1894-95
Attempting to explain the ice ages, Swedish scientist Svante Arrhenius theorizes that changes in carbon-dioxide levels in the atmosphere may alter our climate. "It is unbelievable," Arrhenius notes, "that so trifling a matter has cost me a full year."
1905
The word smog, an amalgam of smoke and fog, is coined in England. It doesn't achieve wide currency until after 1950, when motorized transport becomes common in cities.
1938
British engineer G.S. Callendar studies historic temperature and atmospheric CO{-2} concentrations and concludes that the world is warming, fuelled by greenhouse gases.
1948
Al-Ghawar, the world's largest oil field, is discovered in Saudi Arabia. The find leads to a drop in energy prices and a burst of energy intensification in the Western world. By 1950, global energy consumption surpasses 20 billion megawatts, reflecting the rapid expansion of fossil-fuel use.
1957
American oceanographer Roger Revelle - later dubbed "the grandfather of the greenhouse effect" - concludes that we are undertaking a "large-scale geophysical experiment" by releasing CO{-2} into the environment. (Mr. Revelle goes on to teach at Harvard University, where his views have a significant effect on his students, who include a young Al Gore.)
1970
New York's Fifth Avenue is shut down as 20 million Americans celebrate the first Earth Day and the arrival of a global environmental movement.
1979
University of Toronto meteorologist Kenneth Hare co-ordinates a summary paper for the first World Climate Conference in Geneva. The reaction from politicians? "Little or none," Mr. Hare later comments.
1983
Two American scientific reports predict that the Northwest Passage will open to ships during the summer and the Hudson Bay lowlands will become a "food basket" within a decade.
1985
Sharp seasonal reductions in the Earth's stratospheric ozone layer, which protects life from harmful ultraviolet radiation, are detected by British scientists.
1987
In the Montreal Protocol, 24 nations agree to limit the production of chlorofluorocarbons (CFCs). Subsequent accords tighten the agreements, slowing the deterioration of stratospheric ozone.
1988
Scientists at an international climate conference in Toronto announce "warming due to greenhouse gases has begun," and call for a 20-per-cent reduction in CO{-2} emissions by 2005. The eighties become the hottest decade on record.
1989
Bill McKibben publishes The End of Nature, the first major popular book on climate change.
1990
Global energy use surpasses 80 billion megawatts, reflecting the spread of high-energy societies beyond Europe and North America. Newly elected U.S. president George W. Bush warns against global-warming policies that affect economic growth.
"This is not a disaster, it is merely a change. The area won't have disappeared, it will just be under water. Where you now have cows, you will have fish." - A member of the U.S. delegation at a climate-change conference addresses the topic of flooding and Bangladesh.
1991
Fearful that their nations will disappear under the waves as seas rise, the 15 member countries of the South Pacific Forum petition industrialized nations to cut emissions of greenhouse gases.
A strategy memo from the U.S.-based Global Climate Coalition identifies the goal of the industry-funded group (which includes Exxon and Shell) as to "reposition global warming as theory rather than fact."
1992
At the United Nations' Earth Summit in Rio de Janeiro, more than 150 countries agree to set individual non-binding limits on greenhouse-gas emissions.
1994
Scientists report a 65-to-70-per-cent decrease in the ozone layer over the Faraday research base in Antarctica, further evidence of a long-term erosion of this section of the Earth's atmosphere.
1995
The Intergovernmental Panel on Climate Change declares that "the balance of evidence suggests a discernible human influence on global climate" and predicts global temperatures will rise by up to 3.5 degrees Celsius by the end of the 20th century.
1997
Industrialized nations, including Canada, agree to legally binding emissions cuts under the Kyoto Protocol. The U.S. refuses to ratify the Kyoto accord without "meaningful participation" from developing nations.
1998
A 200-square-kilometre chunk of ice splits from the Larsen B ice shelf in Antarctica. 1999
George Monbiot, British commentator and author of the climate change book Heat, offers a stinging indictment of air travel and its massive carbon footprint: "Flying across the Atlantic is as unacceptable, in terms of its impact on human well-being, as child abuse," he writes in a column in The Guardian.
2000
Robins and barn swallows appear for the first time in Sachs Harbour, NWT, one of Canada's most northern communities. "We can't read the weather like we used to," an Inuit resident says. "And it's changing our way of life."
2001
A 2,600-page report from the Intergovernmental Panel on Climate Change states that the Earth is warming faster that at any time during the past 1,000 years and that concentrations of CO{-2} possibly have not been higher for 20 million years.
2001
The governor of Arkansas appears on the CBC's This Hour Has 22 Minutes to comment on plans to protect Parliament from global warming with a refrigerated dome: "Hi, I'm Mike Huckabee ... wanting to say congratulations, Canada, on preserving your national igloo!"
2002
The Canadian Parliament ratifies the Kyoto climate-change accord, while Australia and the U.S. balk. "It's a great day today. I'm passing Kyoto," prime minister Jean Chrétien says. "All you guys some weeks ago were telling me I was going to hit the wall."
2003
A conflict over water in Darfur, Sudan, between the Sudan Liberation Army and the Justice and Equality Movement, is identified as the first war directly attributable to climate change.
The so-called hockey-stick graph representing rising temperatures in the Northern Hemisphere during the past millennium is released. A nasty fight over the veracity of the data ends in 2006 when the U.S. National Research Council, at the request of Congress, supports the findings.
2004
The Day After Tomorrow, a movie based on a climate-change disaster, is released - and reportedly generates 10 times the media coverage as the IPCC's 2001 report.
Walruses, polar bears and some species of seals could be extinct by the end of the century. That's the dire prediction of the eight-nation Arctic Climate Impact Assessment, which finds that climate change disproportionately affects the North.
2005
British scientist James Annan bets two Russian climate skeptics $10,000 (U.S.) that global temperatures will increase during the next decade.
The European Union Emission Trading Scheme, a "cap and trade" system that allows polluters to buy carbon credits for excess greenhouse-gas emissions, opens for business on Jan. 1 and handles €7.2-billion in trades during its first year.
The Kyoto Protocol becomes international law on Feb. 16, but Canada's federal government - now led by Stephen Harper's Conservatives - has yet to introduce a plan to meet the required 6-per-cent reduction in greenhouse-gas emissions.
2006
An Inconvenient Truth, Al Gore's hard-hitting documentary about global warming, opens at the Sundance Film Festival and goes on to become a worldwide hit, grossing about $50-million (U.S.). Critics maintain the film contains 35 scientific errors.
British economist Nicholas Stern releases his highly influential 700-page report on the economics of climate change. In it, he suggests that 1 per cent of global gross domestic product should be invested annually to avoid the worst effects of climate change, and that failure to do so could cost 5 to 20 per cent of global GDP. (In 2008, he revises the 1 per cent figure to 2 per cent.)
2007
Green Party Leader Elizabeth May calls PM Stephen Harper's failure to meet Canada's Kyoto obligations "a grievance worse than Neville Chamberlain's appeasement of the Nazis."
2007
In April, the UN Security Council convenes to talk about climate change for the first time.
The fourth IPCC report warns that "anthropogenic warming could lead to some impacts that are abrupt and irreversible" and estimates the cost of stabilizing greenhouse gases at $1,830-billion (U.S.) - or roughly France's annual GDP.
2008
The World Conservation Union releases a report stating that one-quarter of all mammals could become extinct because of climate change. The U.S. Department of the Interior adds polar bears to its list of endangered animals in May - the first listing directly related to climate change.
2009
Italy and Switzerland agree in March to examine how to redraw their border as glaciers that once guided politicians and mapmakers melt.
In September, Greenpeace activists successfully shut down Shell's Albian Sands mine in Fort McMurray for 30 hours to protest against the environmental impact of Alberta's oil sands.
In November, after hackers make public thousands of e-mails from Britain's leading climate research institute, climate skeptics say the correspondence is proof of a conspiracy among scientists to distort climate data.