The 1.5°C threshold will be exceeded in the coming years, UN warns

Global warming is set to exceed the +1.5°C threshold above pre-industrial levels, the most ambitious limit set by the Paris Agreement. This is according to a new report by the United Nations Environment Programme (UNEP), which warns that the threshold could be crossed as early as the coming years.

In the most favourable scenario, the rise in global temperature would stop at +1.8°C. Most other projections point to higher values. The effects of climate change will become more severe, more frequent and harder to contain, affecting agriculture, water resources and ecosystems.

According to experts, it is nonetheless still possible to limit the duration and extent of the overshoot and bring temperatures back below the 1.5°C threshold as quickly as possible.

The three phases outlined in the report

The report, titled "Limiting Overshoot", proposes a path in three phases: overshoot, peak and subsequent reduction. This is considered the most effective strategy to contain the effects of warming and shorten the time spent above the Paris limit.

Achieving it would require immediate and sustained cuts to greenhouse gas emissions, together with measures to remove carbon dioxide from the atmosphere and store it, such as CO2 capture and storage technologies and reforestation.

Climatologist Luca Mercalli points to the limits of these solutions. Capturing CO2, he explains, is "estremamente complessa" ("extremely complex"), and the available technologies are still at an early stage of research: only small pilot plants exist so far, constrained by the amount of energy needed to run them. There is therefore currently no technology applicable on a large scale to remove the billions of tonnes of CO2 required from the atmosphere.

Reforestation, Mercalli says, "ha il vantaggio che funziona subito" ("has the advantage of working immediately"), thanks to photosynthesis. But it is no miracle solution: it would require enormous areas of land, and trees, "esseri viventi e non macchine, patiscono anche loro il riscaldamento globale" ("living beings, not machines, also suffer from global warming"), too. During heatwaves and droughts they metabolise less CO2 and can even stop altogether. Recent wildfires in Canada and Europe also show how fragile forests remain in the face of climate change.

UN Secretary-General António Guterres said: "Il caldo torrido, gli incendi devastanti e le inondazioni letali di quest'estate sono un avvertimento di ciò che ci attende" ("This summer's searing heat, devastating fires and deadly floods are a warning of what lies ahead"). He called on governments to raise the ambition of their climate policies.

Under current policies, the report warns, global warming could reach around 2.6°C by 2100. The consequences would include more frequent extreme weather events, melting glaciers and growing risks to ecosystems such as coral reefs. Questions remain over who will bear the cost of the necessary adaptations and how to protect the communities and sectors most exposed, from agriculture to water management.