Scientists Say World Will Exceed 1.5°C Warming Limit

The world has now effectively entered a new and dangerous climate era, with top scientists and global data agencies confirming that the planet’s temperature rise has breached the 1.5°C warming limit on a sustained, multi-year basis. Data from 2024 marked the first full calendar year to average over 1.5°C, and new 2025 reports from the UN’s weather and emissions bodies warn this threshold is no longer a future risk, but a current reality that must be managed.

This sobering consensus forms a dark backdrop to the COP30 climate summit in Belém, where leaders are grappling with the reality that the primary goal of the 2015 Paris Agreement—to prevent 1.5°C of warming—has been missed. The global focus is now shifting from prevention to a desperate race to manage a “climate overshoot,” a period of higher temperatures that scientists warn will inflict irreversible damage on the planet, even if warming can be brought back down later this century.

Quick Take: The State of the 1.5°C Limit

Here are the key facts driving the global conversation in late 2025:

• First 1.5°C Year: The 2024 calendar year was the first in recorded history to average more than 1.5°C above pre-industrial levels, finishing at 1.60°C warmer.
• Sustained Breach: The World Meteorological Organization (WMO) reported in May 2025 there is a 70% likelihood the entire five-year average for 2025-2029 will exceed the 1.5°C threshold .
• More Records Imminent: The WMO also calculated an 86% chance that at least one year between 2025 and 2029 will set a new global temperature record, beating 2024.
• Record Emissions: This warming is driven by record-high global greenhouse gas emissions, which hit 57.7 billion tonnes of CO2 equivalent in 2024.
• The Policy Gap: The 2025 UNEP Emissions Gap Report, released just days ago, finds that even if all countries fully meet their current climate pledges, the world is on track for 2.3°C to 2.5°C of warming this century.

A Red Line Crossed: The Data on a Record-Breaking Period

For years, the 1.5°C warming limit was a political guardrail—a line in the sand that scientists warned must not be crossed to avoid the most catastrophic and irreversible impacts of climate change.

That line is now in the rearview mirror, at least temporarily.

The breach began in mid-2023 during the onset of a strong El Niño event, but it did not relent as expected. The EU’s Copernicus Climate Change Service (C3S) confirmed in early 2025 that the 2024 calendar year was the warmest on record, at 1.60°C above the 1850-1900 pre-industrial average. This was not an isolated spike. The 12-month period from February 2024 to January 2025 averaged 1.61°C above the baseline.

While the Paris Agreement technically refers to a 20-year average—meaning the permanent breach is not yet official—scientists are blunt that this distinction is now a semantic one. A May 2025 report by the World Meteorological Organization (WMO) shattered any remaining optimism. It concluded that the five-year mean temperature for 2025-2029 is 70% likely to be above 1.5°C.

“We are playing Russian roulette with our planet,” UN Secretary-General António Guterres said in June 2024, reacting to the WMO data. “We need an exit ramp off the highway to climate hell.”

By November 2025, with leaders gathered in Brazil for the COP30 talks, his tone had turned to one of grim acceptance. He told delegates that missing the 1.5°C target was a “moral failure and deadly negligence,” warning that even a temporary overshoot could “push ecosystems past catastrophic tipping points.

The ‘Policy and Emissions Gap’: Why 1.5°C Failed

The scientific data is unambiguous, and so is the reason for the failure: a persistent and massive gap between political promises and real-world action.

Just days ago, the UN Environment Programme (UNEP) released its “Emissions Gap Report 2025,” an annual assessment that measures the difference between where emissions are heading and where they should be.

The findings are stark. Global greenhouse gas (GHG) emissions, including from land-use change, hit a new record of 57.7 billion tonnes (GtCO2e) in 2024. While some major economies like China may be near their peak, the global trajectory is nowhere near the sharp downturn required.

The report finds that under current policies, the world is on track for 2.8°C of warming. Even in the most optimistic scenario, where all nations fully and perfectly implement their Nationally Determined Contributions (NDCs), warming is projected to be between 2.3°C and 2.5°C.

This confirms that the pledges made in Paris and updated in Glasgow and Dubai were, as many scientists feared, simply not enough.

Analysis: The Dangerous New Era of ‘Climate Overshoot’

With the 1.5°C prevention goal lost, the scientific and policy debate has pivoted to a far more perilous concept: “overshoot.”

This is the consensus scenario now being modeled by the Intergovernmental Panel on Climate Change (IPCC) and other leading bodies. The strategy involves a period where global temperatures will exceed 1.5°C—peaking somewhere between 1.6°C and 1.9°C—before (it is hoped) being brought back down by the end of the century through massive-scale carbon dioxide removal (CDR) from the atmosphere.

Irreversible Scars: Why ‘Returning’ Isn’t a Reset

A critical, and often misunderstood, part of the overshoot scenario is that it is not a simple “undo” button. The world that returns to 1.5°C in the year 2100 will be a fundamentally different and more damaged planet than one that never crossed the threshold at all.

According to a 2025 analysis on overshoot scenarios, the impacts are deeply concerning.

1. Irreversible Tipping Points: Even a temporary overshoot of a few decades can trigger permanent changes. This includes the irreversible loss of keystone species, the collapse of critical ecosystems like coral reefs (which cannot survive the sustained heat), and the potential destabilization of parts of the Greenland and West Antarctic ice sheets, locking in meters of future sea-level rise.
2. Ecosystem Disruption: As one expert in the report noted, “Extinct species don’t come back because temperatures decline.” Food webs that are disrupted may never re-form in the same way, permanently altering biodiversity.
3. Compounding Social Harm: The human impacts of overshoot are not easily reversed. A decade of intensified droughts, floods, and heatwaves will drive multi-generational poverty, malnutrition, and land degradation. These vulnerabilities become entrenched in societies, and “vulnerability would remain likely much higher” even after temperatures theoretically stabilize.

Essentially, the world is now committing to a period of known high damage, betting on unproven, large-scale technologies like Direct Air Capture (DAC) to clean up the mess later.

Is 1.5°C Still Alive? The ‘Highest Possible Ambition’ Path

Despite the grim data, scientists at COP30 are fiercely arguing against “doomerism.” The consensus is that while the 1.5°C limit is breached, the 1.5°C goal remains the vital benchmark for limiting the duration and magnitude of the overshoot.

Every fraction of a degree matters.

A new report from Climate Analytics, an independent science institute, outlines a “Highest Possible Ambition” scenario. It argues that a return to “well below 1.5°C” by 2100 is still possible

This scenario, however, requires a truly radical, emergency-level global response:

• Global CO2 emissions must reach net-zero by 2045 (a decade earlier than many current targets).
• Global GHG emissions (including methane) must reach net-zero by the 2060s.
• This would limit peak warming to around 1.7°C before temperatures begin to slowly decline, driven by a rapid fossil fuel phase-out and the scaling of over 5 billion tonnes of CO2 removal per year by 2050.

“Overshoot of 1.5°C is a woeful political failure and will bring increased damages and risk of tipping points that otherwise could have been avoided,” said Bill Hare, CEO of Climate Analytics, in a statement accompanying the report. “But this roadmap shows it is still within our power to bring warming back well below 1.5°C by 2100.”

There is one bright spot in this otherwise dark forecast. “The last five years have cost us precious time,” noted Dr. Neil Grant, a climate expert at the institute. “However, they have also seen a revolution in renewables and batteries, which have shattered records… Riding these tailwinds can help turbocharge our clean energy future and catch-up on lost time.

Conclusion: What to Watch Next

As the negotiations in Belém, Brazil, enter their final days, the mood is one of grim determination. The failure to hold the 1.5°C line has forced a global reckoning.

The key items to watch are no longer just about emissions cuts; they are about managing the crisis. This includes:

1. Fossil Fuel Phase-out: Whether nations will finally commit to a “rapid, full, and fair” phase-out of all fossil fuels, which the science now shows is non-negotiable.
2. Carbon Removal (CDR): A massive, public- and private-sector push to fund and deploy CDR technologies, moving them from pilot projects to a global-scale industry.
3. Adaptation & Loss and Damage: With severe impacts now locked in, funding for poorer nations to adapt and to recover from unavoidable “loss and damage” has become a central, make-or-break issue at COP30.

The world of 2015, which hoped to prevent 1.5°C, is gone. The world of 2025 must now learn to survive the overshoot—and fight to ensure it is as short and as shallow as humanly possible.