Svante Arrhenius, Swedish physical chemist, discovers a direct correlation between Earth’s temperature and carbon dioxide emissions. He calculates that if the atmospheric concentration of carbon dioxide (CO2) were to double, global temperature would rise 4 to 6°C. 

Charles Fabry, French physicist, discovers the ozone layer in the upper atmosphere.   

G. S. Callendar, British scientist, states that the increasing concentration of carbon dioxide (CO2) in the atmosphere derived from human activities is causing Earth’s warm-up 

Roger Revelle and Hans Suess, scientists with the Scripps Institute of Oceanography, demonstrate that the atmospheric concentration of carbon dioxide had increased, meaning that the oceans were not absorbing CO2 emissions as much as it was thought.     

Dr. David Keeling, scientist of the Scripps Institution of Oceanography, begins measuring the amount of carbon dioxide in the atmosphere at the Mauna Loa Observatory in Hawaii. Since then, carbon dioxide levels in the atmosphere have risen by more than 15%.   

Based on the first reliable computer simulation, scientists warn that excess carbon dioxide is causing a greenhouse effect.  

Scientists identify chlorofluorocarbons (CFCs), methane, and nitrous oxide as greenhouse gases.  

Scientist discover that freons used as refrigerants and spray propellants are found to destroy the atmospheric ozone layer.

The First World Climate Conference, recognizing the need to understand the potential serious global problem of human-induced impacts on the climate system, the Conference recommended the creation of a World Climate Program (WCP)   

An international conference is held in Villach, Austria, sponsored by the United Nations Environment Program (UNEP), the World Meteorological Organization (WMO), and the International Council of Scientific Unions. The conference report warns that future climate change is probable and seems to be inevitable due to past emissions, and that a global climate convention should be adopted.       

The ozone hole over Antarctica is first detected.

Analyzing an ice core from Antarctica, scientists demonstrate a close connection between atmospheric concentrations CO2 and Earth’s temperature in the last 100,000 years. 

UN General Assembly addresses climate change for the first time and approves resolution recognizing “that climate change is a common concern of mankind, since climate is an essential condition which sustains life on earth”.

The WMO and UNEP establish the Intergovernmental Panel on Climate Change (IPCC), composed by renowned experts on climate change from around the world, to assess scientific, technical and socio-economic information relating to climate change.

The “World Conference on the Changing Atmosphere: Implications for Global Security" is held in Toronto, Canada. The conference call for the development of a comprehensive framework convention on the atmosphere.

IPCC releases its First Assessment Report on global climate change at a meeting in Sundsvall, Sweden. The report concludes that global mean temperatures could increase by 0.3° Celsius if CO2 emissions do not decreased and recommends the launch of negotiations on a global climate change agreement.

In the Second World Climate Conference, held in November, delegates call for the launch of negotiations. The Ministerial declaration states that "the potential impact of such climate change could pose an environmental threat of an up to now unknown magnitude ... and could even threaten survival in some small island States and in low-lying coastal, arid and semi-arid areas" (A/45/696/Add.1, annex III, preamble, paragraph 2). The conference also called for a comprehensive and dedicated climate observing system.

UN General Assembly establishes the International Negotiation Committee for a Framework Convention on Climate Change. The Committee should negotiate a convention containing “appropriate commitments” in time for signature in June 1992 at the UNCED.

The International Negotiation Committee for a Framework Convention on Climate Change meets for the first time.

The UN Framework Convention on Climate Change is adopted in May 9^th. It is later signed by 155 nations at the Earth Summit in Rio de Janeiro, Brazil.

The United Nations Framework Convention on Climate Change is ratified by more than 50 nations, entering into force on March 21^st.

The First Session of Conference of the Parties (COP-1) is held in Berlin, launching negotiations on a “protocol or another legal instrument”. The Berlin Mandate is adopted in order to strengthen the Convention’s commitments and results in the adoption of the Kyoto Protocol in 1997.     

The IPCC releases its Second Assessment Report on climate change. The report concludes that there still are many scientific uncertainties, yet "…the balance of evidence suggests a discernible human influence on global climate."   

The Second Session of Conference of the Parties (COP-2) is held in Geneva. The Geneva Ministerial Declaration endorses IPCC’s Second Assessment Report conclusions and calls “for the acceleration of negotiations on the text of a legally binding protocol or another legal instrument for appropriate action by the developed country-parties beyond the year 2000” (FCCC/SBI/1997/4).

La Tercer Sesión de la Conferencia de las Partes (COP3) adoptó el Protocolo de Kyoto a la The Third Session of Conference of the Parties (COP-3) adopts the Kyoto Protocol to the UN Framework Convention on Climate.

The Kyoto Protocol is opened for signature on March 16^th.

The Fourth Session of Conference of the Parties (COP-4) adopts the “Buenos Aires Plan of Action” seeking to strengthen the implementation of the Convention and prepare for the Kyoto Protocol’s entry into force.

The Fifth Session of Conference of the Parties (COP-5) is held in Bonn working towards the fulfillment of the Buenos Aires Plan of Action.

The Sixth Session of Conference of the Parties (COP-6) will be held in The Hague, Netherlands, from 13-24 November. COP6 Official Web Site: http://cop6.unfccc.int/.      

First commitment period under the Kyoto Protocol.