Scientific evidence on the extent and acceleration of global warming, as well as the anthropogenic role driving it, is accompanied by increasingly severe consequences for the environment and socio-economic systems. This highlights an emergency situation that is endangering the health and well-being of the global population [1].

The brief excerpt provided here, referring to the Trentino Provincial Strategy for Climate Change Adaptation, highlights two key aspects of the topic: (1) scientific evidence and (2) the anthropogenic role.

Indeed, while the historical outcome of climate change — why it occurs and where it has brought us — is now clear, scientifically proven, and widely accepted, the analysis of the future that awaits us is more neglected. Specifically, questions remain about how, and if, climate change will evolve in the coming decades and what will drive this evolution.

This type of analysis can only be based on mathematical-statistical models capable of projecting what the future holds. A sort of modern version of the crystal ball, but based on data, algorithms, and degrees of uncertainty, and therefore heavily dependent on a potentially infinite number of variables.

Let us not delude ourselves into predicting the future like Nostradamus; such an approach would not be scientifically acceptable. However, we can at least attempt to outline guidelines, probabilities of occurrence, and mathematical methods to determine what the climate of the future will be. In essence, we aim to define what translates into climate change scenarios [2].

What is a scenario?

A scenario is a plausible description of how the future might unfold, based on consistent and coherent determining factors, such as the level of technological change, market and price evolution, and the adoption of strategies for mitigating and adapting to climate change.

What does a scenario describe?

Different scenarios describe different factors. Regarding the future climate, the most relevant are: (1) Concentration scenarios, which describe the future development of atmospheric concentrations of radiatively active substances such as greenhouse gases and tropospheric ozone, as well as those resulting from human-induced land use changes; (2) Emission scenarios, which describe the future development of emissions of these same substances, based on various projections of technological, socio-economic, and energy development capable of influencing those emissions.

However, a common factor in all of this remains the baseline scenarios, which serve as a reference for comparisons with other scenarios. Often, the baseline scenario is represented by the historical state of the phenomenon or by the assumption that the phenomenon will not change in the future. A classic example of this is the projection of future development without climate policies, based on the same development model adopted over the past century or recent decades.

Conversely, Mitigation scenarios describe how the system under consideration will respond in the future to specific mitigation measures and policies, at varying degrees of stringency.

Finally, socio-economic scenarios describe a possible future solely in terms of Gross Domestic Product (GDP) and other relevant social and economic variables that are important in describing and understanding the implications of climate change.

In practice, the Shared Socio-economic Pathways (SSPs) are among the most widely used scenarios that describe possible future developments based on the anthropogenic drivers of climate change [3]:

• SSP1: Sustainable development and a “green” path for the entire world.
• SSP2: “The middle of the road”. The past and current development model are carried into the future, with moderate population growth and significant differences between countries.
• SSP3: Regional rivalry. Regional and national conflicts overshadow sustainable development goals and global issues.
• SSP4: The gap and differences between highly developed countries and developing or less developed nations increase. Environmental issues are addressed only at the local level.
• SSP5: Development based on fossil fuels.

How is a climate scenario constructed?

A climate scenario can be described as a projection, determined by a model, that simulates the climate’s response to a specific emissions or concentration scenario. Even in this case, a climate projection does not represent a prediction or forecast (like weather forecasts), as it is not based on actual evidence of certain future events but solely on the assumptions underlying the scenarios used to build the projection. In practice, climate projections describe how various climate parameters (such as temperature, precipitation, snowfall, humidity, etc.) will behave in the future, based on the scenarios that drive them. These projections are often spatially explicit, meaning they are determined with precision for a specific location, such as a region, a province, a country, or even a small and geographically defined area.

Fig. 1: Trentino-Alto Adige: Climate scenario for the variable “Mean Annual Air Temperature” for the period 1981-2010 (on the left) and the projection for the period 2071-2100, SSP5 (on the right). Source: own elaboration from CHELSA data [4]

Some examples

For Trentino [5], across the range of scenarios developed, the projections highlight that average annual temperatures will increase at least until 2050, with an expected average rise between 1 °C and 2 °C depending on the emissions scenario considered. This implies an expected increase in the frequency and intensity of heatwaves.

Precipitation is expected to increase in intensity but decrease in the number of rainy days compared to the reference period 1981-2010.

Finally, the number of days with snow on the ground is expected to decrease across the entire Alps, with a reduction ranging from 20 to 48 days compared to the period 2001-2020, depending on altitude.

This information is essential for planning sustainable development across the entire territory. The strategies outlined in various territorial development programs and plans make extensive use of these scenarios and simulations. Water consumption and withdrawals, linked to the efficiency of water networks, the conservation status of habitats and species, air quality in relation to climate-altering emissions, and territorial safety concerning natural hazards are all directly influenced and guided by anticipated climate changes.

Studying and attempting to simulate the future climate can, therefore, be an effective tool to guide the development, growth, and planning of tomorrow’s territories.

This article is part of the project “Quiz Ambientali per un Trentino Più Verde!” carried out by Econtrovertia APS and sponsored by Fondazione Cassa Rurale di Trento (Notice of Approval of December 20, 2024).

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