datalab
Key figures on climate
France, Europe and Worldwide
2023 EDITION
lang

Climate scenarios and projections

Projections of CO2 emissions according to the five IPCC scenarios

Note: the last numbers (1.9, 2.6, 4.5, 7.0 and 8.5) naming each trajectory correspond to the radiative forcings induced by 2100 compared with the pre-industrial era, expressed in W/m2.
Source: IPCC, 1st working group, 2021

The IPCC published its first report (First Assessment Report) in 1990. The first volume of its sixth report (AR6) was published in August 2021. With each publication, the IPCC communicates climate projections based on GHG concentration assumptions and presents the state of scientific knowledge on climate change.

A core set of five scenarios based on shared socio-economic trajectories (SSPs) is used consistently in the 6th IPCC Assessment Report (AR6). These scenarios cover a range of GHG emission trajectories, from low with climate change mitigation to high. For example, the SSP1-2.6 scenario corresponds to sustainable development that would limit temperature rise to 1.8°C by the end of the century. The worst-case scenario (SSP5-8.5) would lead to a rise of 4.4°C.

Methane (CH4), the second major component of greenhouse gases

Note: monthly averages of air samples taken from the world's marine surfaces.
Source: National Oceanic and Atmospheric Administration (NOAA), USA, 2023

The average atmospheric concentration of methane in 2022 is 1.91 ppm (NOAA preliminary estimate), around 220 times less than that of CO2 . However, its global warming potential (GWP, see glossary) is 84 times greater than that of CO2 during the first 20 years following its emission. More than a quarter of global warming since pre-industrial times could be attributed to methane. The increase in methane emissions has accelerated in recent years, including during the Covid-19 pandemic.

CH4 emissions projections according to the five IPCC scenarios

Source: IPCC, 1st working group, 2021

Temperature and sea-level evolution according to the five IPCC scenarios
Projected global mean temperature change compared with the period 1850-1900

Source: IPCC, 1st working group, 2021

Projected average sea level rise compared with 1900

Note: solid lines show median projections. Shaded areas show probable ranges for SSP1-2.6 and SSP3-7.0. The dotted line (83rd percentile) indicates a maximum, albeit low-probability, impact of the SSP5-8.5 scenario on sea levels.
Source: IPCC, 1st Working Group, 2021

The main factors driving sea-level rise (see p.14) are thermal expansion of the oceans and melting of land-based ice reservoirs (glaciers, polar ice caps, etc.). By 2100, mean sea levels will have risen by between 0.28 and 0.55 m relative to the 1995-2014 average under the sustainable development scenario (SSP1-2.6), and by between 0.63 and 1.02 m under the worst-case scenario (SSP5-8.5). Rising sea levels are likely to cause major population migrations, as over a billion people live in coastal lowlands (less than 10 meters above sea level).

Carbon budgets and rising temperatures

The remaining carbon budget corresponds to a maximum amount of CO2 emissions for which there is a reasonable probability of avoiding average temperatures rising above a certain level. Only the most ambitious trajectories in terms of climate change mitigation efforts (SSP1-1.9 and SSP1-2.6) could limit the rise in temperatures to 1.5°C and 2°C respectively by 2100. In 2021, the UN assessed that the commitments made by the parties to the Paris Agreement place the world on SSP2-4.5, which is associated with a temperature rise by 2100 of between 2 and 2.9°C compared with the period 1850-1900.

Remaining carbon budget to limit the average temperature increase to 1.5°C and 2°C

Note: values are expressed as a percentage of the total carbon budget since pre-industrial times, obtained by comparing cumulative emissions between 1850 and 2021 (Friedlingstein et al., 2022) with the carbon budget remaining from 2019 (IPCC, 2021). Carbon budgets are given with a 67% probability of meeting the associated climate target (1.5°C or 2°C). Uncertainty scales concerning carbon budgets are high, in the order of ± 3.7 Gt CO2 . They stem in particular from uncertainties concerning the evolution and impact of greenhouse gases other than CO2 , the reactions of the climate system to increasing cumulative emissions and radiative forcing, and the reactions of the Earth system to rising temperatures.
Sources: I4CE, based on Friedlingstein et al, Global Carbon Budget 2021, 2022; IPCC, 1st Working Group, 2021

To limit the average temperature rise to 2°C compared with the pre-industrial era with a 67% probability, the remaining carbon budget from 2021 is 1,075 Gt CO2, and only 325 Gt CO2 to limit the rise to 1.5°C (IPCC, 2021). If CO2 emissions continue to grow at this rate, the remaining carbon budget, which would with two chances out of three enable us to limit the temperature rise to 2°C, will be exhausted before 2050. To limit the rise to 1.5°C, it will be exhausted within the next ten years only (IPCC, 2022).

Consequences for the world
Historical emissions and projections according to GHG emission scenarios

Source: IPCC, 6th report, 2022

The figure illustrates past and future changes in climate. The scenarios of very low (SSP1-1.9), low (SSP1-2.6), intermediate (SSP2-4.5), high (SSP3-7.0) and very high (SSP5-8.5) GHG emissions are used to obtain future projections (2021-2100) of global surface temperature changes.

Current global policies (high and very high scenarios) would lead to a median warming of+3.2°C by 2100 (IPCC, 2023). If they are respected, the commitments made to date by States at the climate COPs would make it possible to contain the rise in temperature to around 2.8°C (from 2.1 to 3.4°C) by the end of the century. Global warming will continue beyond 2100, except for low and very low GHG emission scenarios.

Consequences for France
Annual soil moisture cycle

1961-1990 average, records and climate simulations for two time horizons (evolution scenario corresponding to current trajectory)

Scope: metropolitan France.
Source: Climat HD, Météo-France

A comparison of the annual soil moisture cycle in France between the 1961-1990 climatic reference period and the near (2021-2050) or distant (2071-2100) time horizons of the 21st century (according to a scenario corresponding to the current trajectory) points to significant drying out in all seasons.

In terms of potential impact on vegetation and non-irrigated crops, this evolution translates into an average lengthening of the dry soil period by around 2 to 4 months, while the wet period is reduced in the same proportions. Average soil moisture at the end of the century could thus correspond to today's extreme dry conditions.