The year 2023 has etched itself into the annals of history as a scorching testament to humanity’s struggle with a climate crisis largely of its own making, caution senior scientists.

As December waned, swathes of the globe continued to swelter under historically high temperatures, prompting James Hansen, a former NASA scientist renowned for his pioneering testimony on global heating in 1988, to declare that this year would be remembered for its glaring failures.

“When our children and grandchildren look back at the history of human-made climate change, this year and next will be seen as the turning point at which the futility of governments in dealing with climate change was finally exposed,” he said.

“Not only did governments fail to stem global warming, the rate of global warming actually accelerated.”

Following what was likely the hottest July in 120,000 years, Hansen, now directing the climate program at Columbia University’s Earth Institute in New York, forewarned of an ominous trajectory towards a “new climate frontier,” where temperatures surpass any seen in the past million years.

“The bright side of this clear dichotomy is that young people may realise that they must take charge of their future. The turbulent status of today’s politics may provide opportunity,” he said.

Hansen’s sentiments echo a prevailing sense of disillusionment among experts, grappling with the stark disparity between scientific alarm bells and political inertia. It has taken nearly three decades for world leaders to acknowledge the culpability of fossil fuels in driving the climate crisis. Yet, the denouement of this year’s United Nations Cop28 summit in Dubai culminated in a feeble and nebulous call for a gradual “transition away” from fossil fuels, even as evidence mounts of the world hurtling towards perilous temperature extremes.

As scientists grapple with the aftermath of this blistering year, recent data underscores the inexorable march towards record-breaking temperatures. The Japanese Meteorological Agency, the latest to sound the alarm, reported temperatures in 2023 soaring 0.53°C above the global average between 1991 and 2020—a substantial leap from the previous record set in 2016, when temperatures soared 0.35°C above the same benchmark. In the broader context, the world now languishes approximately 1.2°C hotter than preindustrial levels.

The US National Oceanic and Atmospheric Administration concurred, citing 2023 as the hottest year in its 174-year dataset. This verdict followed a relentless onslaught of record warmth, including an unprecedented string of six consecutive months of record-high temperatures, punctuated by the northern hemisphere’s sweltering summer and autumn.

Driven by human-induced global heating and exacerbated by El Niño phenomena, the relentless heatwave showed no signs of abating. In November, the anomaly reached unprecedented levels, with two days registering temperatures exceeding 2°C above the preindustrial average, according to Europe’s Copernicus Climate Change Service. Both Copernicus and the World Meteorological Organization corroborated the year’s record-breaking status, as December witnessed sweltering temperatures across many regions, culminating in the hottest Christmas on record.

Even as the new year dawned, temperature records continued to tumble across central Asia, South America, Europe, and Australia, setting the stage for an unprecedentedly scorching January. While climate trends typically hinge on decadal measurements, many scientists warn that the world is hurtling towards an overshoot of the most ambitious targets outlined in the Paris Agreement.

Veteran climate watchers have been horrified at the pace of change. “The climate year 2023 is nothing but shocking, in terms of the strength of climate occurrences, from heatwaves, droughts, floods and fires, to rate of ice melt and temperature anomalies particularly in the ocean,” Prof Johan Rockström, the joint director of the Potsdam Institute for Climate Impact Research in Germany, said.

He said these new developments indicated the Earth was in uncharted territory. “What we mean by this is that we may be seeing a shift in Earth’s response to 250 years of escalated human pressures … to a situation of ‘payback’ where Earth starts sending invoices back to the thin layer on Earth where humans live, in the form of off the charts extremes.”

Rockström, co-author of the seminal “Hothouse Earth” paper in 2018, expressed profound alarm at the rapid pace of change. He cited a sharp uptick in sea surface temperatures in 2023, an abrupt surge even for an El Niño year, as particularly disconcerting.

“We do not understand why the ocean heat increase is so dramatic, and we do not know what the consequences are in the future,” he said. “Are we seeing the first signs of a state shift? Or is it [a] freak outlier?”

The Antarctic, too, bore witness to unsettling developments, as evidenced by the lowest extent of sea ice recorded by the new Brazilian scientific module Criosfera 2.

“This environmental alert is a sign of ongoing global environmental changes and poses a daunting challenge for polar scientists to explain,” said Francisco Eliseu Aquino, a professor of climatology and oceanography at the Federal University of Rio Grande do Sul and the deputy director of Brazil’s polar and climatic centre.

Throughout the year, West Antarctica grappled with recurrent winter heatwaves, precipitated by atmospheric rivers, while anomalous rainfall events in July defied conventional meteorological expectations. The region’s vulnerability was laid bare once more in January, as a massive iceberg measuring approximately 1,500 square kilometres broke off from the Brunt ice shelf in the Weddell Sea—marking the third such colossal calving event in as many years.

Human influence, chiefly through the combustion of fossil fuels, has engendered a harrowing interplay between polar and tropical dynamics, accentuated by extreme weather phenomena. The collision of cold, wet fronts from Antarctica with record heat and drought in the Amazon has spawned unprecedented storms, exemplified by deadly floods ravaging southern Brazil.

Aquino said this “record record” was a taste of what was to come as the world entered dangerous levels of warming. “From this year onwards, we will understand concretely what it means to flirt with 1.5C [of heating] in the global average temperature and new records for disasters,” he said.

Libya bore witness to its deadliest climate disaster, as a catastrophic flood claimed over 11,300 lives in the coastal city of Derna—a calamity exacerbated by human-induced climate change. Meanwhile, forest fires ravaged vast swathes of Canada and Europe, culminating in the deadliest wildfire in recent US history, which engulfed Lahaina on Maui island.

For those inclined to quantify catastrophe in economic terms, the US endured a record-breaking onslaught of billion-dollar disasters by August, underscoring the staggering toll exacted by climate-induced calamities. Across South America, the reverberations of 2023’s scorching heat reverberated in the form of unprecedented water stress in Uruguay, rampant wildfires in Chile, and the Amazon basin’s most severe drought in half a century.

Raul Cordero, a distinguished climate professor, forewarns that the reverberations of this year’s heatwave will reverberate across the continent, precipitating protracted water shortages, exacerbated wildfires, and heightened economic strains. As El Niño’s waning influence portends continued above-average temperatures, the spectre of further climatic upheaval looms large on the horizon.

As humanity grapples with the fallout of 2023’s searing anomalies, the harbingers of radical and rapid change grow increasingly urgent. Absent transformative action, failure will become the indelible markers of a climate system.