1.5-degree target: Climate goal, feasibility and global implications

Overview

The 1.5-degree target represents a specific climate goal aimed at limiting the man-made global temperature increase caused by the greenhouse effect to 1.5 °C. This limit is calculated as a 20-year average, measured from the beginning of industrialization through to the year 2100. The target serves as a critical benchmark in global climate policy, distinguishing between moderate and severe climatic shifts. The baseline for this calculation is defined as the average value for the years 1850 to 1900, which is used as the pre-industrial reference point. This specific period provides a standardized metric for comparing current and future temperatures against historical norms.

The methodology relies on a 20-year moving average to smooth out short-term variability and natural fluctuations in global temperatures. By using this averaging method, the target accounts for year-to-year anomalies and provides a more stable indicator of long-term warming trends. The calculation spans from the onset of the industrial era to the end of the 21st century, offering a comprehensive view of cumulative warming. The pre-industrial baseline of 1850–1900 is widely accepted in climate science as the period before significant anthropogenic influence on the global climate system.

Paris Agreement Context

The 1.5-degree target was formally commissioned in 2015, coinciding with the adoption of the Paris Agreement. This international treaty established the framework for global climate action, with the 1.5 °C limit serving as a key objective for many signatory nations. The target reflects the collective ambition to mitigate the most severe impacts of climate change, including extreme weather events, sea-level rise, and biodiversity loss. By setting a specific numerical goal, the Paris Agreement provided a clear direction for national climate policies and international cooperation. The 1.5-degree target remains a central focus of ongoing climate negotiations and policy implementations worldwide.

Background

The 1.5-degree target was formally established as a global climate goal during the 2015 United Nations Climate Change Conference, known as COP 21. This landmark agreement set the objective of limiting the anthropogenic increase in global average temperature to 1.5 °C above pre-industrial levels. The pre-industrial baseline is scientifically defined as the average temperature recorded between the years 1850 and 1900. The target aims to mitigate the impacts of the greenhouse effect by calculating the temperature rise from the onset of industrialization through the year 2100. This specific threshold was chosen to reduce the risks and impacts of climate change compared to a 2 °C increase, influencing energy infrastructure planning and policy worldwide.

Recent Temperature Trends and Projections

Global warming has accelerated significantly in recent years, bringing the world closer to this critical threshold. The year 2024 marked a historic milestone as the first calendar year where the global average temperature exceeded the 1.5 °C limit relative to the pre-industrial baseline. This event highlighted the urgency of the target and the rapid pace of current warming trends. The World Meteorological Organization (WMO) has provided critical assessments regarding this trajectory. According to WMO predictions, the period from 2023 to 2027 is highly likely to see at least one year where the global temperature temporarily exceeds the 1.5 °C threshold. These projections underscore the volatility of the climate system and the increasing frequency of heat extremes.

Despite the immediate proximity to the 1.5 °C limit, long-term projections remain challenging. The United Nations Environment Programme (UNEP) has projected that current national climate policies and pledges could lead to a total global warming of approximately 2.9 °C by the end of the century. This significant gap between the 1.5 °C target and the 2.9 °C projection illustrates the disparity between political commitments and the actual implementation of mitigation strategies. Achieving the 1.5-degree target requires a substantial acceleration in the deployment of renewable energy, energy efficiency measures, and carbon capture technologies to align the 2.9 °C trajectory with the stricter 1.5 °C goal.

How feasible is the 1.5-degree target?

The feasibility of limiting global warming to 1.5 °C has been a subject of intense scientific scrutiny since the target's formalization in 2015. Early assessments cast significant doubt on its achievability. Studies conducted in 2017 indicated a low probability of success, suggesting only a 13% chance of reaching the 1.5 °C threshold without further emissions and merely a 1% probability in broader climate models. These figures highlighted the steep challenge of aligning global energy infrastructure and policy with such a narrow temperature band. However, the 2018 IPCC report offered a more structured pathway, stating that the target remains achievable if global net-zero emissions are reached by 2050. This assessment shifted the focus from mere probability to the necessity of rapid decarbonization across all sectors. The report emphasized that while difficult, the 1.5 °C goal was not yet out of reach, provided that immediate and sustained action was taken. Despite these findings, recent prognoses have grown increasingly pessimistic. A 2023 analysis suggested a potential collapse of the 1.5 °C target between 2033 and 2035, driven by delayed policy implementation and rising greenhouse gas concentrations. This timeline underscores the urgency of current energy transitions. Public and scientific sentiment reflects this growing concern. A survey by The Guardian revealed that only 5% of scientists expect the 1.5 °C target to be achieved, indicating a widespread skepticism about the current trajectory of global climate efforts. These varying perspectives highlight the complex interplay between scientific modeling, policy action, and real-world emissions data.

What are the required mitigation strategies?

Required Mitigation Strategies

Achieving the 1.5 °C target requires a comprehensive transformation of global energy systems, land use, and consumption patterns. The core strategy involves a rapid shift from fossil fuels to renewable energy sources to drastically reduce greenhouse gas emissions. This transition must be complemented by significant changes in human behavior, including the adoption of plant-based diets to lower the carbon footprint of the food system.

Carbon Dioxide Removal

Limiting warming to 1.5 °C necessitates substantial carbon dioxide removal (CDR) from the atmosphere. Estimates indicate that between 100 and 1000 billion tons of CO2 must be removed. This volume represents 2.5 to 25 times the current yearly emissions of 40 gigatons. Such large-scale removal is critical to offset residual emissions and potentially reverse some warming if the target is temporarily exceeded.

Key Sectors and Technologies

The Agriculture, Forestry, and Other Land Use (AFOLU) sector plays a vital role in these mitigation efforts. Strategies include enhancing carbon sinks through reforestation and sustainable land management. Additionally, carbon capture and storage (CCS) technologies are essential for capturing emissions from industrial processes and power generation, storing them underground to prevent atmospheric release.

Case Studies: Urban Transport

Urban areas are critical fronts for emission reductions. The London case study highlights the potential of private transport reduction. By decreasing reliance on private vehicles through improved public transit, cycling infrastructure, and pedestrian zones, cities can significantly cut local emissions. This approach demonstrates how targeted urban policies contribute to the broader 1.5 °C goal.

Mitigation Strategy	Key Actions	Impact Area
Fossil Fuel Shift	Transition to renewables	Energy Sector
Carbon Removal	100–1000 billion tons CO2	Atmosphere
AFOLU	Land use optimization	Land Sector
Urban Transport	Reduce private vehicles	City Emissions

Why does the 1.5-degree limit matter?

The 1.5-degree target represents a critical threshold in climate science, defining the goal of limiting global temperature rise to 1.5 °C above pre-industrial levels. This limit is calculated using the average temperature from 1850 to 1900 as the baseline, extending to the year 2100. The significance of this specific limit lies in the disproportionate benefits it offers compared to a 2-degree scenario. While both targets require substantial mitigation, the difference between 1.5 °C and 2 °C translates into tangible reductions in extreme weather events, sea level rise, and biodiversity loss.

Comparative Climate Impacts

Limiting warming to 1.5 °C significantly reduces the frequency and intensity of heat waves and droughts. A key metric is sea level rise; achieving the 1.5-degree target results in a reduction of approximately 0.1 meters in global mean sea level compared to the 2-degree scenario. This difference is crucial for coastal communities and small island developing states. Additionally, the impact on the Arctic is profound. Under a 1.5 °C warming scenario, Arctic sea ice is expected to occur only once per century, whereas a 2-degree increase would see ice-free summers occur once per decade. This stability in the cryosphere helps mitigate feedback loops that accelerate global warming.

Human and Economic Benefits

The human cost of exceeding the 1.5-degree limit is substantial. Climate-induced migration is projected to be 80 percent lower if the 1.5 °C target is met compared to a 2-degree pathway. This reduction alleviates pressure on infrastructure and social services in receiving regions. Health outcomes also improve, with fewer heat-related mortality cases and reduced spread of vector-borne diseases. Economically, the benefits are quantifiable. For Europe, adhering to the 1.5-degree target could result in economic savings of one trillion euros by 2030. These savings stem from reduced adaptation costs, lower health expenditures, and enhanced productivity in key sectors.

Tipping Points and Stability

Achieving the 1.5-degree limit is essential for avoiding irreversible climate tipping points. These include the collapse of major ice sheets, the dieback of the Amazon rainforest, and the disruption of ocean circulation patterns. Maintaining global temperatures within this range preserves the stability of the cryosphere and reduces the risk of cascading effects that could lock in further warming. The target thus serves as a safeguard for both ecological integrity and human livelihoods, providing a clearer path to sustainable development.

How is the target viewed by the climate movement?

The 1.5-degree target faces divergent assessments from the climate movement, ranging from strategic necessity to political skepticism. Activists and scientists evaluate the goal through different lenses, balancing scientific urgency against implementation realities.

Scientific and Activist Perspectives

Scientist Rebellion argues that the target is politically unfeasible given current global trajectories. The group suggests that the gap between policy commitments and actual emissions reductions renders the 1.5 °C limit increasingly difficult to achieve without radical intervention. This view highlights the tension between the scientific definition of the target and the political will required to meet it.

In contrast, Climate Restart emphasizes decarbonization as the primary pathway to achieving the goal. This perspective focuses on the technical and economic mechanisms needed to reduce global emissions, viewing the 1.5-degree target as a viable objective if sufficient decarbonization efforts are deployed. The emphasis is on actionable strategies rather than political critique.

Critiques of Climate Science Assumptions

Wim Carton and Andreas Malm offer a more fundamental criticism, questioning the implausible assumptions underlying climate science simulations. They argue that the models used to project the 1.5-degree target rely on simplifications that may not accurately reflect complex socio-economic and environmental dynamics. This critique challenges the robustness of the scientific basis for the target, suggesting that the projections may be overly optimistic or dependent on uncertain variables.

These differing views reflect the broader debate within the climate movement about the feasibility and methodology of the 1.5-degree target. While some groups focus on political and strategic challenges, others scrutinize the scientific models that underpin the goal. The discussion underscores the complexity of defining and achieving a global climate target in a rapidly changing world.

The 1.5-degree target as a political slogan

The 1.5-degree target has evolved from a scientific metric into a potent political slogan and mobilizing framework for global climate activism. While the concept was formally commissioned in 2015 as part of the Paris Agreement, its adoption by grassroots movements has transformed it into a tangible benchmark for political accountability. Activist groups have increasingly leveraged the specific temperature threshold to articulate demands for immediate decarbonization and land-use reform, framing the 1.5 °C limit not merely as a climatological goal but as a deadline for political action.

Fridays for Future and Global Mobilization

Since July 2022, the Fridays for Future movement has strategically centered its messaging around the 1.5-degree target. This shift marked a consolidation of the movement's demands, moving from general awareness to specific policy enforcement. The slogan serves to unify disparate local chapters under a single, quantifiable objective. By anchoring protests to the 1.5 °C threshold, activists create a clear narrative of urgency, arguing that current policy trajectories are insufficient to meet the goal. This period saw a significant increase in the visibility of the target in mainstream media coverage of climate strikes, reinforcing its status as the primary metric for evaluating government climate action.

Regional Campaigns: Hamburg and Lützerath

Local campaigns have effectively localized the global target to drive specific political outcomes. In Hamburg, activists utilized the slogan 'We all for 1.5°C' to rally public support for municipal climate policies. This phrasing emphasizes collective responsibility and broad-based participation, linking individual action to the broader scientific target. Similarly, during the occupation of Lützerath, protesters adopted the slogan '1.5°C means: Lützerath stays!' This direct linkage between the temperature target and land preservation highlighted the conflict between fossil fuel extraction and climate goals. The Lützerath campaign demonstrated how the 1.5-degree target can be used to challenge specific infrastructure projects, arguing that preserving the area is necessary to remain within the 1.5 °C limit. These examples illustrate the versatility of the target as a political tool, capable of driving both broad electoral pressure and specific site-based protests.