This year’s UN climate conference in Baku, Azerbaijan, marks the world’s 29th leadership gathering to confront global warming since the first “Conference of the Parties” in 1995.
Here are some of the most significant moments in the history of climate talks:
1800s
For about 6,000 years before the industrial era, global levels of atmospheric carbon dioxide (CO2) remained around 280 parts per million (“ppm”). Several European scientists begin studying how different gases trap heat, and in the 1890s Svante Arrhenius of Sweden calculates the temperature effect from doubling atmospheric CO2 levels, demonstrating how burning fossil fuels will warm the planet.
1938
British engineer Guy Callendar determines that global temperatures are rising in line with increasing CO2 levels, and hypothesis that the two are linked.
1958
American scientist Charles David Keeling starts measuring CO2 levels over Hawaii’s Mauna Loa Observatory, resulting in the “Keeling Curve” graph that shows CO2 concentrations rising.
1990
At the UN’s Second World Climate Conference, scientists highlight the risks of global warming to nature and society. British Prime Minister Margaret Thatcher calls for binding emissions targets.
1992
Countries at the Rio Earth Summit sign the UN Framework Convention on Climate Change (UNFCCC). The treaty establishes the idea of “common but differentiated responsibilities,” meaning developed countries must do more to tackle climate-warming emissions because they emitted the most historically.
1995
UNFCCC signatories hold the first “conference of parties,” or COP, in Berlin, with the final document calling for legally binding emissions targets.
1997
At COP3 in Kyoto, Japan, parties agree to varied emissions cuts for each of the developed countries. In the United States, Senate Republicans denounce the Kyoto Protocol as “dead on arrival”.
2000
After losing the US presidential election, Al Gore begins giving talks worldwide on climate science and policy that eventually are made into the 2006 documentary An Inconvenient Truth. The film wins an Academy Award, while Gore and the UN climate science authority — the Intergovernmental Panel on Climate Change — receive the Nobel Peace Prize.
2001
US President George W. Bush calls the Kyoto Protocol “fatally flawed,” signaling the country’s effective exit.
2005
The Kyoto Protocol goes into effect after Russia ratifies it, meeting a requirement for ratification by at least 55 countries accounting for at least 55% of emissions.
2009
COP15 talks in Copenhagen nearly collapse after wrangling over a post-Kyoto framework, with countries voting to instead “take note” of a non-binding political statement.
2010
COP16 in Cancun fails to set new binding emissions targets, but the Cancun Agreements establishes a Green Climate Fund to help developing countries cut emissions and adapt to the conditions of a warmer world.
2011
COP17 talks in Durban, South Africa, falter after China, the United States and India refuse binding emissions cuts before 2015. Delegates instead extend the Kyoto Protocol through 2017.
2012
As Russia, Japan and New Zealand resist new emissions targets that do not extend to developing nations, countries at COP18 in Doha extend the Kyoto Protocol through 2020.
2013
Atmospheric CO2 levels cross 400 ppm for the first time in recorded history.
2015
The global average temperature rises beyond 1 degree Celsius over the preindustrial average. The COP21 talks result in The Paris Agreement, the first pact to call for increasingly ambitious emissions pledges from both developed and developing countries. Delegates also pledge to try to keep warming to within 1.5°C (2.7 degree Fahrenheit).
2017
US President Donald Trump pledges to remove the United States from the Paris treaty, which happens in 2020.
2018
Teen activist Greta Thunberg captures global attention while protesting outside Swedish parliament, and over time, rallies youths to join weekly climate protests worldwide.
2020
The annual COP is postponed amid the COVID-19 pandemic.
2021
Newly elected US President Joe Biden rejoins the Paris Agreement. Later at COP26, the Glasgow Pact sets a goal of using less coal and resolves some rules for trading carbon credits to offset emissions.
2022
The Intergovernmental Panel on Climate Change warns that the world is at risk of catastrophic and irreversible climate change. Later that year, COP27 in Sharm el-Sheikh, Egypt, agrees to form a Loss and Damage Fund for costly climate disasters, but does little to address the emissions fueling such disasters.
2023
At COP28 in the oil-producing United Arab Emirates, countries agree to transition away from fossil fuel use.
– Rappler.com