By Magdalena Scharf
Berlin – Melting ice caps, raging wildfires, billowing smokestacks — these are the familiar visuals of climate change. But heat? Heat is invisible. And that presents a fundamental challenge for journalists: How do you illustrate something you can’t see?
Yet heat is one of the most immediate — and deadliest — consequences of global warming. According to the World Health Organization (WHO), extreme heat claims an estimated 490,000 lives worldwide every year. And it’s getting worse: the WHO predicts a 50% increase in heat-related deaths by 2050.
But when does hot weather officially become a heatwave?
In Germany, the Federal Ministry of Health defines a heatwave as several consecutive days of unusually high temperatures. The German Weather Service (DWD) gets specific: temperatures must exceed 28 °C for at least three days in a row.
Definitions vary around the world — and even within countries. In Italy, for example, the threshold depends on the region. According to the European Centre for Medium-Range Weather Forecasts (ECMWF), a heatwave in Calabria requires temperatures of 39.5 °C in August and September. In Bologna, it’s “only” 36.5 °C. (Heat waves and cold spells in Europe derived from climate projections documentation – Copernicus Knowledge Base – ECMWF Confluence Wiki)
Can we see heatwaves coming?
Researchers at the Max Planck Institute for Meteorology (MPI-M) believe so. They’ve found that extreme European heatwaves are often preceded by warming in the North Atlantic Ocean. According to MPI researcher Lara Wallberg, this heat accumulation can be detected up to three years in advance.
As the dangers of extreme heat become harder to ignore, some cities are responding with a new role: the Chief Heat Officer. Cities like Athens and Los Angeles were among the first to appoint officials dedicated to tackling the urban heat island effect.
“I love our city spaces — they are the heartbeats of communities and families. And yet we’re on the brink of losing them to rising heat,” says Eleni Myrivili, the UN’s Global Chief Heat Officer. “It’s not just about preserving our cities; it’s about preserving the essence of our shared humanity.”
Eleni Myrivili’s passionate pursuit: A Chief Heat Officer on a mission | UN Habitat
Image: Gerd Altmann, Pixabay