.svg){kind=small}
Perhaps ‘freshly’ was not the right word to use here. For the better part of late May, the temperatures satisfied the conditions of being defined as a heatwave in the region: more than 35°C during the day, and not lower than 20°C during the night, for 3 days at least.
The heat dome was affecting most of Western Europe1. France is no stranger to searing heat during summer months, with more frequent and longer heatwaves since the beginning of the century2; however, this heatwave set a record during the month of May.
While heatwaves themselves existed before global temperatures increased above 1°C from pre-industrial levels, their characteristics (precocity, frequency, intensity and duration) are changing. Experiencing this firsthand was a reminder that for climate change risk, the past is not a good indicator of what the future holds.
One of the key ways to gauge the potential extreme weather events and their impacts on society is through climate scenario analysis, which relies on scenario archetypes from the IPCC3. The IPCC regularly refreshes scenarios, based on modelling and assumptions from current understanding of climate change science and policy settings.
In 2014, as part of their 5th assessment (AR5), the IPCC published the RCP4 scenarios, showing several futures with a link between the radiative forcing (from greenhouse gas emissions (GHG)) and temperature outcomes. These scenarios were focused on the physical world (GHG concentration and temperatures).
In 2021 (for its 6th assessment (AR6), the SSP5 scenarios were presented. They represented different paths of society, especially with regard to state cooperation and energy availability and sustainability.
The two scenario families are often considered together as greater societal cohesion is associated with stronger emissions mitigation.
In view of the next assessment report (AR7) in the next few years, work is already well underway for the scenario framework describing the refreshed scenarios.6 Several scenarios are designed to cover emission profiles:
The new scenarios take into account renewable energy costs, current climate policies and overall emissions trends. As a result, the RCP8.5 scenario (aligned with a hothouse world) is no longer considered as plausible. RCP1.9 (which is 1.5°C aligned) seems to stay as an aspirational scenario, as we see in the AR7 “Low to Negative emissions” scenario.
Some observers interpreted the reduced prominence of scenarios such as RCP8.5 as evidence that earlier climate assessments overstated risks. In reality, the change reflects updated assumptions regarding technology costs, policy developments and observed emissions trajectories rather than a revision of the underlying science.
For entities undertaking climate scenario analysis though, this may not necessarily mean that the hothouse world scenario considerations cease to be decision-useful.
Quantitative analysis may need to eventually use the macroeconomic parameters of the AR7 scenarios, when they are available. It may take time to downscale from the scenarios; in the meantime, it would be prudent to keep the assumptions as they were to determine anticipated impacts or Climate Value at Risk.
Qualitative analysis on the other hand would not necessarily be impacted, as the hothouse scenario is used to assess the resilience of the entity against a deterioration of the physical environment and stalling climate policies. As seen above, the “High emissions” scenario may serve a similar purpose to RCP8.5.
It is a good reminder that climate change risk is a deeply uncertain risk, and that perfect information is not available. Climate scenario analysis is therefore not an exercise in predicting the future with precision.
Rather, it is a structured way to explore uncertainty, identify vulnerabilities and support decisions that enhance resilience across a range of plausible futures.
Perhaps ‘freshly’ was not the right word to use here. For the better part of late May, the temperatures satisfied the conditions of being defined as a heatwave in the region: more than 35°C during the day, and not lower than 20°C during the night, for 3 days at least.
The heat dome was affecting most of Western Europe1. France is no stranger to searing heat during summer months, with more frequent and longer heatwaves since the beginning of the century2; however, this heatwave set a record during the month of May.
While heatwaves themselves existed before global temperatures increased above 1°C from pre-industrial levels, their characteristics (precocity, frequency, intensity and duration) are changing. Experiencing this firsthand was a reminder that for climate change risk, the past is not a good indicator of what the future holds.
One of the key ways to gauge the potential extreme weather events and their impacts on society is through climate scenario analysis, which relies on scenario archetypes from the IPCC3. The IPCC regularly refreshes scenarios, based on modelling and assumptions from current understanding of climate change science and policy settings.
In 2014, as part of their 5th assessment (AR5), the IPCC published the RCP4 scenarios, showing several futures with a link between the radiative forcing (from greenhouse gas emissions (GHG)) and temperature outcomes. These scenarios were focused on the physical world (GHG concentration and temperatures).
In 2021 (for its 6th assessment (AR6), the SSP5 scenarios were presented. They represented different paths of society, especially with regard to state cooperation and energy availability and sustainability.
The two scenario families are often considered together as greater societal cohesion is associated with stronger emissions mitigation.
In view of the next assessment report (AR7) in the next few years, work is already well underway for the scenario framework describing the refreshed scenarios.6 Several scenarios are designed to cover emission profiles:
The new scenarios take into account renewable energy costs, current climate policies and overall emissions trends. As a result, the RCP8.5 scenario (aligned with a hothouse world) is no longer considered as plausible. RCP1.9 (which is 1.5°C aligned) seems to stay as an aspirational scenario, as we see in the AR7 “Low to Negative emissions” scenario.
Some observers interpreted the reduced prominence of scenarios such as RCP8.5 as evidence that earlier climate assessments overstated risks. In reality, the change reflects updated assumptions regarding technology costs, policy developments and observed emissions trajectories rather than a revision of the underlying science.
For entities undertaking climate scenario analysis though, this may not necessarily mean that the hothouse world scenario considerations cease to be decision-useful.
Quantitative analysis may need to eventually use the macroeconomic parameters of the AR7 scenarios, when they are available. It may take time to downscale from the scenarios; in the meantime, it would be prudent to keep the assumptions as they were to determine anticipated impacts or Climate Value at Risk.
Qualitative analysis on the other hand would not necessarily be impacted, as the hothouse scenario is used to assess the resilience of the entity against a deterioration of the physical environment and stalling climate policies. As seen above, the “High emissions” scenario may serve a similar purpose to RCP8.5.
It is a good reminder that climate change risk is a deeply uncertain risk, and that perfect information is not available. Climate scenario analysis is therefore not an exercise in predicting the future with precision.
Rather, it is a structured way to explore uncertainty, identify vulnerabilities and support decisions that enhance resilience across a range of plausible futures.
