On December 12, 2015, exactly ten years ago, nearly 200 countries signed the Paris Agreement, a historic pact to tackle climate change. It was formalized on April 22, 2016, when it opened for signatures in New York (Earth Day), and officially entered into force on November 4, 2016, after the required number of ratifications was achieved. Its goal was to keep the increase in global average temperature “well below 2°C above pre-industrial levels,” while also aiming to limit it to 1.5°C.
Another objective was to strengthen countries’ capacity to adapt to the impacts of climate change and provide financial and technological support to developing nations for the transition to low-carbon economies.
By signing, countries committed to submitting national climate action plans (NDCs) and updating them every five years.
Since then, the world has changed significantly. Days before COP30, UN Secretary-General António Guterres admitted that “exceeding the 1.5°C threshold, at the latest in the early 2030s, is now inevitable.”
The most comprehensive assessment of the global environmental situation ever conducted calls on countries to adopt a unified approach to tackle the most pressing environmental crises: climate change, biodiversity loss, and pollution, which threaten over one million plant and animal species with extinction.
The report was compiled this week by the UN Environment Assembly (UNEA)—a session in which the United States did not participate. Nearly 300 scientists from 83 countries contributed, making it the largest and most comprehensive assessment of its kind.
Linked Crises Require Joint Solutions
The crises examined in the report—from land degradation and deforestation to air and water pollution—are closely interconnected and require joint solutions. The authors of the Global Environment Outlook emphasize that real progress requires:
- Increased investments
- Strong economic incentives to reduce reliance on fossil fuels
- Promotion of sustainable agricultural practices
- Reduction of pollution and resource waste
“You cannot talk about climate change without also addressing biodiversity, land degradation, and pollution,” explains Bob Watson, one of the lead authors and former chief scientist at NASA and the UK government.
“And you cannot examine biodiversity loss without considering the impacts of climate change and pollution.”
Despite dramatic warnings, scientists note that international cooperation is weakening—mainly because U.S. President Donald Trump refuses to participate in many critical discussions.
Trump, who withdrew the U.S. from the Paris Agreement, has called climate change a “hoax,” promoted fossil fuels, revoked renewable energy permits, and abandoned fuel efficiency standards for vehicles. “If the U.S. does not want to act, why should we?” some countries seem to ask.
The Hottest Decades in History
Data from the Copernicus Climate Change Service (C3S) and Copernicus Atmosphere Monitoring Service (CAMS) show that 2015–2024 is the hottest decade on record. If temperatures for November and December 2025 remain high, this year will rank as the second or third hottest since measurements began. “Ten years after the Paris Agreement, the planet is hotter than ever. Every year since 2015 ranks among the 10 hottest recorded,” says Carlo Buontempo, director of C3S.
“It is now clear that the climate is changing at a pace humanity has never experienced.”
For the first time, C3S notes, it is likely that the 1.5°C threshold could be exceeded within the next three years.
How Close Are We to 1.5°C?
When the Paris Agreement was signed in December 2015, Copernicus data indicated global warming had reached 1.04°C above pre-industrial levels, with the 1.5°C threshold projected for 2042.
As of September 2025, warming is estimated at 1.4°C, and Copernicus trends suggest the 1.5°C limit could be reached around 2029.
In other words, a decade ago, the 1.5°C milestone was projected 27 years away. Now, it is only four years away.
Scientists emphasize that the rapid acceleration of warming is linked to rising concentrations of greenhouse gases, making it more difficult to keep temperatures below 1.5°C.
Efforts and Progress
However, there has also been progress. Many countries have significantly increased renewable energy production. Solar and wind power have become economically competitive and are expanding rapidly, while electric mobility is growing exponentially.
More than 190 countries have submitted national climate action plans (NDCs), committing to reduce greenhouse gas emissions. Some countries, such as the EU, have set net-zero targets for 2050. However, developing nations require greater financial and technological support to implement mitigation and adaptation measures. Funding promises have not yet been fully realized.
The Paris Agreement has strengthened global cooperation, with regular COP meetings monitoring implementation and encouraging enhanced commitments.
In 2015, the UN Emissions Gap Report projected a “baseline” warming of 4°C by 2100 if no action was taken. Today, according to the latest report, the world is heading toward 2.8°C under current policies, and 2.3–2.5°C if all countries fully implement their NDCs.
Rising Emissions and Gas Concentrations
Greenhouse gas emissions have continued to rise since 2015. In 2024, CO₂ concentrations reached a record high, the largest annual increase since 1957, according to the World Meteorological Organization.
Since the Paris Agreement, CO₂ levels have risen 5.51%, reaching 422 ppm in December 2024. Methane increased 4.86%, reaching 1,897 ppb that same month. “Our atmosphere is the most immediate indicator of our actions,” explains Laurence Rouil, CAMS director.
“Over the past ten years, CO₂ concentrations have risen over 5%, reaching the highest annual levels ever recorded.”
Fossil fuel emissions accounted for nearly 75% of total carbon emissions in 2024, while 2025 fires released more than 1.3 billion tons of carbon, simultaneously degrading air quality and affecting health.
Extreme Temperatures as the New Reality
Heatwaves have become more likely since 2015. According to a joint study by Climate Central and World Weather Attribution, countries now experience an average of 11 more hot days per year than in the decade before the Paris Agreement.
The study analyzed selected extreme temperature events from each continent. Three of these events would have been impossible without human-induced warming, while two were roughly ten times more likely in 2025 than in 2015.
For example, a one-week heatwave in Southern Europe in 2023 is now 70% more likely and 0.6°C hotter than a decade ago, while in pre-industrial conditions it would have been almost impossible.
Climate Crisis as a “Risk Multiplier”
Climate change does not only exacerbate extreme weather. It acts, as Texas Tech professor and Nature Conservancy lead scientist Katharine Hayhoe explains, as a “threat multiplier”: worsening phenomena such as land degradation, deforestation, and biodiversity loss. m“If we do not solve climate change, we will not be able to solve the other problems either,” she stresses.
Globally, up to 40% of land is now considered degraded, while pollution is responsible for roughly 9 million deaths annually.
The past decade has brought significant changes in how societies approach climate issues, but implementation remains slow and uneven. The Paris Agreement remains a reference point, yet achieving its goals requires accelerated action, greater funding, technological innovation, and decisive policy interventions.
