This Special Report by the IPCC responds to the request made under the Paris Agreement to assess what a 1.5°C increase in global temperatures means for our planet. It highlights how human activity has already warmed the Earth by approximately 1°C since pre-industrial times and projects that, if trends continue, global temperatures could reach 1.5°C between 2030 and 2052.
Warming has not been uniform. Land areas, especially the Arctic, are heating faster than oceans. This trend has led to more frequent and intense weather events like heat waves and heavy rainfall. Even if emissions stopped today, the effects of past emissions would persist for centuries, including rising sea levels. However, hitting 1.5°C won’t be inevitable if we reduce emissions aggressively and reach net-zero CO₂ in the coming decades.
The report stresses that the difference between 1.5°C and 2°C of warming is significant. At 1.5°C, the risks to ecosystems, human health, and livelihoods are lower. Still, even at this level, some irreversible impacts may occur, like the loss of specific ecosystems. To avoid the worst effects, countries must accelerate adaptation and mitigation strategies, including transforming energy systems, protecting vulnerable communities, and investing in sustainable development.
Projected Climate Change, Impacts, and Risks
Regional Climate Changes
Climate models show significant regional changes as temperatures rise from today’s levels to 1.5°C and from 1.5°C to 2°C. These include more extreme heat (especially in inhabited areas), heavier rainfall in some regions, and increased drought risk in others. Warming is expected to be stronger over land and in the Arctic. Hot days and heatwaves will intensify, especially in the tropics and mid-latitudes, and drought risks will increase, particularly at 2°C.
Sea Level Rise
Global sea levels are projected to rise less under 1.5°C than 2°C, with an estimated difference of 0.1 meters by 2100. This smaller rise could protect millions from flood risks. However, sea level rise will continue beyond 2100, driven by melting ice sheets, especially if warming exceeds 1.5°C. Low-lying coastal regions and islands will face more significant risks, but a slower rise at 1.5°C allows more time for adaptation.
Ecosystems on Land
Warming of 1.5°C will reduce the risk of biodiversity loss compared to 2°C. Fewer species are projected to lose large parts of their habitat, and ecosystem changes will be less severe. Tundra and boreal forests are vulnerable, but limiting warming can slow permafrost thaw. Protecting ecosystems helps preserve the services they provide to humans.
Ocean Impacts
Limiting warming to 1.5°C also reduces harm to marine life. Ocean warming, acidification, and oxygen loss would be less severe than at 2°C. Coral reefs are particularly threatened, with 70–90% loss at 1.5°C and over 99% at 2°C. Fishery productivity is expected to decline more at 2°C, especially in the tropics.
Human Systems and Well-being
Global warming increases health, food, water, and economic stability risks. Vulnerable populations – including those in drylands, small islands, and developing nations – face the most significant threats. Limiting warming to 1.5°C could reduce poverty risk and help avoid widespread losses in crop yields, water access, and public health.
Adaptation Needs
Fewer adaptation measures will be required at 1.5°C compared to 2°C. Many strategies exist, including ecosystem-based solutions, coastal protection, sustainable farming, and improved infrastructure. However, some limits to adaptation remain, especially for vulnerable communities and ecosystems. Challenges grow as warming increases, and adaptation must be local and inclusive.
Emission Pathways and System Transitions for 1.5°C
To limit global warming to 1.5°C with little or no overshoot, global CO₂ emissions must fall by roughly 45% from 2010 levels by 2030 and reach net zero around 2050. Staying below 2°C requires a 25% cut by 2030 and net zero around 2070. Non-CO₂ emissions like methane and black carbon must also decline significantly in both pathways. (high confidence)
Different strategies can meet the 1.5°C target by balancing reductions in energy demand, speed of decarbonization, and use of carbon removal. Each comes with unique trade-offs and challenges for sustainable development. (high confidence)
All 1.5°C-consistent scenarios require steep cuts in non-CO₂ pollutants, delivering co-benefits like improved air quality and health. However, increased reliance on bioenergy in some scenarios could raise nitrous oxide emissions, highlighting the need for proper management. (high confidence)
Staying within the carbon budget is critical. By 2017, an estimated 2200 GtCO₂ had already been emitted since pre-industrial times, leaving a remaining budget of around 420–580 GtCO₂ (for a 66%–50% chance of staying below 1.5°C). This budget is shrinking fast due to ongoing emissions and could be further reduced by permafrost thaw and other feedback. (high to medium confidence)
Solar radiation modification (SRM) is not included in assessed pathways. While it could theoretically reduce warming, it poses significant uncertainties and risks and does not address ocean acidification. (medium confidence)
Reaching the 1.5°C goal requires profound and rapid changes in energy, land use, infrastructure, cities, and industry. These transitions are unprecedented in scale and will need significant investment and policy support. (high confidence)
Changes must happen faster than in 2°C scenarios. Renewables are expected to supply 70–85% of electricity by 2050 in 1.5°C pathways, with coal use nearing zero. Technologies like CCS and energy storage will also play a role, especially in countries with favorable conditions. (high confidence)
Industry emissions would need to fall by 65–90% by 2050. It can be achieved through technologies like electrification, hydrogen, bio-based materials, and carbon capture – though economic and institutional factors may constrain large-scale deployment. (high confidence)
Urban and infrastructure systems must undergo significant shifts. It includes better planning, energy-efficient buildings, and cleaner transport. Barriers such as funding and local capacity may limit progress. (medium to high confidence)
Land-use changes are also key. Scenarios suggest a shift in land from food and pasture to forests and bioenergy, but such transitions must balance food security, biodiversity, and carbon storage needs. Policy, finance, and governance will be critical. (high confidence)
Meeting the 1.5°C goal will require significant investment – around $830 billion per year more than current policies – mainly in low-carbon energy and efficiency. Total energy-related investments could rise by 12% compared to 2°C pathways. (medium confidence)
Abatement costs are expected to be 3–4 times higher than 2°C pathways. However, the full economic costs and benefits of mitigation at 1.5°C are not yet fully understood due to limited data. (high confidence)
Carbon dioxide removal (CDR) methods will be needed to offset residual emissions and help reach net-negative emissions. Approaches include afforestation, soil carbon storage, BECCS, and direct air capture. CDR carries sustainability and feasibility limits, especially at large scales. (high confidence)
Strengthening the Global Response in the Context of Sustainable Development and Poverty Eradication
Current climate pledges under the Paris Agreement are projected to result in 2030 emissions of 52–58 GtCO₂eq/year – too high to keep global warming within 1.5°C. Even with ambitious action post-2030, such pathways will unlikely succeed unless emissions fall before 2030. Delayed action increases the risk of overshoot, dependence on large-scale carbon removal, and higher costs while reducing future flexibility and fairness. Early emissions cuts ease these challenges.
Limiting warming to 1.5°C brings more significant benefits for sustainable development, poverty reduction, and equity than 2°C. Climate responses must align with the UN Sustainable Development Goals (SDGs), addressing social well-being, economic growth, and environmental protection. Ethical and equitable approaches are essential to reducing unequal burdens on vulnerable populations.
Enabling climate action requires stronger institutions, finance, governance, innovation, and behavioral change. If well-designed, adaptation strategies can support sustainable development by improving health, food and water security, disaster resilience, and ecosystem services. Poorly planned actions, however, risk unintended harms, such as rising emissions, inequality, or ecosystem degradation.
Integrated approaches combining mitigation and adaptation can accelerate transitions in rural and urban areas. Some actions offer mutual benefits – like low-carbon buildings that reduce cooling needs – while others, such as large-scale bioenergy, may conflict with food security or land use priorities if not carefully managed.
Climate action aligned with the SDGs offers more synergies than trade-offs, particularly in health, clean energy, and sustainable cities. Low-demand pathways that reduce energy use, material consumption, and meat intake align significantly with development goals and the least dependence on carbon removal.
However, large-scale land-based mitigation (e.g., afforestation, BECCS) can compete with food production, affecting food security and biodiversity. Proper design and local context are essential to minimize these risks. Fossil fuel-dependent regions may face economic disruption, requiring policies for diversification and just transitions.
Redirecting a small share of mitigation funding toward social protections can reduce negative impacts on energy access, poverty, and food security. Finance, innovation, and education are crucial to drive systemic change. Supportive policies and governance can unlock private investment and enhance equity, resilience, and cooperation.
Sustainable development is a foundation for profound societal changes to limit warming. Climate-resilient development pathways require more decisive action from all levels of society. Social justice, equity, and international cooperation ensure inclusive, fair transitions, especially for vulnerable countries and communities.
Core Concepts
Global Mean Surface Temperature (GMST): The average land and ocean surface temperatures across the globe. It reflects temperature changes compared to a set reference period.
Pre-industrial: The time before large-scale industrial activity began, roughly before 1750. For measurement, the years 1850-1900 are often used to represent this baseline.
Global Warming: The long-term increase in GMST typically averaged over 30 years, compared to pre-industrial levels.
Net Zero CO2 Emissions: When human-caused CO2 emissions are balanced by CO2 removal from the atmosphere over a specific time.
Carbon Dioxide Removal (CDR): Human efforts to take CO2 from the air and store it in land, oceans, geological formations, or products. This excludes natural processes that are not driven by human activity.
Total Carbon Budget: The total amount of CO2 humanity can emit from pre-industrial times to reaching net zero while still limiting warming to a certain level.
Remaining Carbon Budget: The amount of CO2 that can still be emitted and stay within a temperature goal.
Temperature Overshoot: A temporary rise above a specific global temperature target before potentially dropping back down.
Emission Pathways: Projected future trends of global emissions. These are classified by how they align with temperature limits like 1.5°C.
Impacts: The consequences of climate change on people, ecosystems, economies, and infrastructure. These can be positive or negative.
Risk: The potential for harm from climate hazards is influenced by the hazard itself and how vulnerable or exposed people and systems are.
Climate-Resilient Development Pathways (CRDPs): Development routes that aim to reduce poverty and inequality while strengthening resilience to climate impacts and cutting emissions.
Acknowledgments
This report was made possible through the dedicated work of authors, reviewers, chapter scientists, technical support teams, and contributing institutions. Special thanks go to the IPCC Vice-Chairs, who have hosted organizations worldwide and supported governments and universities. Their efforts ensured the preparation, review, and communication of this Special Report on Global Warming of 1.5°C.
The IPCC Secretariat, technical support units, figure designers, editors, and the team behind the official website all played critical roles in bringing this report to life. Their collaboration and expertise enabled a thorough and accessible summary for policymakers and the public.
Mary Watson
