Early Warnings: Government Knowledge of Climate Change and Legal Responsibility for Climate Harm

The report argues that many high-emitting governments knew about the link between fossil fuel combustion and global warming as early as the 1960s, triggering legal duties to prevent harm long before the 1990s. It uses a timeline of scientific milestones and country-specific evidence to challenge claims by States that awareness only emerged in the late 1980s, linking this knowledge to the 'no-harm' principle of customary international law.

• The International Court of Justice (ICJ) issued a unanimous advisory opinion in July 2025 stating that all States have binding duties under customary international law to prevent, mitigate, and remedy climate harm, including reducing greenhouse gas emissions and the activities that cause them.
• Under the 'no-harm' or transboundary harm principle, a State's legal obligation to prevent climate change is triggered when it becomes aware of the causes of climate change and its foreseeable harms.
• Scientific evidence that carbon dioxide (CO2) from fossil fuels could warm the planet was established in the 19th century, with John Tyndall's 1861 research and Svante Arrhenius's 1896 estimate that doubling CO2 would raise global temperatures by five to six degrees Celsius.
• By the 1960s, a scientific consensus had emerged that the earth was warming due to human activity, and this information was communicated to government officials in high-emitting countries.
• The US government had internal knowledge of climate risks in the 1960s, including a 1965 report from President Lyndon B. Johnson’s Science Advisory Committee that warned of large temperature increases and catastrophic sea level rise by the year 2000.
• Other high-emitting States, including Germany, France, the United Kingdom, and Canada, had public discussions or government-level recognition of the 'carbon dioxide issue' by the 1970s.
• The fossil fuel industry's own research often confirmed or preceded government knowledge, with companies like Humble Oil (ExxonMobil) acknowledging the link between fossil fuels and rising CO2 as early as 1957.
• Claims by major emitters, such as the US and China, that general awareness of climate risks only developed in the late 1980s or 1979 are contradicted by evidence of earlier scientific warnings and government-funded research.
• Indigenous groups, particularly in the Arctic, reported changes to sea ice and temperature in the 1960s and 1970s, providing early warnings that were communicated to government bodies.

APA

Center for International Environmental Law (n.d.). Early Warnings: Government Knowledge of Climate Change and Legal Responsibility for Climate Harm. https://www.ciel.org/wp-content/uploads/2026/07/Government_Knowledge_Climate_Change_Legal_Responsibility_for_Climate_Harm.pdf

Chicago

Center for International Environmental Law. Early Warnings: Government Knowledge of Climate Change and Legal Responsibility for Climate Harm. n.d. https://www.ciel.org/wp-content/uploads/2026/07/Government_Knowledge_Climate_Change_Legal_Responsibility_for_Climate_Harm.pdf.

Wikipedia

{{cite report |author=Center for International Environmental Law |title=Early Warnings: Government Knowledge of Climate Change and Legal Responsibility for Climate Harm |url=https://www.ciel.org/wp-content/uploads/2026/07/Government_Knowledge_Climate_Change_Legal_Responsibility_for_Climate_Harm.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{centerforinternationalenvironmentallawndearly, author = {{Center for International Environmental Law}}, title = {{Early Warnings: Government Knowledge of Climate Change and Legal Responsibility for Climate Harm}}, institution = {Center for International Environmental Law}, url = {https://www.ciel.org/wp-content/uploads/2026/07/Government_Knowledge_Climate_Change_Legal_Responsibility_for_Climate_Harm.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }