UNEP: why the opportunity to stay below 1.5°C without overshoot is now lost

A report published this Wednesday indicates that the temporary overshoot of the 1.5 °C threshold for global average temperature increase is now inevitable. According to UNEP, decades of insufficient climate action have already consumed the margin of maneuver that would have allowed staying below this threshold without resorting to an ‘overshoot’—that is, an exceedance followed by a return below.

Details of the announcement: who, what, precise figures

UNEP (United Nations Environment Programme) has published an analysis combining the latest climate model projections, including those from ECMWF and Copernicus, with global emissions inventories. The text emphasizes that, even applying the most ambitious current pledges, simulations based on neural networks and predictive models show an overshoot of at least 0.2 °C before 2035. No exact figure is provided on the duration of the overshoot, but the report states that ‘a temporary breach of the 1.5 °C threshold is now inevitable.’ The warning is therefore clear: current pledges will not suffice to avoid crossing above the warming level set by the Paris Agreement.

The statement also indicates that the most optimistic scenarios, which assume rapid CO₂ emissions reductions through massive electrification and carbon capture, remain largely insufficient. Climate models, enriched with satellite data and time series, show that emissions trajectories must be revised downward by several tens of percent for the 1.5 °C window not to be breached, even transiently.

Context: climate objectives at stake, current situation

The Paris Agreement, signed in 2015, aims to limit global warming to 1.5 °C above pre-industrial levels, while pursuing efforts to stay below 2 °C. This ambition rests on the implementation of nationally determined contributions (NDCs) which, combined, must lead to an emissions trajectory compatible with these thresholds. However, annual IPCC reviews and UNEP tracking reports show that cumulative pledges to date amount to only about 55 % of the reduction needed by 2030.

Atmospheric data collected by Copernicus satellites, combined with ECMWF analyses, reveal a continuous increase in CO₂ concentrations, exceeding 420 ppm—a level not seen in over three million years. This rise fuels a radiative imbalance that translates into global warming, already measured at +1.1 °C since the pre-industrial era. Climate models, which now incorporate machine learning algorithms to refine their projections, confirm that the current trend makes overshoot of the 1.5 °C threshold very likely, even if future policies are ambitious.

Furthermore, forecast uncertainties remain significant, particularly regarding climate feedbacks (such as permafrost thaw and methane release). Nevertheless, the convergence of different modeling approaches (statistical, physical, AI) strengthens the credibility of the finding: the ‘window of opportunity’ to avoid any overshoot has already closed.

The stakes: concrete consequences for the climate and populations