Why 'haze' and 'trash' are becoming earth's new seasons

Climate change and pollution are playing havoc with our longstanding understanding of seasonal patterns.

- Felicia Liu and Thomas Smith

Throughout history, people have viewed seasons as relatively stable, recurrent blocks of time that neatly align farming, cultural celebrations and routines with nature's cycles. But the seasons as we know them are changing.

Human activity is rapidly transforming the earth, and once-reliable seasonal patterns are becoming unfamiliar.

In our recent study, we argue that new seasons are surfacing. These emergent seasons are entirely novel and anthropogenic (in other words, made by humans).

Examples include "haze seasons" in the northern and equatorial nations of South-east Asia, when the sky is filled with smoke for several weeks. This is caused by widespread burning of vegetation to clear forests and make way for agriculture during particularly dry times of the year.

Or there is the annual "trash season", during which tidal patterns bring plastic to the shores of Bali, Indonesia, between November and March.

At the same time, some seasons are disappearing altogether, with profound consequences for ecosystems and cultures.

These extinct seasons can encompass drastically altered or terminated migratory animal behaviour, such as the decline of seabird breeding seasons in northern England.

Climate change is also calling time on traditional winter sport seasons by making snow scarcer in alpine regions.