of polluting air emissions and poor air quality.

Gary Haq In many large Asian cities you will find street hawkers sitting beside strategic road junctions experiencing the general hustle and bustle of daily life. However these individuals are being exposed to high concentrations of motor vehicle pollutants increasing the risk of developing respiratory disease and cancer. Children ill with respiratory disease caused by exposure to high concentrations of air pollutants will be children that will not learn very well, will suffer in adult life from low levels of qualifications and skills which in turn has implications for their quality of life and the economic development of the country as a whole.

The issue of local environmental quality versus global environmental pollution poses an interesting ethical dilemma. Policies to reduce local air pollution such as improving vehicle technology, installing clean technologies in polluting industrial plants and introducing low-sulphur fuels will protect the health of many urban residents. However, by reducing aerosols emissions we are reducing their climate cooling effect. This could speed up global warming and climate change and thus threatens the lives of 7 billion people on the planet.

Gary HaqIf we are to avoid the inadvertent warming resulting from a reduction in PM10 and sulphate aerosols then we need to reduce ‘short-lived’ climate warming gases. That is the view of the Global Atmospheric Pollution Forum – an international partnership of governmental and non-governmental organisations that address air pollution. Unlike carbon dioxide, a key greenhouse gas that remains in the atmosphere for up to 100 hundred years, black carbon, ground-level ozone and methane are substances that have a relatively short-life in the atmosphere, lasting from days to weeks in the case of ozone and black carbon and for a decade with regard to methane. Black carbon is emitted from diesel engines, while ground-level ozone is produced from the reaction of gases from vehicle exhaust, industrial emissions, and chemical solvents. These pollutants are both local air pollutants as well as climate warming gases. While methane is an ingredient needed for the formation of ground-level ozone. Therefore decreasing the concentrations of these gases by cutting emissions could produce relatively quick climate results. This would counteract the cooling effect caused by a reduction in other pollutants such as PM10 and sulphates needed to protect human health. Measures to reduce concentrations of ground-level ozone, black carbon and methane must be pursued alongside cuts in carbon dioxide emissions. This approach should to be addressed in future climate change negotiations. A global assessment of short-lived pollutants is required to feed into the policy process.

It is clear air pollution and climate change are intimately linked with regard to sources and effects on human health and environment. Actions taken to reduce emissions of traditional pollutants may increase or decrease emissions of greenhouse gases. Likewise, strategies to reduce greenhouse gases can have positive or negative effects on air pollution. If we are to develop effective air pollution prevention policies then we to need an integrated approach to address both local air pollution and climate change. This means abandoning the traditional view of the environment as being made up of separate parts and treating it as a functioning interrelated system.

By taking a holistic view of air pollution and climate change we can ensure that clean air will never be bad for the planet.

© Gary Haq 2009