Paris Agreement decade: Climate optimism fades

BarcelonaHugs, cheers and applause greeted the birth of the Paris Agreement ten years ago. Years of painstaking negotiations had gone into its delivery during the COP21 climate summit in the French capital. Yet on 12 December 2015, every government in the world formally committed to preventing global warming from exceeding 2°C, and ideally keeping it below 1.5°C. The deal was far from perfect –not least because it was not legally binding– but that historic milestone of uniting 197 disparate governments was a Herculean task thatunleashed widespread optimism: the fight against the climate crisis had finally become an inescapable global goal.

A decade on, the global mood has shifted dramatically almost beyond recognition. Climate scepticism has roared back with unprecedented force, while the fossil fuel sector surges ahead unabated. The 1.5°C threshold above pre-industrial levels was breached – albeit briefly – in 2024, though not yet as a sustained long-term average, as the Paris Agreement sought to avert. CO₂ and other greenhouse gas emissions, expected to peak this decade, continue smashing records year on year. What has gone wrong?

Emissions

"The full impact of Donald Trump has yet to be felt; it begins now. But his actions are already prompting countries to stall climate efforts," says Olga Alcaraz, director of the Governmental Group on Climate Change at UPC. The professor laments that the EU is "following the US lead", struggling to secure agreement ahead of COP30, which opened this week in Brazil.

Ten years after Paris, governments must submit ambitious 2035 emissions targets at the Amazon summit. The EU has settled for its previous commitment – a 66.5% cut – after pushback from Hungary and Poland on a 90% by 2040 goal. "Von der Leyen's second term has a far weaker climate agenda. The 2019 Green Deal era sought leadership; now security trumps climate amid the Ukraine war," Alcaraz notes. "Back then –with the 2019 Green Dea – the EU sought climate leadership. Now security has taken priority amid the Ukraine war", points out Ricardo Martínez, senior analyst at CIDOB.

China, meanwhile, has seized green leadership and become the world's renewables superpower since Paris. "The Paris Agreement helped, but China saw renewables as a massive business opportunity," she says. "With central planning, Beijing has been planning each five-year economic cycle to promote renewables and now controls all the mineral resources of this industry", Alcaraz points out. Last month's Communist Party plenary approved the 2026-2030 plan to "establish green production and lifestyles" keeping China "on track for planned carbon peak targets", according to Beijing.

Beijing arrives at COP30 promising 7-10% emissions cuts by 2035 from its 2030 peak – a target first flagged years ago but now vaguely dated, as Alcaraz suggests it may come sooner. "It's highly unambitious for the world's top emitter, though China has a habit of under-promising then massively over-delivering," the expert notes.

By contrast, the US –second-largest emitter– pledged 50% cuts by 2030 under the Biden administration. But Trump scrapped it, quit Paris outright, and embraced his "drill, baby, drill" mantra.

The temperature

Yet despite its flaws, the Paris Agreement has delivered results. Pre-2015 projections pointed to 4°C of warming by century's end; COP30 commitments now put us on track for 2.5ºC if met --or 2,8ºC under current policies-, according to the latest UN report. Still insufficient, but progress nonetheless. Since Paris, global temperatures have risen from ~1°C to 1.3°C above pre-industrial levels. That 0.3°C jump alone has added 11 extra days of extreme heat annually (2025 vs 2015), according to a Climate Central study – with heat now the deadliest weather event, killing ~500,000 worldwide yearly.

t's still insufficient, but certainly an improvement. When that pact was signed, the global temperature was already around 1°C above pre-industrial levels, but we are now 1.3°C above. This change alone has added another eleven days of extreme heat per year (this year, 2025, compared to 2015), according to a Climate Central study. Heatwaves are now more frequent and intense than in 2015 –and far deadlier, killing ~500,000 people worldwide annually to become the world's most lethal weather event.

The 1.5°C red line looms closer, yet scientists say a reversal remains possible. A study published Thursday by Climate Analytics suggests global temperatures could peak at 1.7°C before declining, but only if electrification meets two-thirds of energy demand by 2050 as renewables costs continue falling. This electricity, paired with hydrogen, biomass, and synthetic fuels, must fully displace fossil fuels from the energy mix by 2040. Wealthy nations would need to hit net zero even sooner, by 2050, according to the study.

"We've lost precious time in the critical decade for climate action. Yet the past five years have unleashed a revolution in renewables and batteries, smashing global records. Harnessing these tailwinds can help us recover lost ground. The window to limit overshoot is now open. The choice is ours," says Neil Grant, one of the study's authors. Those same five years saw post-pandemic growth incentives combine with resurgent far-right climate denial worldwide, shattering the optimism that launched the Paris decade.

Renewables

Renewables have doubled over the past decade and are on course to triple soon, yet 80% of global energy still comes from fossil fuels –oil (30%), coal (28%) and gas (23%)– per the IEA. This is despite solar and wind delivering the sharpest cost reductions over the last decade and now being the most competitive energy sources. Renewals grow at 6% annually while fossil fuels expand at 1.5%. But fossil fuels shouldn't be growing at all – they need to be cut to zero. "The problem? Relentless energy demand growth means new renewables are added to the total rather than displacing fossils", Alcaraz explains. Without aggressive efficiency gains and circular economy measures to curb consumption, fossil phase-out as science demands remains impossible.

Over the past decade, numerous countries have opened fresh oil and gas fields when science demands the opposite. The US leads, becoming the world's top producer and exporter – boosted by Russia's Ukraine-induced isolation – though CIDOB's Martínez insists it "remains committed to renewables" via Biden's Inflation Reduction Act. "Trump's rhetoric is anti-transition, but investments haven't fully pivoted – though fossil reliance is growing," he notes.

Canada, Norway and Australia have also increased their fossil fuel production instead of reducing it, as have China, Iran, Iraq and Brazil – the latter positioning itself as a climate leader while hosting COP30.

The stumbling block is clearly the immense power of the fossil fuel industry – felt even at UN climate summits and others like the failed plastics treaty or stalled shipping emissions deal. All recent defeats that signal a troubling reversal from the 2015 Paris Agreement momentum.

More than 225 climate NGOs have formally demanded fossil fuel companies be barred from UN climate talks – so far without success. At this year's Amazon COP30, hundreds of oil and gas lobbyists will attend once more, either as country delegates or observers. "The WHO only made progress on tobacco after banning industry lobbyists from talks", notes Anna Pérez, researcher at the Institute for Sustainable Development and International Relations (IDDRI). She highlights that "Edelman – the firm managing COP30 communications – also handles Shell's PR in Brazil".

COP30's core goal is finally implementing the Paris Agreement after a decade defining its rules. "Implementation now happens nationally, but the UN wants to strengthen oversight", Pérez explains. Paris created transparency mechanisms to track countries' NDCs (national climate plans). The Paris Agreement sets no binding targets, leaving it to each country to submit whatever commitments it deems appropriate, "but those commitments become binding once submitted", Alcaraz states. Furthermore, since 2025 the International Court of Justice (ICJ) has ruled – in a landmark advisory opinion – that Paris Agreement compliance is a legal obligation for governments. Warning to governments: penalties may follow non-compliance.