Continued warming of the Arctic could lead to global weather changes and flooding that affects one-quarter of the world's people, finds a new report by the global conservation organization WWF.
The report was released in Geneva at the World Climate Conference-3, hosted by the World Meteorological Organization. Some 2,000 delegates are meeting to lay the groundwork for a global system of climate change forecasting.
Arctic air temperatures have risen by almost twice the global average over the past several decades, according to the peer-reviewed scientific report, which warns that further warming could release more greenhouse gases now trapped in the Arctic's frozen soil.
The combination of thawing Arctic sea ice and melting ice sheets in Greenland and West Antarctica is likely to raise global sea levels by about 1.2 meters (four feet) by 2100, more than previously thought, the report warns.
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.
Black carbon is emitted by the burning of forests, savannas and crop residues, by the inefficient burning of biomass and dung for cooking and by diesel engines and coal-fired power stations.
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.
Black carbon's likely near-term climate change contribution ranges from 20 plus percent to up to 50 percent of the CO2 warming effects, according to various researchers. 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.
Another study by the Massachusetts Institute of Technology estimates that five percent 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 percent.
Tropospheric ozone, which occurs from the ground up to 15 kilometers 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 to 20 percent of the CO2 warming.
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.