1 / 22Late 1800s | For millennia before the industrial revolution, atmospheric CO2 levels remained steady at around 280 parts per million (ppm). In the 1890s, Swedish scientist Svante Arrhenius first calculates the potential temperature rise caused by doubling CO2 levels, laying the groundwork for understanding human impact on the climate.
2 / 221938 | British engineer Guy Callendar links rising global temperatures to increasing CO2 emissions, a breakthrough that forms the basis for modern climate science.
3 / 221958 | US scientist Charles David Keeling begins measuring CO2 levels at Hawaii’s Mauna Loa Observatory, producing the now-famous “Keeling Curve” that shows the rise in carbon concentrations over time.
4 / 221990 | At the UN’s Second World Climate Conference, scientists warn of the dangers of global warming, prompting UK Prime Minister Margaret Thatcher to call for binding emissions targets.
5 / 221992 | At the Rio Earth Summit, the UN Framework Convention on Climate Change (UNFCCC) is signed by over 150 countries, establishing the principle of “common but differentiated responsibilities,” which asserts that developed nations should take more responsibility for addressing climate change due to their historical emissions.
6 / 221995 | The first official “Conference of the Parties” (COP) is held in Berlin, where a document is agreed upon calling for legally binding emissions reductions.
7 / 221997 | At COP3 in Kyoto, Japan, the Kyoto Protocol is adopted, mandating specific emissions reductions for developed countries. The US Senate, however, rejects the treaty, calling it “dead on arrival.”
8 / 222000 | After losing the US presidency, Al Gore begins a global climate campaign, culminating in the release of his documentary An Inconvenient Truth in 2006. The film wins an Academy Award, and Gore shares the Nobel Peace Prize with the UN Intergovernmental Panel on Climate Change (IPCC).
9 / 222001 | US President George W. Bush announces that the US will not ratify the Kyoto Protocol, effectively withdrawing the country from the international climate agreement.
10 / 222005 | The Kyoto Protocol officially comes into force after Russia ratifies it, fulfilling the requirement for 55 countries accounting for 55% of global emissions to join.
11 / 222009 | COP15 in Copenhagen nearly collapses as nations fail to agree on a post-Kyoto framework, resulting in a non-binding political agreement.
12 / 222010 | At COP16 in Cancun, the Green Climate Fund is established to assist developing nations in cutting emissions and adapting to climate change, though no binding emissions reductions are set.
13 / 222011 | COP17 in Durban sees progress as countries agree to extend the Kyoto Protocol through 2017, but major emitters like the US, China, and India refuse to commit to binding cuts before 2015.
14 / 222012 | COP18 in Doha extends the Kyoto Protocol through 2020, but resistance from key countries, including Russia and Japan, highlights ongoing tensions around equity and responsibility in addressing emissions.
15 / 222013 | CO2 levels surpass 400 ppm for the first time in recorded history, signaling an alarming increase in greenhouse gases in the atmosphere.
16 / 222015 | At COP21 in Paris, the landmark Paris Agreement is adopted, aiming to limit global warming to well below 2°C and to pursue efforts to limit it to 1.5°C. This marks the first universal climate pact, with all countries, both developed and developing, pledging to reduce emissions.
17 / 222017 | US President Donald Trump announces plans to withdraw from the Paris Agreement, a move that officially takes effect in 2020.
18 / 222019Climate activist Greta Thunberg told the US Congress, “I know you are trying but just not hard enough. Sorry” during her visit to the US Senate. (Image: Shutterstock)
19 / 222020 | The COVID-19 pandemic forces the postponement of the annual COP gathering, putting climate negotiations on hold for the year.
20 / 222021 | Newly elected US President Joe Biden reenters the Paris Agreement, signaling a renewed US commitment to global climate efforts. At COP26 in Glasgow, the Glasgow Pact sets ambitious goals for reducing coal use and resolving carbon trading issues.
21 / 222022 | The IPCC releases a dire warning that the world is at risk of catastrophic, irreversible climate change. At COP27 in Sharm el-Sheikh, Egypt, a Loss and Damage Fund is established to compensate vulnerable nations for the impacts of climate disasters, but little progress is made on reducing emissions.
22 / 222023 | At COP28 in the United Arab Emirates, oil-producing nations take center stage as the conference commits to transitioning away from fossil fuels.
