Faster action on climate change may be possible if nations combine substantial cuts in carbon dioxide emissions alongside accelerated moves across a suite of other greenhouse gases and pollutants. According to sources here on Saturday, scientists estimate that nearly 50 percent of the emissions, causing global warming in the 21st century, are from non-CO2 pollutants ranging from black carbon and low-level ozone to methane and nitrogen compounds.
These "climate forcers" would 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. The experts observed that many of these non- CO2 gases and pollutants needed to be addressed in their own right because of growing concern over their impact on human health, agriculture and ecosystems such as forests.
"In addition, their climate contribution, there are compelling and abundant economic and environmental reasons as to why some of the non-CO2 pollutants need to be addressed under treaties, such as the United Nations Framework Convention on Climate Change 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," he added.
Researchers cited black carbon from the inefficient burning of bio-mass and dung for cooking and from diesel engines and coal-fired power stations. Other major sources include the burning of forests, savannah and crop residues.
They also said that black carbon was 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. They also put a wide range of figures on black carbon's likely near-term climate change contribution, ranging from 20 plus percent to up to 50 percent of the CO2 warming effects.
"Especially damaging are the black carbon emissions that end up on snow and ice, including the Arctic and Himalayan Tibetan plateau," they added. According to scientists, 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 soyabean crop in China, Japan and the Republic of Korea alone (linked with ground level ozone) may be five billion dollars a year.
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. The contribution of tropospheric ozone to the greenhouse effect could range from 15 percent to 20 percent of the CO2 warming.
Meanwhile, nitrogen compounds, emitted from sources, including animal wastes, sewage, inefficient use of fertilisers 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 fertilising effect.
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