Indicators of human-induced global warming, greenhouse gas emissions, and the remaining global carbon budget. Relevant to the Paris Agreement, IPCC AR6 consistent.

Indicators of Global Climate Change 2023

Indicators of Global Climate Change 2023, IGCC Initiative

First and foremost, this is the indicator that should be used to track our 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).

UNFCCC: Key aspects of the Paris Agreement

What is the difference between observed and human-induced warming?

Observed warming is the measured temperature of the planet, and 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; these yearly fluctuations mean that it can be difficult to see how close the current climate is to long-term average temperatures such as the 1.5 °C (2.7 °F) and 2 °C (3.6 °F) stabilization targets set out in the Paris Agreement.

Paper section 6: Global surface temperatures: Indicators of Global Climate Change 2023, Piers M. Forster et al.

Scientists, therefore, use techniques called “Detection and Attribution” to separate the “noise” of these naturally caused fluctuations from the “signal” of human-induced warming (sometimes also called anthropogenic warming). Human contributions to warming come from well-mixed greenhouse gases (consisting of CO2, CH4, N2O, and F-gases) and other human forcings (consisting of 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, making it useful for planning climate mitigation.

Paper section 7: Human-induced global warming: Indicators of Global Climate Change 2023, Piers M. Forster et al.

IPCC AR6: Chapter 3, Intergovernmental Panel on Climate Change Assessment Report 6

What is the difference between decade-average and single-year warming?

Two definitions were used to report recent levels of human-induced warming in the IPCC’s latest 6th Assessment Cycle: the decade-average and single-year values. The decade-average definition was used in the IPCC's 6th Assessment Report, and the single-year definition was used in its Special Report on Global Warming of 1.5 °C. The results for both definitions were updated in the Indicators of Global Climate Change 2023 paper using identical datasets and methods, which means that the two definitions are fully consistent with each other.

IPCC AR6: Intergovernmental Panel on Climate Change Assessment Report 6

Since climate change is defined as the change in average conditions (such as temperature) over a long period of time, the benefit of calculating human-induced warming by removing natural fluctuations is that it &quot;live&quot; tracks the signal of climate change over time, avoiding potential misconceptions resulting from short-term fluctuations due to natural processes that don’t contribute to the longer-term climate average.

Observed warming is therefore often reported using the decade-average value as a measure of how the overall climate has changed. Calculating the decade-average value of human-induced warming is, therefore, useful to compare how much of the observed long-term climate trend results from human activities. In 2023, the 2014-2023 averages for observed and human-induced warming were both at 1.19 °C (2.14 °F), demonstrating that almost all observed changes are a result of human activity.

While the single-year observed warming isn't as useful as an indicator of overall long-term climate change due to natural fluctuations each year, the human-induced warming level in a single year remains a good indicator of the level of climate change because these fluctuations have been filtered out. However, the single-year observed warming remains a useful indicator of expected climate impacts in a given year. In 2023, the observed and human-induced warming were 1.43 °C (2.57 °F) and 1.31 °C (2.36 °F), respectively, demonstrating the higher relative significance of natural fluctuations in a single year compared to the decade average.

Note that the decade-average warming is calculated for the most recent decade and the single-year warming is calculated for the most recent year; this results in a “lag” of around 5 years between them. For example, for the 2023 calculations, the 2014-2023 decade average is centered around 2018, whereas the 2023 single-year is centered on 2023.

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

The current human-induced warming of 1.19 °C (2.14 °F), with an uncertainty range from 1.0 (1.8 °F) to 1.4 °C (2.5 °F), is not far from the Paris Agreement's goal. It is clear that we are in a critical time period to mitigate climate change.

Climate Change Tracker is part of 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, and estimates of global temperature extremes.

This indicator was originally produced in IPCC AR6 (WG1 Chap. 3 Sect. 3.3.1.1.2). For the 2010-2019 period, human-induced warming averaged 1.07 [0.8 to 1.3] °C  (1.93 [1.4 to 2.3] °F). The IGCC re-evaluation for the same period resulted in the same numbers, and since then the warming has increased to 1.19[1.06 to 1.30] °C  (2.14[1.91 to 2.34] °F) for the currently most up-to-date period of 2014-2023.

Recent Human-Induced Warming

This is a simple estimate for when the 1.5 °C (2.7 °F) warming level, as mentioned by the Paris Agreement, will be reached based on the Current Human-Induced Warming and its recent changes. The Paris Agreement has the 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.

The estimated year, 2031, is the midpoint of the decade 2026 to 2035, in which we are projected to reach 1.5 °C (2.7 °F) warming.

It is a critical indicator because it highlights the time period that remains until 1.5 °C warming is reached by IPCC AR6 standards at the current trajectory. Reducing the impact of human activities on global warming will delay the estimated year.

Please note that on this trajectory, 1.5 °C warming will occur several years after the remaining carbon budget has been depleted; the calculation is formulated like this to consider future non-CO2 warming.

Temperature increase per decade in degrees Celsius (°C) or degrees Fahrenheit (°F), and the estimated year of reaching 1.5 °C (2.7 °F).

The rate of a 0.26 °C (0.47 °F) temperature increase per decade may seem small, but it is very significant. At this rate, 1.5 °C (2.7 °F) warming will be reached in the early-2030s. It is a critical decade in which to implement impactful mitigation efforts to adjust the trajectory.

Current Trajectory

Widget4_1Select

What are Human-Induced Global Warming and Observed Global Warming?

Human-induced and observed global warming are two related indicators of global warming for comparing the observed (actual) warming to the warming attributed to human activities.

Two definitions were used to report recent levels of human-induced warming in the IPCC&apos; latest 6th Assessment Cycle: the decade-average and single-year values. The decade-average definition was used in the IPCC's 6th Assessment Report, and the single-year definition was used in its Special Report on Global Warming of 1.5 °C. The results for both definitions were updated in the Indicators of Global Climate Change 2023 paper using identical datasets and methods, which means that the two definitions are fully consistent with each other.

Since climate change is defined as the change in average conditions (such as temperature) over a long period of time, the benefit of calculating human-induced warming by removing natural fluctuations is that it &quot;live&quot; tracks the signal of climate change over time, avoiding potential misconceptions resulting from short-term fluctuations due to natural processes that don&apos;t contribute to the longer-term climate average.

The chart emphasizes the difference between the steadily increasing human-induced temperature and the fluctuating increase in the observed warming. The constant fluctuations of increases and decreases in the observed temperature are very visible for the yearly values. Long-term climate change mitigation efforts should not be based on these yearly fluctuations, but should instead be based on the steady human-induced warming.

Despite the difference, both temperature indicators are linked and are continuing to increase without showing any signs of slowing down.

Full Article: Indicators of Global Climate Change 2023, Piers M. Forster et al.

In IPCC AR6 (WG1 Chap. 3 Sect. 3.3.1.1.2) for the 2010–2019 period, human-induced warming averaged 1.07 [0.8 to 1.3] °C (1.94 [1.4 to 2.3] °F). The newly repeated calculation for the same period resulted in the same numbers, and since then the warming has increased to 1.19[1.06 to 1.30] °C (2.14[1.91 to 2.34] °F) for the currently most up-to-date period of 2014-2023.

Regarding the observed warming in IPCC AR6 (Chap. 3 Sect. 3.3.1.1.2) for the 2010–2019 period, human-induced warming averaged 1.06 [0.88 to 1.21] °C (1.91 [1.58 to 2.18] °F). The newly repeated calculation for the same period resulted in 1.07 [0.89 to 1.22] °C (1.93 [1.60 to 2.20] °F), and since then the warming has increased to 1.19[1.06 to 1.30] °C (2.14[1.91 to 2.34] °F)  for the currently most up-to-date period of 2014-2023.

Comparison with the IPCC Special Report Global Warming of 1.5 °C

The IPCC Special Report 1.5 (Chap. 1 Sect. 1.2.1.3) originally reported the human-induced warming per year, and for 2017 it reported 1.0 [0.8 to 1.2] °C (1.8 [1.4 to 2.2] °F). Based on the new recalculation, it is now projected that in 2017 human-induced warming was 1.15 [0.9 to 1.4] °C (2.07 [1.6 to 2.5] °F) with values for 2023 having risen to 1.31 [1.1 to 1.7] °C (2.36 [2.0 to 3.1] °F).

Human-Induced and Observed Global Warming

What are the Yearly Human-Induced Greenhouse Gas Emissions in CO2 Equivalent?

These are the yearly greenhouse gas emissions that result from human activities. This includes the following emissions:

These emissions are the main drivers of human-induced warming. The CO2-equivalent unit makes it possible to compare the relative emissions from different gases. CO2-equivalents are calculated using the global warming potentials of the respective gases, in this case using a 100-year time horizon.

Paper section 2: Emissions: Indicators of Global Climate Change 2023, Piers M. Forster et al.

In the scientific literature, human-induced emissions are often referred to as anthropogenic emissions.

The sources are mostly fossil-fuel combustion emissions from coal, oil and gas, as well as emissions from industrial processes such as cement production.

CO2 land-use, land-use change and forestry

The main driver of these emissions is deforestation, which includes logging and forest degradation, as well as other land-use change activities. The emissions also take into account the absorption of CO2 by processes that remove CO2 from the atmosphere, such as afforestation and reforestation. It is the net effect that is indicated here.

Methane emissions by human activities such as rearing livestock, agricultural practices and fugitive fossil fuel emissions.

Common sources of Nitrous oxide are fossil fuel emissions and the agricultural use of synthetic fertilizer and manure.

Fluorinated gases are a group oF-gases defined by UNFCCC: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3). Fluorinated gases are also known as halogenated gases.

CO2-equivalent emissions are expressed in the total weight in gigatonnes per year.

Total emissions have risen almost continuously since the 1850s, and by staggering amounts in the last 100 years. Over the last 10 years, emissions have stabilized, but there is as yet no reduction in emissions, other than a temporary reduction in 2020 due to Covid.

CO2 emissions from fossil fuels and industry are by far the largest contributors to total emissions and have increased roughly ten-fold in the last 100 years. Emissions from methane, nitrous oxide and fluorinated gases have all grown significantly over the same period. The CO2 emissions from land-use, land-use change and forestry have been relatively steady for a very long time and have had a large historic impact.

The IPCC AR6 reported the average emissions per year for the 2010 to 2019 decade at 56±6 GtCO2e. A new reassessment of that same period, 2010 to 2019, resulted in slightly lower emissions of 53±5.5 GtCO2e, and the new assessment of the latest fully available period, 2013 till 2022, shows 53±5.4 GtCO2e.

The IGCC CO2 emissions data currently only contains Global Carbon Budget data since 1959. The historical data is taken directly from the Global Carbon Budget. The methane and nitrous oxide emissions data in IGCC is taken from PRIMAP. The F-gases value for 2023 is an estimate.

Yearly Human-Induced Greenhouse Gas Emissions in CO2 Equivalent

What is the Current Remaining Carbon Budget and Trajectory?

The Current Remaining Carbon Budget is the amount of CO2 expressed in Gigatonnes that can be emitted in the future to keep human-induced warming below limits such as 1.5 °C (2.7 °F), 1.7 °C (3.06 °F), 2 °C (3.6 °F).

The Remaining Carbon Budget is not just a single number. Scientists calculate budgets for a range of 'likelihoods' and limits. You can inspect the likelihood and the corresponding budget by adjusting the likelihood slider in the widget. A higher likelihood of limiting warming (67%, 83% or 90%) corresponds to a lower remaining carbon budget and a lower likelihood (10%, 17% or 33%) to a higher budget. 

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

United Nations: What is the Paris Agreement?

The number exhausted in is an estimate of the year when the remaining carbon budget will be exhausted based on a chosen likelihood and on the latest given exhaustion rate of 40 Gt CO2 per year.

The remaining carbon budget is only for CO2 emissions, and not to be confused with CO2-equivalent (CO2e) emissions. However, the budget calculations take into account that other human factors also influence the human-induced warming, for example methane CH4, N2O and sulfur dioxide. Unexpected changes in these factors also change the Remaining Carbon Budget, which is recalculated yearly by the IGCC.

The Remaining Carbon Budget is expressed in gigatonnes of CO2.

The current 2024 budget for a likelihood of 50% to stay under 1.5 °C (2.7 °F) is 200 gigatonnes CO2, with estimated exhaustion in 2029.

The current 2024 budget for a likelihood of 83% to stay under 1.5 °C (2.7 °F) is 100 gigatonnes CO2, with estimated exhaustion in 2026.

With current CO2 emissions (exhaustion rate), the budget will be exhausted within the next 12 years for all likelihoods. There could not be a clearer message that this decade is crucial for reducing carbon emissions.

More about remaining carbon budgets in the Indicators of Global Climate Change 2023 paper.

Paper section 8: Remaining carbon budget: Indicators of Global Climate Change 2023, Piers M. Forster et al.

The remaining carbon budget for the 50% likelihood of limiting warming to 1.5 °C (2.7 °F) was estimated in IPCC AR6 to be 500 Gt CO2 from the start of 2020. The updated assessment has reduced that budget to 200 Gt CO2 from the start of 2024. Various factors in the update caused the budget to be reduced by more than 160 Gt CO2 emissions in those 4 years.

IGCC Webiste: Indicators of Global Climate Change

Indicators of Global Climate Change 2023: Annual update of large-scale indicators of the state of the climate system and the human influence

Current Remaining Carbon Budget and Trajectory

What are the Yearly Total Human-Induced CO2 Emissions?

These are the total yearly CO2 emissions emitted through human activities. They are the sum of CO2 emissions from fossil fuels and industry plus emissions from land-use, land-use change and forestry. In the scientific literature human-induced emissions are often referred to as anthropogenic emissions.

Human-induced CO2 emissions are crucial because they are the largest driver of human-induced warming. Total CO2 emissions are also crucial in relation to the remaining carbon budget. The remaining carbon budget is based on CO2 emissions alone and should not be related to the sum of CO2-equivalent emissions from all gases.

This indicator is specifically about net emissions, which means that it also accounts for the fact that certain human activities absorb CO2 from the atmosphere, for example afforestation and reforestation.

CO2 emissions are expressed in the total weight in gigatonnes per year.

The long-term steady growth of yearly CO2 emissions since the 1950s has flattened in the last 10 years, but yearly emissions are not yet clearly reducing. A steady yearly reduction is necessary to not exhaust the remaining carbon budget during the long-term transition towards less carbon-dependent human activities.

Full paper: Indicators of Global Climate Change 2023: Annual update of large-scale indicators of the state of the climate system and the human influence

The IGCC CO2 emissions data currently only contains Global Carbon Budget data since 1959. The historic data is taken from the Global Carbon Budget directly.

Indicators of Global Climate Change 2023

Recent Human-Induced Warming

Current Trajectory

Human-Induced and Observed Global Warming

Yearly Human-Induced Greenhouse Gas Emissions in CO₂ Equivalent

Current Remaining Carbon Budget and Trajectory

Yearly Total Human-Induced Net CO₂ Emissions

Indicators of Global Climate Change 2023

Recent Human-Induced Warming

Current Trajectory

Human-Induced and Observed Global Warming

Yearly Human-Induced Greenhouse Gas Emissions in CO2 Equivalent

Current Remaining Carbon Budget and Trajectory

Yearly Total Human-Induced Net CO2 Emissions

Yearly Human-Induced Greenhouse Gas Emissions in CO₂ Equivalent

Yearly Total Human-Induced Net CO₂ Emissions