The first major international agreement, signed by 154 countries at the Rio Earth Summit, was the United Nations Framework Convention on Climate Change (UNFCCC). It was a voluntary "non-binding aim" to reduce atmospheric concentrations of greenhouse gases, with the goal of preventing interference with Earth's climate system.

A particularly significant meeting was held in 1997 Kyoto, Japan. Most industrialized nations agreed to legally binding reductions in greenhouse gas emissions of an average of 6 to 8% below 1990 levels by 2012. This has since proved problematic, especially as the US rejected the Kyoto Protocol in 2001.

	Find out more how the Montreal Protocol is actually working.

Another agreement initiated in 1987 and regularly updated at UNFCC annual meetings is the Montreal Protocol, which aims to stop the use of CFCs and find suitable ‘environmentally’ friendly substitutes. The then general secretary of the UN Kofi Annan described this agreement as "perhaps the single most successful international agreement to date".

In 2007, the Intergovernmental Panel on Climate Change (IPCC) fourth report made convincing reading. Politicians met at the Washington summit in February '07. Representatives from the G8 countries, Brazil, China, India, Mexico and South Africa agreed that developing countries would also have to meet targets for cutting greenhouse gas emissions. This informal meeting also agreed that a global market should be formed to cap and trade carbon dioxide emissions.

In December 2009, despite updated scientific summaries suggesting climate change could be more extreme than thought in 2007, the United Nations Climate Change Conference (UNCCC) ended in failure. Violent clashes between police and protestors outside mirrored verbal clashes between rich and poor countries inside over who should take responsibility for solving climate change. The result was a weak agreement, which scientists say will not cut carbon emissions nearly enough.

The plan had been to create a treaty, binding all countries to cut CO2 emissions quickly. But some rich countries were not yet willing to make cuts as it would threaten their wealth. Other poor countries were unwilling stop burning fossil fuels as to do so would slow up their aims to climb out of poverty. The meeting did however show how complicated it is to get 192 countries to agree and how dependent on oil the world economy has become.

The next UNCCC meeting is due in Novenber 2010 in Mexico. It is likely that there will be intense negotiations between countries this year.