Media playback is unsupported on your device Media caption How solar stoves can reduce the amount of smoke produced during cooking

The US Secretary of State Hillary Clinton has announced a global partnership to tackle the scourge of toxic smoke from indoor cooking fires.

Cooking smoke is estimated to shorten the lives of 1.9 million people a year; it also contributes to climate change.

The Global Alliance for Clean Cookstoves is a partnership between the US government and other nations along with charitable foundations.

It is believed to be the first major attempt to tackle the issue worldwide.

The project will attempt to build on national programmes already underway in India, Mexico and Peru.

It aims to introduce modern low-pollution stoves to the homes of 100 million poor people by 2020.

Clean stoves run on biomass (with chimneys and clean-burn mechanisms), or gas, or on solar power.

The stoves programme would help to protect poor people from eye disease, lung disease and cancer; save forests from being ravaged for fuel; reduce CO2 emissions and reduce emissions of black smoke, which also contributes to global warming.

But it is a huge challenge for a global partnership to deal with the scattered homes of the estimated 3 billion poor people who cook on stoves or open fires.

The Alliance is co-ordinated by the UN Foundation. The US government is pledging $50m, with other partners adding a further $10m over five years. More funds are being sought to expand the scheme.

Finance from carbon trading has not so far been used for cookstoves, even though it would be a highly effective way of combating climate change.

There has been wrangling over the rules of the Clean Development Mechanism, which refuses funding for projects that might have happened otherwise.

Typically carbon finance has tended to favour big projects anyway, which has made it hard for the sort of small-scale packages with tailor-made cooking solutions in poor nations.

Cooking is estimated to produce about 20% of the world's emissions of black carbon. The main sources of black carbon are forest burning and incomplete combustion of fossil fuels like coal and diesel, but cookstoves are a particular problem in Asia.

The role of black carbon in climate change is still being quantified and will be the source of debate for the next IPCC report. Some scientists believe it is the second largest contributor to climate change after CO2, with upper estimates suggesting it could be responsible for as much as 55% of the warming from CO2.

In areas covered in snow and ice where albedo - reflectivity - is reduced by deposits of atmospheric carbon, it may equal the warming effect of CO2.

The clean cookstoves programme also claims less obvious benefits: collecting biomass for cooking and heating forces women and children to spend hours each week collecting wood. Women face severe per­sonal security risks as they forage for fuel, especially from refugee camps and in conflict zones.

Cooking with wood also increases pressure on habitats and wildlife.