Scientists estimate that nearly 50 per cent of the emissions causing global warming in the 21 st century are from non-CO2 pollutants ranging from black carbon and low-level ozone to methane and nitrogen compounds.
These ‘climate forcers’ will add to the warming caused by carbon dioxide from the burning of fossil fuels that have been building up since the Industrial Revolution unless their emissions are also addressed.
Many of these non CO2 gases and pollutants need to be addressed in their own right because of growing concern over their impact on human health, agriculture and ecosystems such as forests.
Achim Steiner, UN Under-Secretary General and Executive Director of the UN Environment Programme, said the time had come for further urgent scientific assessments to determine the precise contribution, impacts and the options for action on ‘non-CO2’ pollutants.
“There remains some scientific uncertainty about some of these pollutants’ precise contribution to global warming. But a growing body of science points to a potentially significant role,” he said.
“The international community’s over-arching concern must be to Seal a convincing Deal at the UN climate Convention meeting in Copenhagen in less than 100 days time—one that puts the world on track towards swift and significant cuts in carbon dioxide while also providing the funding to assist vulnerable countries and communities to adapt,” said Mr Steiner, speaking on the margins of the 3rd World Climate Conference, hosted by the World Meteorological Organisation.
“It is also becoming clear that the world must also deploy all available means to combat climate change. At this critical juncture, every transformative measure and no substance contributing to climate change should be overlooked,” he added.
Drew Shindell, a leading climatologist with the NASA’s Goddard Institute for Space Studies, and a lecturer in the Department of Earth and Environmental Sciences at Columbia University New York, said: “By including black carbon and tropospheric ozone precursors in climate mitigation strategies, alongside the longer-lived greenhouse gases, development strategies that are both more effective and less costly can be developed”.
“The UN Environment Program should be congratulated for raising these issues and calling for action. The science supporting the strong role of these pollutants in climate change and in damage to human and ecosystem health is becoming increasingly strong,” added the scientist who has also been a reviewer of the assessments of the Intergovernmental Panel on Climate Change (IPCC) and whose science has been used extensively by the panel.
Experts say that in addition their climate contribution, there are compelling and abundant economic and environmental reasons why some of the non-CO2 pollutants need to be addressed under treaties such as the UN Framework Convention on Climate and its Kyoto Protocol, the Montreal Protocol on Substances that Deplete the Ozone Layer, and regional health agreements, national air quality strategies and voluntary initiatives.
Mr Steiner cited black carbon from the inefficient burning of biomass and dung for cooking and from diesel engines and coal-fired power stations. Other major sources include the burning of forests, savannas and crop residues.
Black carbon is among a suite of air pollutants linked to 1.6 million to 1.8 million premature deaths annually as a result of indoor exposure and 800,000 as a result of outdoor exposure.
Researchers have also put a wide range of figures on black carbon’s likely near-term climate change contribution, ranging from 20 plus per cent to up to 50 per cent of the CO 2 warming effects. Especially damaging are the black carbon emissions that end up on snow and ice, including the Arctic and Himalayan Tibetan Plateau.
Tropospheric ozone including near-surface ozone is a major greenhouse gas, harms human health and is linked to significant damage to crops and ecosystems.
A regional assessment report by the UNEP Project Atmospheric Brown Cloud cited annual losses from the wheat, rice, corn and soya bean crop in China, Japan and the Republic of Korea alone—linked with ground level ozone—may be $5 billion a year.
Another study by the Massachusetts Institute of Technology estimates that five per cent of cereal production in the United States is lost to ground level ozone and that by 2100 crop yields globally could be cut by 40 per cent.
Up to a fifth of all summer-time hospital visits in the north-eastern United States related to respiratory problems are linked to low level ozone, sometimes referred to as smog.
Researchers at the University of Illinois are suggesting that tree growth in the United States is some seven per cent less and that this will climb to up to 17 per cent less by 2100 as a result of low level ozone pollution.
Tropospheric ozone, which occurs from the ground up to 15 kilometres in altitude, is generated by substances such as carbon monoxide and nitrogen oxides mixing with emissions of petroleum products like volatile organic compounds and solvents in the presence of sunlight.
Researchers estimate that the contribution of tropospheric ozone to the greenhouse effect could range from 15 per cent to 20 per cent, of the CO 2 warming.
Meanwhile nitrogen compounds, emitted from sources including animal wastes, sewage, inefficient use of fertilizers, sewage and vehicle emissions are being linked to a wide range of impacts and not just climate change.
The rising number of dead zones—deoxygenated areas of seas and oceans—is raising concern over already vulnerable and depleted fish stocks. Meanwhile nitrogen compound emissions are also contributing to changes in vegetation and ecosystems as a result of their artificial fertilizing effect.
Mr Steiner, speaking less than 100 days before the crucial UN climate convention meeting in Copenhagen, said: “While carbon dioxide can remain in the atmosphere for centuries, some of these other pollutants such as black carbon and ozone have relatively short-lives in terms of days, weeks, months or years”.
“Fast action across a broad front could thus deliver some quick wins on health, food security and wider environmental concerns while also making important contributions to advancing the climate change challenge and the achievement of the poverty-related Millennium Development Goals”.
Lessons from the Ozone Layer Treaty
Action under the Montreal Protocol on Substances that Deplete the Ozone Layer to phase-out fluorinated gases such chlorofluorocarbons (CFCs)—substances once common in products such as hairsprays and refrigerators—has underlined the multiple benefits that can occur in a transition to a Green Economy.
CFCs, whose full and final global phase-out along with 95 other chemicals is scheduled for 2010, were identified as the prime culprit behind the destruction of the Earth’s ozone layer—the high-flying protective gassy shield that filters out deadly ultra-violet rays.
In the past few years scientists have also calculated that the phase-out will, between 1990 and 2010, have reduced global emissions by the equivalent of 135 Gigatonnes of CO 2, delaying climate forcing by up to 12 years.
Governments in 2007 agreed to an accelerated freeze and phase-out of CFC replacements—hydrochloroflurocarbons (HCFCs)—specifically for the climate benefits.
Scientists with the Montreal Protocol estimate that this strategy could deliver cumulative emission reductions equal to more than 16 Gigatonnes of CO2 from now up to 2040
Concern is now focusing on another group of fluorinated gases called hydroflurocarbons (HFCs) and finding alternatives to these so they do not now become the replacements for the replacements.
While HFCs do not damage the ozone layer, they are significant greenhouse gases. Under one scenario, they could equal around 45 per cent of total CO2 emissions by 2050.
The UN Framework Convention on Climate Change and the Montreal Protocol are now cooperating to map out the best strategy to meet this challenge.
“The story of the Montreal Protocol underlines how action on one front can deliver benefits on many others—that every dollar spent on phasing-out substances that are damaging the ozone layer and sparing humanity impacts such as increased skin cancer and eye cataract cases, has also been working to address global warming,” said Mr Steiner.
What is it?
This is basically the smoke that comes out of diesel vehicles and biomass burning. It is a pollutant often linked to inefficient burning, its sources ranging from biomass burning (including wood and dung in cooking) to diesel engines and coal-fired power stations.
Unlike CO 2, which can remain in the atmosphere for centuries to millennia, black carbon has a life of few weeks or less
- One study estimates that emissions from transport are responsible for 18.5 per cent of black carbon emissions.
- 26 per cent of emissions are from stoves for heating and cooking with over 40 per cent of this from wood burning; over 20 per cent from coal; 19 per cent from crop residues and 10 per cent from dung.
- Another estimates that 0.1 per cent of black carbon is from power stations. Coal for other industrial uses such as coking may contribute around eight per cent.
What is it doing?
Black carbon is a key component of air pollution.
The World Health Organization estimates that 1.6 million people a year die from indoor air pollution, making it the 8 th most important risk factor.
- In India it may be responsible for an estimated 3.5 per cent of the disease burden and in African countries such as Mali, Malawi and Rwanda, the figure rises to five per cent.
- An additional 800,000 premature deaths are caused each year by urban air pollution with black carbon and tropospheric ozone key components.
Climate Change Links
Research indicates that black carbon in the atmosphere absorbs heat.
The UNEP Atmospheric Brown Cloud (ABC) project, led by Professor Ramanathan of the Scripps Institution of Oceanography in La Jolla, California, suggests that these brown clouds—which include black carbon—are playing a major role in the observed retreat of the glaciers in the Hindu Kush-Himalayan-Tobetan region.
In addition the ABC study suggests that solar heating of the atmosphere by black carbon and dimming at the surface by black carbon and other pollutant particles are altering weather patterns in Asia, including:
- Triggering significant drying in northern China and increased risk of flooding in southern China and an overall decrease in monsoon precipitation over India and Southeast Asia by between five and seven per cent since the 1950s.
- Since the 1950s the Indian summer monsoon is not only weakening but shrinking with a decrease in early and late season rainfall and a decline in the number of rainy days.
- Decreased reflection of solar radiation by snow and ice due to increasing deposits of black carbon is emerging as another major contributor to the melting of ice and snow.
The precise contribution to climate change is subject to a great deal of investigation and, as with all the non-CO 2 pollutants, the role of other substances and the historical contribution to climate change is different from the contribution to present day changes and for likely future scenarios.
The impact of black soot depositing on ice and snow in places like the Arctic and mountain glaciers, such as those in the Himalayas is also subject to increasing investigation.
One paper in the Journal of Geophysical Research suggests that eliminating black carbon and other organic carbon emissions might reduce net warming in the elevated regions of Eurasia by 20 per cent to 45 per cent over 3-5 years.
Some Possible Actions with Multiple Green Economy Benefits
- Boosting the efficiency of power stations and switching to cleaner and renewable energies will not only cut CO 2 emissions but also reduce black carbon emissions.
Fitting or retrofitting particle traps to diesel vehicles, ideally in combination with the introduction of ultra low sulphur fuels, can also reduce black carbon emissions while improving air quality and public health.
- A paper in August 2009 in Foreign Affairs estimates that fitting particle traps to one million semi-trailer trucks would, over 20 years, yield climate benefits equal to taking over 160,000 trucks or 5.7 million cars off the road.
Mass introduction of more efficient biomass-burning stoves and cookers or introduction of solar cookers would also have multiple benefits.
- Some companies have developed such stoves that cut black carbon emissions by around 70 per cent using passive air flows and better insulation; at the same time, these stoves use 60 per cent less wood, helping to save the forests and reducing CO 2 emissions .
UNEP has just launched an Integrated Assessment of Black Carbon and Tropospheric Ozone to evaluate their role in air pollution and climate change.
Building on the UNEP ABC project, measuring and monitoring of black carbon and other atmospheric particles is to be extended from the Asia-Pacific region across Africa in order to pinpoint ‘hot spots’ where reducing emissions can protect human health.
In addition, UNEP-ABC is sponsoring Project Surya. This aims to reduce black carbon emissions from cooking with biomass and dung in rural India and document its impact on the climate forcing, health and regional climate.
Tropospheric including Low Level Ozone
What is it?
Ozone is a gas that near ground level is considered a pollutant, often times called smog, because it impairs human health and productivity of natural systems such as forests.
Tropospheric ozone refers to the ozone that is present in the atmosphere from the ground up to about 15 km altitude in the Tropics.
In this layer of the atmosphere, most ozone is formed by pre-cursor emissions from the surface, including volatile organic compounds from petroleum products and solvents and others like carbon monoxide from fossil fuel burning.
In the presence of sunlight, these can react to form ozone.
Low level ozone tends to stay locally, whereas higher up it spreads regionally and globally.
Unlike CO 2, which can remain in the atmosphere for centuries to millennia, the pollutants that form ozone persist for hours to months and the ozone formed has a life of just a few days.
What is it doing?
In the European Union more than 21,000 premature deaths annually are associated with ground level ozone according to the European Environment Agency.
It is estimated that in 2000 in the European Union, well over Euro 6 billion-worth of crops were lost due to ozone.
Climate Change Links
The precise contribution of tropospheric ozone to climate change in the 21 st century is, according to some estimates, thought to be equal to between 15 per cent and 20 per cent of that caused by all other greenhouse gases, including CO 2 and black carbon.
Some Possible Actions with Multiple Green Economy Benefits
- Boosting the fuel efficiency of vehicles and moving to plug-in hybrids and electric ones would cut some of the emissions that allow tropospheric ozone to form
- Reducing emissions from a variety of sources including leaks from refineries and petrol stations to paint products, paint shops and dry cleaners
- The reactions that produce the ozone run faster at higher temperatures—some scientists suggest that simple measures to reduce the urban heat-island effect, by for example having white roofs on buildings or more tree planting, could help to reduce the ozone concentration
Methane is a gas emitted naturally from swamps and other wetlands. Human emissions of methane come mainly from landfills and other sources such as oil and gas facilities and livestock. The biggest and growing source is from deforestation, which is contributing up to 20 per cent of emissions.
Methane has an atmospheric life-time of around 12 years, although the precise life-time depends on factors such as temperature and concentrations of other substances.
At the upcoming UN climate convention meeting in Copenhagen, it is hoped that governments will agree to an agreement on Reduced Emissions from Deforestation and forest Degradation (REDD).
This would essentially pay developing countries to conserve forests with the multiple likely benefits of improved water supplies, soil stabilization, reduced losses of biodiversity and employment in resource management and eco-tourism.
UNEP, in cooperation with the UN Development Programme (UNDP) and the Food and Agricultural Organization of the UN with funding from Norway, have launched a UN REDD programme to prepare nine pilot countries for a future REDD arrangement.
Under the Kyoto Protocol’s Clean Development Mechanism, developed countries can invest in off-setting emissions by assisting developing ones to reduce methane emissions from sources such as landfills.
Other options include emissions from untreated sewage and coal mines.
Nitrogen compounds come from a variety of sources including combustion, vehicles, the livestock sector and fertilizer use.
Some contribute to the formation of tropospheric ozone whereas other nitrogen compounds, for example nitrous oxide which has an atmospheric lifetime of about 114 years are greenhouse gases in their own right.
The elevated concentration of nitrous oxide alone contributes about four per cent to climate change
Notes to Editors
The Intergovernmental Panel on Climate Change’s fourth assessment report
The large contribution of projected HFC emissions to future climate forcing
The importance of the Montreal Protocol in protecting climate
Project Atmospheric Brown Cloud
ABC Summary: regional assessment report with focus on Asia
UN Reduced Emissions from Deforestation and forest Degradation
Quantifying the impact of current and future tropospheric ozone on tree biomass, growth, physiology and biochemistry: a quantitative meta-analysis-Global Change Biology
The 3 rd World Climate Conference
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