Compound event metrics detect and explain ten-fold increase of extreme heat over Europe

Weather and climate extremes such as heatwaves are crucial climate hazards to people and ecosystems worldwide. In any region, climate change may alter their characteristics in complex ways so that rigorous and holistic quantification of the extremity of such events remains a challenge, impeding also uses by impact, attribution, and litigation communities. Here we introduce a new class of threshold-exceedance-amount metrics that track changes in event frequency, duration, magnitude, area, and timing aspects like daily exposure and seasonal shift -- separately and up to compound total extremity (TEX). Applying them to extreme heat and showing their utility, at local- to country-scale (example Austria) and across European land regions, we revealed TEX amplifications of ~10 [4 to 25] (Europe 45-55{\deg}N) and ~8 [6 to 20] (Austria) for 2008-2022 vs. 1961-1990, strongly emerged from natural variability and an unequivocal evidence of anthropogenic climate change. Given their fundamental capacity to reliably track any threshold-defined climate hazard at any location, the new metrics enable a myriad of uses, from improving impact quantifications to climate action.