Over the coming weeks and months, the three Special Envoys on climate change appointed by UN Secretary-General Ban Ki-moon will be making whistle-stop tours of key capital cities to build a solid and sustainable consensus on action over climate change. Gro Harlem Brundtland of Norway, Han Seung-soo of the Republic of Korea and Ricardo Lagos Escobar of Chile underline the seriousness with which the Secretary-General takes the threats, as well as the opportunities presented by the immense challenges documented in the recently published reports of the Intergovernmental Panel on Climate Change (IPCC).

The United Nations is the only forum in which an agreement aimed at reducing greenhouse gas (GHG) emissions beyond 2012 can realistically be brokered among the 190 plus countries with different outlooks and economies but of a common atmosphere. The climate change challenge involves every nation and will, if unchecked, touch every community and citizen on a time-scale of decades rather than centuries.

In 2007, climate change truly became an issue of highest concern to the United Nations, because there is now the full understanding that the phenomenon will fundamentally affect the way the world operates in the twenty-first century -- from health care, aid and water to economic activity, humanitarian assistance, peacebuilding and security concerns. The United Nations has played a pivotal role in building the scientific consensus, raising the issue to the front pages of the world's media and putting it in the in-tray of Heads of State and Government, as well as the chief executive officers of businesses and industries. Since February 2007, the IPCC has published three important reports, and the more than 2,000 scientists and experts of the IPCC have put an end to any doubts in the science debate.

Climate change is happening and the links between rising temperatures and human activities are considered "unequivocal". The IPCC has outlined the likely impacts of climate change in the coming decades if the international community fails to act. These include sea-level rise, which could deprive millions of people from Bangladesh to the small islands of their land and livelihoods, in addition to the melting of mountain glaciers, which are the source of water for millions of people, businesses and farmers around the world. However, the IPCC has also noted other factors that are cause for hope and must be the catalysts for action. The experts in their report issued in May 2007, argued that decarbonizing the global economy to a point where climate change should be manageable could cost 0.1 per cent of global gross domestic product (GDP). Indeed, in some sectors, the actual costs of significantly boosting energy efficiency would actually make rather than cost money for managers and homeowners.

The United Nations, through the UN Framework Convention on Climate Change (UNFCCC), has also been at the cutting edge of assisting in the development of creative new carbon markets. The Kyoto Protocol's Clean Development Mechanism (CDM) allows developed countries to offset some of their emissions through clean and renewable energy projects and certain forestry schemes in developing countries. Over the coming years, the CDM funds flowing from North to South will reach up to $100 billion. New high-technology industries and job opportunities are emerging in both developed and developing countries. China and India are now home to two of the biggest wind turbine and power companies. Investment in renewable energy, driven in part by the UN-brokered climate treaties, is expected to top $80 billion in 2007. It is bringing down costs and increasing opportunities for deployment in rural areas.

The UN system is helping to accelerate this further. The United Nations Environment Programme (UNEP), in partnership with the UN Foundation and Asian banks, has piloted a project that has brought solar power to 100,000 people in India. The idea was to buy down part of the interest rates for loans in order to make them affordable to low-income households. The benefits for the global community may be reduced emissions. But in a world where 1.6 billion are currently without access to electricity, this access to clean power and light is a new and immediate benefit for the local community. Such developments also echo the Millennium Development Goals, as they relate to areas such as poverty eradication, education and health, not the least as a result of lower indoor air emissions that are linked with maternal and childhood diseases and the premature deaths of between 800,000 and up to 2.4 million people.

Climate change also represents opportunities to better manage the world's natural and nature-based resources. The Food and Agriculture Organization of the United Nations (FAO) estimates that 13 million hectares of the world's forests are lost annually and that deforestation accounts for approximately 20 per cent of the global GHG emissions. We undervalue the huge economic importance of forests and ecosystem services -- and biodiversity in general -- but addressing climate change may also recognize some of these issues. Standing forests currently fall outside the carbon markets. A decisive emissions reduction regime beyond 2012 opens up the opportunity to give them greater economic value and thus provide reasons for conservation and sustainable management.

The climate change issue, along with such initiatives as the Global Compact, is assisting the restoration of the relationships between the United Nations and other sectors of society, including business and industry. A fascinating feature of recent months and the past year is a call by the private sector for global international regulation. Globalization had looked to the free market, unfettered by "red tape", as a way of liberating economies. But the reality of climate change has led to a rethinking by the leaders of industry and the financial services sector. Indeed, businesses in many parts of the world are publicly demanding climate-related regulations, guidelines, emission caps, etc., partly because many perceive climate change as an economic risk and also a significant market opportunity, but only if the ground rules are in place and a level playing field is operating.

The missing piece in the jigsaw puzzle is a universal agreement by Governments over the steps needed to reach the 60 to 80 per cent emission cuts that scientists say are required to stabilize the atmosphere. The UN role as an honest broker will be key over the next two years to realizing trust between nations -- trust based on mutual self-interest and a sense that all are acting for a common cause, albeit at different speeds. The elements are already there. The European Union has committed itself to a 20-per cent reduction in GHG emissions by 2020, and up to 30 per cent if others follow. In the United States, there is growing action by cities and states; for example, the Mayor of New York City has announced a pledge to cut the city's GHG emissions by 30 per cent. Also, over 460 mayors in the United States have pledged to cut emissions by 7 per cent below the 1990 levels. California, has announced it will reduce emissions by 25 per cent by 2020.

Rapidly developing economies, such as Brazil, China and India, are carrying out voluntary actions to decrease the levels of emissions in comparison to what they would have been without action. The Chinese authorities estimate that around 7 per cent of China's energy comes from renewable sources, equivalent to an emission savings of 328 million tones of carbon dioxide. Targets have been set for an even higher renewable energy use. China estimates that, by 2010, energy consumption intensity -- a measure of the amount of energy used per unit of GDP -- will have fallen by 20 per cent since 2005. Brazil, where a significant level of emissions comes from land-use change, has reduced deforestation in the Amazon by over 50 per cent over the past three years. Some 80 per cent of all new cars sold in the country are flex-fuel and able to run on petrol or ethanol.

The IPCC estimates that rapidly developing economies have reduced emissions by 500 million tonnes over the past three decades, equating to more than that of the Annex I countries under the Kyoto Protocol. Another way of building trust is through adaptation to climate change, so-called climate proofing of economies from coastal management and health care to agriculture and infrastructure development. This is about good planning as much as financial assistance. Multilateral and bilateral donors, regional development banks and international investment flows into developing countries need to reflect adaptation in their investment decisions.

UNEP and the United Nations Development Programme are piloting adaptation in eight developing countries under the One UN strategy. We should look broadly at what can be done, with the United Nations at the central platform, and welcome all initiatives and paths that contribute to reducing climate change, including voluntary sector initiatives and partnerships. We should also look at how other multilateral environmental agreements contribute to the overall goals.

The Montreal Protocol, which aims to phase out ozone layer depleting gases, has significantly reduced chlorofluorocarbons -- the chemicals once common in products like hairsprays that are linked with climate change. New studies indicate that the offset level of global warming has been four times higher than that envisaged through the Kyoto Protocol. More ozone-friendly chemicals have a climate footprint as well. Scientists estimate that accelerating the phasing out of these chemicals, along with technical measures, could save emissions equivalent to half a gain of the Protocol. The focus on climate change and the work of the three Special Envoys are now geared towards the next climate change conference in Bali, Indonesia in December 2007, where the world will be looking for concrete action.

The United Nations is also looking at its own backyard. The Capital Master Plan for the refurbishment of the UN headquarters in New York is assessing how to factor green measures into the project in order to create a shining example of an eco-friendly building. It is part of a wider assessment of how UN operations, from building to procurement of goods and services, can echo to the sustainability challenge.