The 1.5-degree target is a climate goal that aims to keep the rise in human-caused global temperatures, due to greenhouse gases, below 1.5°C. This goal is measured as an average over 20 years, starting from the beginning of industrialization and ending in the year 2100. Scientists use the average temperature from the years 1850 to 1900 as the pre-industrial temperature for comparison.

Background

In 2015, during the 21st United Nations Climate Change Conference (COP 21), nearly all countries in the world signed the Paris Agreement. This agreement states that countries aim to take actions to help limit global temperature increases to 1.5 degrees Celsius. A report from the Intergovernmental Panel on Climate Change (IPCC) explains that keeping warming below 1.5 degrees Celsius would have better results than limiting it to 2 degrees Celsius. However, the IPCC also says that efforts to reduce greenhouse gas emissions before 2023 are not enough. If action is not taken quickly, global temperatures could rise by about 3.2 degrees Celsius over the next 70 years, leading to serious problems for people and the environment.

The World Meteorological Organization (WMO) predicted that the 1.5-degree temperature threshold would be crossed in at least one year between 2023 and 2027. In fact, 2024 was the first full year in which global temperatures were above 1.5 degrees Celsius compared to pre-industrial times. A study published in 2025 found that this event likely means Earth has already entered a 20-year period in which the average temperature increase will reach 1.5 degrees Celsius, as set by the Paris Agreement. According to the United Nations Environment Programme (UNEP), if all current climate protection plans are fully carried out without delays, the world could still face dangerous warming of up to 2.9 degrees Celsius.

Achievability

In a 2017 study, the chance of meeting the 1.5-degree target was considered low. At that time, scientists believed that even without adding more greenhouse gases to the atmosphere, the average global temperature would rise by at least 1.1°C compared to pre-industrial times. There was a 13% chance that temperatures could reach 1.5°C or higher. Another study from the same year suggested it was unlikely that global warming would stay below 2°C by 2100, let alone 1.5°C. Models used at the time, which included predictions about economic growth and population changes, estimated only a 1% chance of meeting the 1.5°C target.

However, the IPCC’s 2018 special report on 1.5°C global warming stated that the target could still be achieved. To do this, human CO₂ emissions would need to drop significantly before 2030 and reach net zero by around 2050. This would require reducing reliance on fossil fuels and using more renewable energy, as well as eating more plant-based foods. Scientists also estimated that up to 100 to 1,000 billion tons of CO₂ would need to be removed from the atmosphere by the end of the century. This is equal to 2.5 to 25 times the yearly CO₂ emissions of about 40 gigatons. One way to remove CO₂ naturally is through actions like planting trees and restoring wetlands, but these methods alone may not be enough. Scientists also suggested using technology to capture and store CO₂ if global temperatures exceed 1.5°C. However, it is not certain whether these methods would work on a large scale.

A 2023 study said the 1.5°C target would likely fail between 2033 and 2035, even in the best-case scenarios. Another report from the same year stated that meeting the 1.5°C goal and reducing emissions to zero by 2050 was "not plausible."

A 2023 case study on London found that reducing private car use in major cities could be the biggest step toward meeting the 1.5°C target. Scientists suggested measures such as community car-sharing, redesigning streets using a "superblock" model, creating compact cities with local services, stopping large road projects, and using dynamic tolls on busy or dangerous roads.

Global plans to produce coal, oil, and gas continue to exceed the levels needed to limit climate change. Since economic growth is closely linked to CO₂ emissions, reducing the pace of economic growth may be necessary to meet the 1.5°C and 2°C targets. Research by Jason Hickel, for example, shows that growth goals set by the International Monetary Fund (IMF) may conflict with these climate targets.

Recent studies suggest that achieving the 1.5°C target by removing CO₂ from the atmosphere after it has already been released (called an "overshoot scenario") may have been overestimated due to long-term, irreversible effects. A 2024 survey by The Guardian found that only 5% of climate scientists believed the 1.5°C target was achievable at the start of the year.

Advantages compared to the 2-degree target

A report from the Intergovernmental Panel on Climate Change (IPCC) compares the effects of global warming at 1.5°C to those at 2°C. Key findings include:

• At 1.5°C, average temperatures, heat waves, droughts, heavy rain, and areas with less rain would increase less than at 2°C.
• Sea levels would rise 0.1 meter less by keeping warming at 1.5°C instead of 2°C. Based on 2010 population data and without adaptation efforts, 10 million fewer people would be affected by rising seas at 1.5°C compared to 2°C. Sea levels would still rise at 1.5°C, but more slowly than at 2°C.
• Fewer species would go extinct, and ecosystems on land, in fresh water, and along coasts would face less damage. This would help preserve ecosystem services for longer.
• Oceans would warm and become more acidic less severely at 1.5°C. Oxygen levels in oceans would drop less, and biodiversity and fish catches would decline less. A summer without Arctic sea ice would happen once every 100 years instead of once every 10 years.
• Risks to human health, safety, livelihoods, food and water supplies, and economic growth would be lower at 1.5°C than at 2°C.
• Fewer changes to life and environments would be needed at 1.5°C. Some systems, both human and natural, would reach their limits of adaptation at 1.5°C, but the harm caused by exceeding these limits would be smaller than at 2°C.

The risk of triggering dangerous tipping points in Earth’s climate system, which could lead to uncontrollable changes, is much lower at 1.5°C. For example, melting of the Greenland ice sheet or Arctic sea ice might occur with warming between 1.5°C and 2°C. The tipping point for the West Antarctic ice sheet may already have been reached, but 1.5°C warming would slow its melting by ten times compared to 2°C. However, the carbon budget of 500 billion tons, which gives a 50% chance of keeping warming below 1.5°C, may already be nearly used up.

Compared to current IPCC projections, meeting the 1.5°C target could reduce climate-related migration by 80%, as fewer areas would become uninhabitable. According to CAN Europe, aligning Europe with the 1.5°C goal could save 1 trillion euros by 2030.

Assessment in the climate protection movement

Because the IPCC and climate scientists are unsure if the 1.5-degree target can be reached, groups like Scientist Rebellion say the goal should be considered too difficult to achieve politically. Groups such as Climate Restart, which started the 2023 Berlin climate neutrality referendum, argue that reducing carbon emissions in developed countries must still follow the 1.5-degree target to reduce risks. Scientists Wim Carton and Andreas Malm from Lund University criticize climate scientists for using models that assume the 1.5-degree target is achievable for too long, even though these models rely on unlikely ideas that have not focused enough on real-world situations.

Use as a slogan

The phrases "1.5 degrees" or "1.5°C" are frequently used as messages by activist groups, such as Fridays for Future, since July 2022. For example, the message "We all for 1.5°C" was written on the road in Hamburg's Mönckebergstraße. Additionally, during the protest at Lützerath that began in 2022, people used the message "1.5°C means: Lützerath stays!"