Level of carbon dioxide gas (CO2) in the atmosphere, as later measured in ancient ice, is about 280 ppm (parts per million). Average global temperature is reckoned to be about 13.5°C. The is the "pre-industrial" baseline for all discussions of the impact of human activity on the atmosphere and climate.
1800 - 1870
First stage of the Industrial Revolution. Coal, railroads, and land clearing speed up greenhouse gas emission, while better agriculture and sanitation speed up population growth.
French polymath Jean-Baptiste Fourier calculates that the average temperature on Earth would be much colder (below freezing) if it wasn't for the planet's atmosphere trapping some of the Sun's energy and stopping it escaping back into space. He likens the effect what happens to air in a box with a glass lid.
Irish physicist John Tyndall discovers that carbon dioxide and water vapour in the atmosphere absorb heat that would otherwise radiate back into space. He predicts that an increase in the amount of such gases in the atmosphere would lead to rising temperatures and climate change.
A pub in his hometown of Carlow, a crater on Mars, a mountain in the Sierra Nevada, an asteroid, a peak on the Matterhorn and research institutes in Manchester and Cork have all been named after Tyndall.
Wikipedia photo: http://en.wikipedia.org/wiki/Image:Tyndall_John_standing.jpg
Second stage of the Industrial Revolution. Fertilizers and other chemicals, electricity, and public health further accelerate economic growth.
Swedish scientist Svante Arrhenius is the first to propose a human influence on the climate change. He predicts that the CO2 released from the burning of fossils fuels would trap more heat in the Earth's atmosphere. He reckons a doubling of the amount of CO2 could lead to a 4 - 5C rise in global temperatures, not far off what modern scientists have calculated with computer modelling.
It was Arrhenius who described Fourier's findings as the atmosphere acting "like the glass of a hothouse".
Wiki photo: http://upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Arrhenius2.jpg/180px-Arrhenius2.jpg
Opening of the Texas and Persian Gulf oil fields heralds era of cheap and plentiful fossil-fuel energy,
British engineer Guy Stewart Callendar calculates from observed temperature records around the world that temperatures had risen by half a degree Celsius between 1890 and 1935. He also discovers that CO2 levels had risen by 10 per cent in the same period and hypothesizes that rising CO2 is causing the temperature to rise. Most meteorologists are sceptical.
Callendar graph: http://www.aip.org/history/climate/images/callendar.jpg
1940 to 1970
A worldwide cooling of 0.2°C is recorded. This is later explained as the result of the build up of particulate pollution in the atmosphere (such as sulphate aerosols) from increasing industrial activity after WWII. This pollution prevented some of the Sun's energy from reaching the Earth. As industries clean up their act in the 1970s and 80s this "global dimming" effect ceases.
Good graph: http://upload.wikimedia.org/wikipedia/en/a/a2/Climate_Change_Attribution.png
Canadian physicist Gilbert Plass proves that proves that increased levels of carbon dioxide can increase atmospheric temperature. Austrian chemist Hans Seuss detects the carbon dioxide released into the atmosphere by burning fossil fuels.
US oceanographer Roger Revelle discovers that the oceans will not, as had been assumed, be able to absorb the bulk of the CO2 human activity was producing and concludes that humanity is conducting a "large-scale geophysical experiment" on the planet.
Charles David Keeling is hired by Revelle and Seuss to make precise measurements of CO2 in the atmosphere at Mauna Loa in Hawaii. The level is 315 parts per million (ppm). Mean global temperature (five-year average) is 13.9°C. He soon discovers a clear upward trend in CO2 levels. His findings become known as the Keeling Curve. Observations continue in Hawaii and in June 2008 the CO2 level reaches 385 ppm.
In the mid-sixties Revelle shows the curve to a small undergraduate class which includes one Al Gore, sparking his lifelong interest in the issue.
Keeling curve: http://upload.wikimedia.org/wikipedia/commons/thumb/5/51/Mauna_Loa_Carbon_Dioxide-en.svg/800px-Mauna_Loa_Carbon_Dioxide-en.svg.png
The global mean surface temperature averages 14°C, half a degree above pre-industrial levels. This 30 year period is taken as an approximation of the Earth's climate for purposes of comparing with present trends.
The Arab oil embargo produces the first big energy crisis in the industrialized world. A series of reports by the US Department of Energy in the 1970s increase concern about future global warming.
The first complex and plausible computer models of the global climate show a warming of several degrees if there is a doubling of pre-industrial levels of carbon dioxide in the atmosphere.
Geneva, Switzerland. The first World Climate Conference brings together a range of scientists. They strengthen the coordination of their research efforts and call on Governments to "foresee and prevent potential man-made changes in climate that might be adverse to the well-being of humanity".
A report from the US National Academy of Sciences concludes that that doubling CO2 will bring 1.5-4.5°C global warming and warns that "A wait-and-see policy may mean waiting until it is too late" to avoid significant climate changes.
Villach, Austria. An international conference of climate scientists reach a consensus, concluding that the increased levels of greenhouse gases already in the atmosphere will "in the first half of the next century, cause a rise of global mean temperature which is greater than any in man's history" . They urge governments to consider an international treaty to restrict emissions.
The warmest year to date since records began. Three years later the 1980s are confirmed as the warmest decade to date, with seven of the eight warmest years recorded up to 1990. Even the coldest years in the 1980s were warmer than the warmest years of the 1880s.
An ice core from Antarctica analyzed by French and Russian scientists reveals an extremely close correlation between CO2and temperature going back more than 100,000 years.
The Brundtland Commission report defines sustainable development as "meeting the needs of the present generation without compromising the ability of future generations to meet their needs".
Toronto, Canada. A major conference of climate scientists concludes that "Humanity is conducting an unintended, uncontrolled, globally pervasive experiment whose ultimate consequences could be second only to a global nuclear war." They call for an international treaty to reduce emissions by 20% by 2005. In fact global emissions in 2005 are slightly above 1988 levels.
Washington DC, USA, James Hansn of NASA gives his landmark testimony before Congress. He tells Senators that "global warming is at hand" and says he is 99% certain human activity is already changing the climate.
The World Meteorological Organization and the UN Environment Programme establish the Intergovernmental Panel on Climate Change (IPCC) "to provide the decision-makers and others interested in climate change with an objective source of information."
Hannover, Germany. 20 environmentalists from Europe and the US meet to discuss cooperating on climate change. Today the Climate Action Network includes 360 NGOs around the world including Friends of the Earth, Trócaire, Oxfam and Christian Aid.
New York, USA. The UN General Assembly calls for global summit on environment and development issues.
The first report of the IPCC finds that the planet has warmed by 0.5°C in the past century. IPCC warns that only strong measures to halt rising greenhouse gas emissions will prevent serious global warming. This provides scientific clout for UN negotiations for a climate convention. Negotiations begin after the UN General Assembly in December.
Rio, Brazil. The UN Conference on Environment and Development, better known as the "Earth Summit" agrees the UN Framework Convention on Climate Change. The USA is among the 154 countries which signs the treaty but blocks the inclusion of binding targets. The UNFCCC aims to "to achieve stabilization of greenhouse gas concentrations in the atmosphere at a low enough level to prevent dangerous anthropogenic [i.e. human] interference with the climate system"
The hottest year on record to date.
The second IPCC report states that "the balance of evidence suggests a discernible human influence on global climate".
Berlin, Germany. The first Conference of the Parties to the UNFCCC agrees to negotiate binding emission cuts for industrialized countries.
Kyoto, Japan. 164 countries agree the Kyoto Protocol which mandates cuts in emissions by industrialised countries of an average of 5.2% from 1990 levels by 2008-2012. Minister Noel Dempsey signs for Ireland. The EU agrees to cut its emissions by 8%.
Luxembourg. EU environment ministers agree how to share out the emissions target to achieve an overall reduction of 8%. In recognition of its status as one of the poorer countries, EU member states agree that Ireland can in fact increase its emissions by 13% up to 2012.
The hottest year on record to date
Scientists, reconstructing the global climate for the last 1,000 years, using weather records, tree-rings, coral and ice-core readings, declare that the 1990s are the hottest decade at least a millennium.
Ireland publishes its first National Climate Change Strategy.
Washington DC, USA, March. Newly elected U.S. President, George W. Bush, renounces the Kyoto Protocol because he questions the science and he believes it will damage the US economy. The EU vows to press ahead with the ratification of the treaty.
London, UK, September. Third IPCC report states baldly that a level of global warming unprecedented since end of last ice age is "very likely" and that new and stronger evidence suggests it is human induced. Effective end of debate among all but a few scientists.
Marrakesh, Morocco, November. The remaining signatories to the Kyoto Protocol, without the US, agree the detail of how the protocol will work.
Irish emissions reach 27% above 1990 levels, more than twice the 13% increase Ireland is allowed under Kyoto.
EU member states, including Ireland, ratify the Kyoto Protocol. So do Japan and Canada. With the US and Australia opting out the complicated rules mean that Russia must ratify for the treaty to become legally binding.
Europe experiences its hottest summer in 500 years. Over 30,000 people die during the heatwave. Extreme weather costs an estimated record of US$60 billion around the world this year.
The EU and Russia do a deal on Kyoto. The EU will support Russia's bid for membership of the World Trade Organization and in return Russia ratifies Kyoto.
February 16th. More than six years after it was agreed the Kyoto Protocol comes into force with legally-binding emissions targets for developed countries including Ireland.
Mumbai, India, July. 94.4cm of rain falls in a single day, the largest daily rainfall ever recorded in India, wreaking havoc in the country's financial capital. By contrast Dublin averages 73cm in a year! The downpour in Dublin on Saturday August 9th 2008 was 7.6cm.
New Orelans, USA, August. Hurricane Katrina makes landfall. The 2005 Atlantic hurricane season was the most active in recorded history, shattering all previous records. So many storms formed that the US National Hurricane Centre ran out of names for them and was reduced to using letters from the Greek alphabet. Apart from the death and destruction the hurricane season contributed to a shift in US public opinion on climate change.
Montreal, Canada, December. The signatories to the UNFCCC agree to new talks aimed at a deal on what happens after the initial commitments under the Kyoto Protocol expire in 2012.
2005 was the hottest year ever since records began.
Los Angeles, USA, May. Al Gore's film, An Inconvenient Truth, opens. It goes on to become the 4th highest-grossing documentary in US box-office history.
London, UK, October. The government-commissioned Stern Review brands climate change "the greatest market failure the world has seen" and concludes that it is much cheaper to prevent runaway climate change than cope with the consequences.
Dublin, Ireland, June. The Fianna Fail/Green Party Programme for Government commits to reduce Irish emissions by an average of 3% a year, to introduce a Carbon Budget and to put a price on climate pollution with a carbon levy.
Arctic circle, September. Arctic sea-ice reaches its lowest extent ever recorded, with the famous North West Passage becoming ice free for the first time. Scientists who had predicted the Arctic might totally be ice free in summer by mid-century worry it could now happen in less than a decade.
Bali, Indonesia, December. The signatories to the UNFCCC agree to complete negotiations on a post-2012 deal by the time they meet in Copenhagen in December 2009.
2007 ties 1998 as the Earth's second hottest year since record began. The 11 warmest years on record have all occurred in the last 13 years.
Brussels, Belgium, January. The European Commission proposes that Ireland, now one of the richest countries in the EU, should reduce its emissions to at least 20% below 2005 levels in any new global deal.
This timeline was partially based on the following sources:
The American Insititute of Physics http://www.aip.org/history/climate/timeline.htm
Environment Canada http://www.ec.gc.ca/climate/timeline-e.html
Green House Network http://www.greenhousenet.org/resources/timeline.html
Ministry of Enviornment, India http://envfor.nic.in/cc/int_nego/timeline.htm
The New Scientist http://environment.newscientist.com/channel/earth/climate-change/dn9912-timeline-climate-change.html