What was the weather like on the day you were born?

 

It's not a hypothetical question anymore.

Thanks to a new tool released this month by the Copernicus ECMWF Climate Change Service, you can find out — hour by hour, anywhere on Earth, going back to January 1940.

It's called Weather Replay.

And it is genuinely extraordinary.

The app is a time machine for the atmosphere.

Select any date from the past 85 years, click any point on the globe, and within seconds you can watch the weather of that moment unfold: temperature, wind, pressure, precipitation, gusts, jet streams.

The full 48-hour evolution.

All powered by the ERA5 reanalysis dataset and ECMWF's meteorological archive.

Why this matters beyond the "wow" factor:

• Reanalysis is one of the most useful products in modern climate science.
• It blends decades of observations with state-of-the-art atmospheric models to reconstruct a physically consistent record of every hour of weather, everywhere.
• Until tools like Weather Replay, that record lived mostly inside research institutions.
• Now it is open, intuitive, and accessible to anyone — students, journalists, communicators, citizens, decision-makers.

A quiet, beautiful demonstration of why investment in the global observation and reanalysis enterprise pays off across science, policy, and public understanding.

Image of the week : a very rare phenomenon with a spectacular optical illusion of boats floating above the sea

 

The photo was taken -Saturday morning this month in Sitges, a coastal town in Catalonia, Spain. 

Xavier Salmerón

Fata morgana