Climate leaders are talking about ‘overshoot’ into warming danger zone. Here’s what it means

Climate Leaders Concede Planet Will Exceed 1.5°C Warming Limit, But Plan for Return

Global climate leaders have acknowledged that Earth’s temperature will inevitably rise beyond the critical 1.5 degrees Celsius warming threshold established in the 2015 Paris Agreement. However, they insist this breach doesn’t represent permanent defeat in the fight against climate change.

United Nations officials and scientists are now pivoting to a strategy called “overshoot” – allowing temperatures to temporarily exceed the limit before bringing them back down. This marks a significant shift from earlier rhetoric that treated the 1.5°C boundary as an absolute red line.

“The science is clear: We can and must bring temperatures back down to 1.5 Celsius after any temporary overshoot,” UN climate chief Simon Stiell stated at the climate conference currently underway in Belem, Brazil, situated in the Amazon rainforest.

UN Secretary-General Antonio Guterres was even more direct in his assessment last month: “Overshooting is now inevitable, which means that we are going to have a period, bigger or smaller, with higher or lower intensity, above 1.5 degrees in the years to come.” However, he emphasized, “That doesn’t mean that we are condemned to live with 1.5 degrees lost. No.”

The 1.5°C target refers to the average global temperature increase since pre-industrial times. Currently, the planet has warmed approximately 1.3°C, with 2023 already exceeding the 1.5°C mark for that single year. Scientists emphasize that the threshold is only officially breached when the 10-year average surpasses 1.5°C.

Johan Rockstrom, director of Germany’s Potsdam Institute for Climate Research, stressed the scientific importance of the threshold: “In Belem, we have more scientific evidence than we had 10 years ago that 1.5 is a real limit. It’s not a target, it’s not a goal, it’s a limit, it’s a boundary. Go beyond it, we increase suffering of people, and we increase risk of crossing tipping points.”

These tipping points represent potentially irreversible changes to Earth’s systems – including the collapse of coral reefs worldwide, increasingly deadly heat waves, the transformation of the Amazon rainforest into savanna, accelerated melting of polar ice sheets, and disruption of Atlantic Ocean currents that regulate global weather patterns.

Climate scientists have calculated that current policies put the world on track for approximately 2.6°C of warming, far beyond safe limits. According to analysis from Climate Action Tracker, even if every possible emission reduction measure were implemented immediately – something never achieved before – global temperatures would likely exceed 1.5°C around 2030, peak at about 1.7°C, and not fall back below the threshold until the 2060s.

The overshoot strategy hinges on two critical elements: dramatically cutting greenhouse gas emissions from fossil fuels and developing technologies to remove carbon dioxide already in the atmosphere. Once atmospheric carbon concentrations decrease, temperatures will eventually follow – though with a lag.

“Without carbon dioxide removal it is simply impossible to manage the overshoot scenario,” explained Ottmar Edenhofer, chief economist at the Potsdam Institute for Climate Research and chairman of the European Scientific Advisory Board on Climate Change.

The plan represents a fallback position after a decade of insufficient action. “Ten years ago we had a more orderly pathway for staying away from 1.5 Celsius entirely, basically with low or no overshoot,” Rockstrom noted. “Now we are 10 years later, we have failed.”

Scientists remain uncertain about exactly when and where the most dangerous climate impacts will manifest during the overshoot period, or whether a longer duration at slightly above 1.5°C is more dangerous than a shorter period at significantly higher temperatures.

What is clear is that the world’s current emissions trajectory points not toward a temporary overshoot but a complete failure to stabilize temperatures this century – a scenario that carries far greater risks for human societies and natural systems worldwide.