Human-Induced and Observed Global Warming, and Trajectory

Temperature Indicators

Global warming is defined as the change in average surface temperature over a long period. To have a clear picture of human impact and natural variability, the following indicators are defined as:

• Observed Warming: Annual, over a single year. Decadal, over ten years.
• Human-Induced Warming: Annual, over a single year. Decadal, over ten years.

Observed Warming

The Annual Observed Warming is directly related to the impacts of climate-related events in a given year; it is therefore useful for planning climate adaptation. However, this value fluctuates quite a lot each year due to natural processes such as solar variation, volcanic eruptions, and El Niño oscillations.

The Decadal Observed Warming removes these annual fluctuations and highlights the long-term trend of global average surface temperature increase.

Human-Induced Warming

The Annual Human-Induced Warming highlights the long-term trend of global warming by ignoring natural variability, removing the “noise” of the naturally caused fluctuations from the “signal” of human activities. Annual Human-Induced Warming also shows a more recent value compared to decadal averages. This makes Annual Human-Induced Warming the best indicator to track humanity’s progress against the Paris Agreement goal of limiting the global temperature increase to well below 2 °C (3.6 °F), while pursuing efforts to limit the increase to 1.5 °C (2.7 °F).

The direct comparison of Decadal Human-Induced Warming values with the long-term trend of Decadal Observed Warming demonstrates that essentially all the global warming was human-induced.

Human contributions to warming come from well-mixed greenhouse gases consisting of CO2, CH4, N2O, and F-gases, and other human forcings like aerosol radiation interaction, aerosol-cloud interaction, black carbon on snow, contrails, ozone, stratospheric H2O, and land use. Human-induced warming is directly related to human activities and changes predictably and smoothly each year.

Rate of Warming per Decade

Human-caused warming has increased at a rate of around 0.27°C per decade (2015-2024) and is mainly, roughly 80%, due to the continued build-up of greenhouse gases in the atmosphere, but also due to declines in planet-cooling aerosols that have been masking some of the warming we would have otherwise experienced.

Years Expected to Breach Paris Agreement Limits

The Paris Agreement, a legally binding international treaty on climate change, sets an overarching goal to hold “the increase in the global average temperature to well below 2°C above pre-industrial levels” and pursue efforts “to limit the temperature increase to 1.5°C above pre-industrial levels.” To limit global warming to 1.5°C, greenhouse gas emissions must peak before 2025 at the latest and decline by 43% by 2030.

Based on the current Human-Induced Warming and the rate of warming:

• The estimated year of breaching the 1.5 °C (2.7 °F) limit is 2030.
• The estimated year of breaching the 2 °C (3.6 °F) limit is 2048.

Key Take-Aways

• Likely, the world has now seen the global average temperature exceed 1.5°C above its pre-industrial level [1.39-1.65°C] for one year, although human-caused warming remains below this — best estimate up to 2024: 1.36°C.
• The difference can be explained by El Niño and warmer-than-average North Atlantic waters.
• This is unprecedented in at least the last 2,000 years, but not surprising. Given the level of human-induced warming, we might currently expect to see temperatures above 1.5°C on average one year in six years. However, 2024 followed an El Niño year, and the North Atlantic waters were warmer than average, so the likelihood of such a scenario increases to once every two years, highlighting the role that natural variability can play in shaping global annual temperatures.
• 2024 should not be seen as an exception — this is the harsh reality we must now expect, as new global temperature records will continue to be set until emissions from fossil fuels and deforestation reach net zero.
• For the most recent decade (2015-2024), the temperature was 1.24°C higher than in pre-industrial times, of which 1.22°C was caused by human activities. Allowing for small uncertainties, this means that essentially all the global warming was human-induced.
• The most recent decade (2015-2024) was 0.31°C warmer than the previous decade (2005-2014). These changes, although amplified somewhat by the exceptionally warm years in 2023 and 2024, report a higher decadal rate.
• Human-caused warming has increased at a rate of around 0.27°C per decade (2015-2024) and is mainly (roughly 80%) due to the continued build-up of greenhouse gases in the atmosphere, but also due to declines in planet-cooling aerosols that have been masking some of the warming we would have otherwise experienced.
• The rapid warming over the last few decades has resulted in record extreme temperatures over land.
• Reaching 1.5°C global warming on a long-term basis is now inevitable in around five years if we don’t take the immediate, transformative action needed to reduce emissions from fossil fuels and deforestation to net zero.
• To achieve net zero and to stabilize temperatures, the pace and scale of climate action globally must match the rate and scale of the climate challenge.

About the Data

The data is produced by the Indicators of Global Climate Change (IGCC) initiative to spread indicators of climate change that are consistent with the IPCC Assessment Report 6. The IGCC produces estimates for key climate indicators: emissions of greenhouse gases and short-lived climate forcers, greenhouse gas concentrations, radiative forcing, surface temperature changes, the Earth’s energy imbalance, warming attributed to human activities, the remaining carbon budget, sea level rise, and estimates of global temperature extremes.

Units and Measures

Degrees Celsius (°C) or degrees Fahrenheit (°F). Numerical ranges of confidence are presented in square [ ] brackets.

Data Sources

IGCC Indicators of Global Climate Change 2024: annual update of key indicators of the state of the climate system and human influence, Piers M. Forster et al.
Credits: Smith, C., Walsh, T., Gillett, N., Hauser, M., Krummel, P., Lamb, W., Lamboll, R., Mühle, J., Palmer, M., Ribes, A., Schumacher, D., Seneviratne, S., Trewin, B., von Schuckmann, K., & Forster, P. (2025). Indicators of Global Climate Change 2024 (v2025.05.02). Zenodo.Update cycle: yearlyDelay: Up to a year