A major study published on Wednesday warns that even temporarily exceeding the 1.5°C global warming limit could lead to irreversible consequences, including rising sea levels and mass biodiversity loss. With global emissions still rising, scientists stress that hopes of reversing climate overshoot without drastic action are dangerously misguided.
For years, scientists have held onto the hope that even if global temperatures temporarily exceed climate targets, the planet could eventually cool back down. However, a major academic study released on Wednesday has cast doubt on that idea.
The report highlights the dangers of "climate overshoot"– a temporary breach of the 1.5°C warming limit set in the 2015 Paris Agreement. While world leaders have committed to keeping the global temperature increase below 1.5°C, emissions continue to rise, making this goal increasingly difficult to achieve.
The study emphasises that even a brief overshoot could lead to long-term impacts, including rising sea levels and other lasting effects that may persist for thousands of years.
At the 2015 Paris Agreement, several strategies were agreed upon in order to meet climate goals, such as halving greenhouse gas emissions by 2030.
Yet, these pledges have not been matched by action, and the idea of overshoot has even been embraced by some world leaders as a fallback plan.
False promises
At the 2023 climate negotiations in Dubai, COP 28 President Sultan Al Jaber promised to uphold the 1.5°C goal, stating the United Arab Emirates was guided by a "deep sense of urgency".
However, as CEO of the Abu Dhabi National Oil Company (ADNOC), Al Jaber was simultaneously overseeing plans for a major expansion in fossil fuel production.
Read moreSultan al-Jaber under fire: COP28 president accused of conflict of interest
This is one of the many contradictions between public promises and private actions. Many policies claiming to align with the Paris Agreement’s 1.5°C target are underpinned by the flawed belief that climate overshoot can be reversed without radically reducing emissions or the removal of carbon dioxide from the atmosphere.
“Our research highlights that hoping to overshoot and then return to safer levels is delusional,” said Joeri Rogelj, a professor of climate science at Imperial College London and one of the co-authors of the study.
The research, spanning three years, outlines how exceeding the 1.5°C global temperature target could lead to consequences lasting for centuries.
The paper shows overshooting could trigger the thawing of permafrost, releasing vast amounts of greenhouse gases that would further accelerate climate change. Furthermore, it indicates that for every 100 years the temperature exceeds 1.5 °C, there is an associated increase in sea-level rise by approximately 40 cm by the year 2300, which presents a significant danger to island nations.
“Climate overshoot would leave an irreversible legacy,” said Carl-Friedrich Schleussner, lead author of the study and science advisor to Climate Analytics and Honorary Professor at Humboldt University Berlin. “It may not be reversible, even if global temperature increase might actually be reversed."
Irreversible consequences
The effects of even slight temperature increases are already visible. Rising sea levels have made coastal areas more vulnerable to flooding during storms, as seen in Florida, where sea levels have risen by eight inches since 1950.
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Additionally, the research points to extreme heatwaves that could result in excess deaths, especially in vulnerable communities. Each fraction of a degree above 1.5°C increases the risk of triggering climate tipping points, such as the collapse of the Amazon rainforest or the complete destruction of the coral reef.
"We need to develop safeguards against high-warming scenarios by building the capacity to remove carbon dioxide at scale, while simultaneously reducing emissions," Schleussner said. However, the technology needed to remove CO2 from the atmosphere on such a large scale is still not available.
Beyond physical climate changes, overshoot also poses a severe threat to biodiversity. The 2024 WWF Living Planet Report revealed an alarming 73% decrease in wildlife populations over the past 50 years. This decline underscores the urgency of addressing the climate crisis, as species extinction accelerates due to habitat loss and ecosystem collapse.
Read moreWorld's oceans close to becoming too acidic to sustain marine life, report says
A call to action
Achieving global climate and biodiversity targets requires immediate and bold action. Under the Paris Agreement, which operates on a five-year cycle, countries are due to submit updated national climate plans – known as Nationally Determined Contributions (NDCs) – in 2025.
"This will provide an opportunity to raise ambitions," said Rogelj, expressing cautious optimism. However, the study makes it clear that time is running out.
"It’s not just about reducing emissions or removing carbon dioxide from the atmosphere," added Schleussner. "We need to do both, as quickly and extensively as possible."
Overshooting the 1.5°C target is not a temporary setback, but, according to the study, a path towards lasting harm. The time for half-measures has passed – quick, coordinated global action is the only way to avoid the worst consequences of climate overshoot.
