Climate change is a global problem that demands a global solution. The United Nations has been at the forefront in assessing the science and forging a political solution. The Intergovernmental Panel on Climate Change, which brings together 2,000 leading climate change scientists, issues comprehensive scientific assessments every five or six years: in 2007, it concluded with certainty that climate change was occurring and that human activities were a primary cause. The 192 members of the UN Framework Convention on Climate Change are negotiating a long-term agreement that would both guide countries in reducing emissions that contribute to climate change and help countries adapt to its effects. The UN Environment Programme (UNEP) and other UN agencies have been at the forefront in raising awareness.

The UN helps developing countries to respond to the challenges of global climate change. Twenty-seven UN agencies have formed a partnership to deal comprehensively with the problem. For instance, the Global Environment Facility, which brings together the UN Development Programme, the UN Environment Programme and the World Bank, funds projects in developing countries. As the financial mechanism of the Climate Convention, it allocates about $250 million per year in projects on energy efficiency, renewable energies and sustainable transportation.

The United Nations is working to solve global environmental problems. As an international forum for building consensus and negotiating agreements, the UN is tackling global problems like climate change, ozone layer depletion, toxic waste, loss of forests and species, and air and water pollution. Unless these problems are addressed, markets and economies will not be sustainable in the long term, as environmental losses are depleting the natural "capital" on which growth and human survival are based.

The UN Environment Programme (UNEP) and the World Meteorological Organization (WMO) have been instrumental in highlighting the damage caused to Earth's ozone layer. As a result of a treaty known as the Montreal Protocol, Governments are phasing out chemicals that have caused the depletion of the ozone layer and replacing them with safer alternatives. This will spare millions of people from contracting skin cancer because of exposure to increased ultraviolet radiation.

During the first UN decade on water (1981-1990), more than a billion people gained access to safe drinking water for the first time in their lives. By 2002, another 1.1 billion people had clean water. In 2003, the International Year of Freshwater raised awareness of the importance of protecting this precious resource. The second international water decade (2005-2015) aims to reduce by half the number of people without a source of clean drinking water.

Seventy per cent of the world’s major commercial fish stocks are exploited to their sustainable limits or beyond. FAO monitors global fisheries production and the status of wild fish stocks and works with countries to improve the management of fisheries, stamp out illegal fishing, promote responsible international fish trade and protect fragile species and environments.

The Stockholm Convention on Persistent Organic Pollutants seeks to rid the world of some of the most dangerous chemicals ever created. Ratified by 150 countries, the Convention targets 12 hazardous pesticides and industrial chemicals that can kill people, damage the nervous and immune systems, cause cancer and reproductive disorders and interfere with child development. Other UN conventions and action plans help to preserve biodiversity, protect endangered species, combat desertification, clean up seas and curb cross-border movements of hazardous wastes.