Instrumental Artefacts Can Reverse Apparent Lightning–Climate Trends

Abstract Lightning is an Essential Climate Variable, yet long‐term detection records may be compromised by changes in detection technology. Using more than three decades of Austrian lightning observations (1992–2024), we show that instrumental artefacts can reverse the apparent sign of lightning–climate trends. While raw records suggest a significant decline in cloud‐to‐ground lightning, a meteorological reanalysis‐driven reconstruction reveals a robust upward trend in cloud‐to‐ground flash occurrence, with the strongest increase over Alpine terrain. Validation demonstrates that changes in detection hardware and software, rather than atmospheric variability, dominate the spurious signal in the uncorrected record. Because many lightning networks worldwide have undergone similar technological transitions, such biases may be widespread and lead to errors in climate research and hazard assessment. The reconstruction requires only a short period of stable reference data and can therefore be transferred to other ground‐based networks and emerging satellite lightning sensors.