Scientists Warn of Record Heat, Threats to Climate Monitoring Systems

Leading scientists have issued a stark warning about accelerating planetary heating and the worsening of critical climate indicators. An annual study, published between major Intergovernmental Panel on Climate Change (IPCC) assessments, reveals record human-induced warming and a surge in marine heatwaves. More than 70 scientists, including IPCC contributors, expressed alarm over the findings.

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These indicators represent an essential monitoring of the vitals of a patient exhibiting ever increasingly troubling symptoms.

Peter Thorne, a physical geography professor and co-author, described the indicators as an "essential monitoring of the vitals of a patient exhibiting ever increasingly troubling symptoms." He emphasized that the global observation capabilities underpinning this monitoring are, for the first time in his lifetime, "systematically either actively degrading or at risk." This degradation poses a significant threat to the world's ability to track and understand global warming.

The study indicates that global temperatures reached approximately 1.39C above preindustrial levels in 2025, with nearly all of this warming attributed to human activities. Scientists predict that human-induced warming will reach the critical 1.5C threshold around 2030. This trajectory puts the world on a path to exceed the goals set by the 2015 Paris climate accord, which aims to limit warming to well below 2C, preferably 1.5C.

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They all rest upon a suite of global observation capabilities which are, for the first time in my lifetime, systematically either actively degrading or at risk.

The report details a significant "Earth's energy imbalance," where the planet is accumulating heat at an unprecedented rate. This imbalance has doubled in recent decades, driven by a combination of record-high greenhouse gas emissions and a reduction in aerosol pollution, which previously had a cooling effect. While emissions are slowing, the "carbon budget" remaining to keep warming below 1.5C is estimated to be exhausted in approximately three years, making the target increasingly unachievable.

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Without human influence, it should be close to zero, but it has been growing since the 1970s and is now at a record high, doubling in recent decades.

Furthermore, sea levels have risen about 23 cm since 1901 and are accelerating, reaching 3.84 mm per year due to melting ice and thermal expansion. The frequency of marine heatwave days has more than tripled since 1991, reaching an average of 65 days in 2025, adding another critical indicator of the planet's deteriorating health.

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Given that greenhouse gas emissions are still on the rise, keeping global warming below this (1.5C) threshold now seems unachievable.