SR1.5

SR1.5 is the shorthand name for the Intergovernmental Panel on Climate Change (IPCC) Special Report on Global Warming of 1.5°C, approved in Incheon, Republic of Korea, in October 2018. It was prepared in response to an invitation in the decision adopting the Paris Agreement (Decision 1/CP.21, December 2015), which asked the IPCC to assess the impacts of 1.5°C warming and related emissions pathways.

The report concluded that human activities had already caused roughly 1.0°C of warming above pre-industrial levels and that, on current trajectories, warming would likely reach 1.5°C between 2030 and 2052. It found that limiting warming to 1.5°C rather than 2°C would meaningfully reduce risks to ecosystems, food security, water supply, and human health—for example, smaller losses of coral reefs, less sea-level rise, and fewer people exposed to heat extremes.

Crucially, SR1.5 quantified the mitigation effort required: global net anthropogenic CO₂ emissions would need to fall by about 45% from 2010 levels by 2030 and reach net zero around 2050 to give a reasonable chance of holding warming to 1.5°C with limited or no overshoot. All assessed 1.5°C pathways rely on some degree of carbon dioxide removal (CDR).

Politically, SR1.5 reframed climate diplomacy. The "1.5°C" figure—previously a Paris aspirational ceiling alongside the 2°C target—became the de facto benchmark cited by the UN Secretary-General, the High Ambition Coalition, AOSIS, and youth movements. At COP24 in Katowice (2018), a dispute over whether parties would "welcome" or merely "note" the report exposed divisions between climate-vulnerable states and major fossil-fuel producers including the US, Saudi Arabia, Russia, and Kuwait.

SR1.5 was followed by SROCC (oceans and cryosphere) and SRCCL (land), and its findings were largely reaffirmed and updated in the IPCC's Sixth Assessment Report (AR6, 2021–2023).