Global Warming

A U.N. conference in Qatar next week is the latest attempt to combat global warming after mounting evidence that human activity is disrupting the climate.

Here is a timeline of the road to action on global warming:

300 BC - Theophrastus, a student of the Greek philosopher Aristotle, documents that human activity can affect climate. He observes that drainage of marshes cools an area around Thessaly and that clearing of forests near Philippi warms the climate.

1896 - Sweden's Svante Arrhenius becomes the first to quantify carbon dioxide's role in keeping the planet warm. He later concluded that the burning of coal could cause a "noticeable increase" in carbon levels over centuries.

1957-58 - U.S. scientist Charles Keeling sets up stations to measure carbon dioxide concentrations in the atmosphere at the South Pole and at Mauna Loa, Hawaii. The measurements have shown a steady rise.

1988 - The United Nations sets up the Intergovernmental Panel on Climate Change (IPCC) to assess the scientific evidence.

1992 - World leaders agree the U.N. Framework Convention on Climate Change, which sets a non-binding goal of stabilising greenhouse gas emissions by 2000 at 1990 levels - a target not met overall.

1997 - The Kyoto Protocol is agreed in Japan; developed nations agree to cut their greenhouse gas emissions on average by at least 5 percent below 1990 levels by 2008-12. The United States stays out of the deal.

2007 - The IPCC says it is at least 90 percent certain that humans are to blame for most of the warming trend of the past 50 years. It also says signs that the planet is warming are "unequivocal".

2009 - A conference of 193 countries agrees to "take note" of a new Copenhagen Accord to fight climate change, after U.N. talks in Denmark. The accord is not legally binding and does not commit countries to agree a binding successor to the Kyoto Protocol when its first stage ends in 2012.

2011 - U.N. climate talks in Durban, South Africa, agree to negotiate a new accord by 2015 that is "applicable to all" and will come into force from 2020.