Ten years after the Paris Agreement entered into force, the world has blown past the 1.5C limit the pact was written to defend. In 2024 the planet was more than 1.5C warmer than preindustrial levels across a full calendar year for the first time, and 2023 to 2025 were the hottest three years on record. In October 2026, UNEP said the chance of keeping warming to 1.5C without overshoot has been lost.

Key Points

• The Paris Agreement entered into force on 4 November 2016, aiming to hold warming well below 2C and limit it to 1.5C.
• 2024 was the first full year more than 1.5C above preindustrial levels, and 2023-2025 were the hottest three years on record.
• The long-term warming average now stands at about 1.4C, and scientists expect it to pass 1.5C around the end of this decade.
• UNEP said in October 2026 that the chance of staying under 1.5C without overshooting it has been lost.
• Policies at signing pointed to about 3.6C of warming by 2100; that projection has fallen to about 2.6C, but progress has stalled since 2021.

What Happened

The tenth anniversary of the Paris Agreement's entry into force fell on 4 November. Adopted by 196 parties at COP21 in Paris on 12 December 2015, it bound nearly every country to hold warming well below 2C and pursue efforts to limit it to 1.5C. Today, 194 parties, 193 countries plus the European Union, belong to it.

The milestone arrived with a blunt UN verdict. The long-term average now stands at about 1.4C, and scientists expect it to pass 1.5C around the end of this decade. The 2024 breach and the 2023-2025 three-year average above 1.5C show how fast the margin closed. The deal rests on voluntary pledges, not binding cuts, with countries expected to raise ambition every five years.

Background and Context

When the agreement was signed, existing policies put the world on course for about 3.6C of warming by 2100. That projection has fallen to about 2.6C, according to Climate Action Tracker, as clean energy expanded faster than forecast. The pact did not deliver 1.5C, but it changed the trajectory of the century by roughly a full degree.

Progress, however, has stalled since 2021. Global emissions are 9 percent higher than in 2016. China, the United States and India now produce more than half of annual emissions, and China alone emits more than the United States, India, Russia and Japan combined, although the United States has released the most carbon historically. The United States, the world's second-largest emitter, has joined and left twice: President Donald Trump ordered the first withdrawal, effective November 2020; President Joe Biden rejoined in February 2021; and the United States left again in January 2026.

Paris Agreement at 10: What the Pact Changed and What It Did Not

The Paris Agreement changed the language of climate politics. Before 2015, international climate talks were defined by deadlock over who should cut emissions first. The Paris deal replaced that standoff with a system in which every country sets its own target and reports on its progress, backed by a shared temperature goal. That framework survived the American withdrawals.

It also changed the economics of energy, driving the fastest build-out of clean power in history. What it did not change was the speed of the transition. Emissions kept rising for most of the decade, and the world now lives with the consequences the agreement was meant to prevent: the deadly floods, heatwaves and wildfires seen this year. No country could be compelled to move faster, and pledges outran delivery.

Reactions and Quotes

UNEP Executive Director Inger Andersen warned that every additional fraction of a degree increases climate impacts and risks, pointing to the deadly floods, heatwaves and wildfires seen this year as evidence of what is already at stake. Her message: losing 1.5C makes further action more urgent, not pointless, because the difference between 1.6C and 2C is measured in lives, harvests and coastlines.

Climate researchers stress that overshooting 1.5C is not the same as abandoning the agreement. The goal was always framed as holding warming well below 2C while pursuing efforts to limit it to 1.5C, and the lower figure was a stretch target even in 2015.

Why It Matters

The loss of 1.5C matters because the number was never arbitrary. It was the threshold that small island states and the most vulnerable countries fought for in Paris, arguing that the difference between 1.5C and 2C was the difference between survival and disappearance for their homes. Passing it means more sea-level rise, heat, crop failures and displacement than promised.

It also matters because the agreement was the closest the world has come to a shared climate plan. If its central goal is now out of reach, governments must explain what replaces it. For the United States, the largest historical emitter and second-largest current one, the anniversary carries particular weight.

What Happens Next

The immediate question is what governments do with the next round of national pledges. Under the five-year cycle, countries must keep raising targets, and the gap between 2.6C on current policies and the well-below-2C goal measures the work remaining. The test will be whether the anniversary produces stronger commitments or becomes a moment of resignation.

The science also points to a longer road back. Even after the world passes 1.5C, deep and rapid cuts in emissions can bring temperatures down again over time, though some impacts, such as sea-level rise and the loss of glaciers, cannot be reversed on human timescales. The next climate summit will test whether the anniversary changes anything, and whether negotiators respond with faster cuts or new excuses.

Frequently Asked Questions

What is the Paris Agreement? The 2015 climate deal adopted by 196 parties at COP21 in Paris. It entered into force on 4 November 2016 and commits nearly every country to hold warming well below 2C and pursue efforts to limit it to 1.5C.

Has the world already passed 1.5C of warming? In 2024 the planet was more than 1.5C warmer than preindustrial levels across a full calendar year for the first time, and 2023-2025 averaged more than 1.5C. The long-term average is about 1.4C, expected to pass 1.5C around the end of this decade.

What did UNEP say in October 2026? The UN Environment Programme said the chance of keeping warming to 1.5C without overshooting it has been lost. Its executive director, Inger Andersen, warned that every additional fraction of a degree increases climate impacts such as floods, heatwaves and wildfires.

How much has the Paris Agreement changed the outlook? At signing, existing policies pointed to about 3.6C of warming by 2100. That projection has fallen to about 2.6C, according to Climate Action Tracker, though progress has stalled since 2021 and global emissions are 9 percent higher than in 2016.

Why did the United States leave the agreement? President Donald Trump ordered the first US withdrawal, effective November 2020. President Joe Biden rejoined in February 2021, and the United States left again in January 2026 under Trump.

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