A robust method to determine the beginning of a new climate

When does ‘anomalous weather’ become 'a new climate’? The moment that variations in a specific climate variable turn into the new normal is termed Time of Emergence (ToE). Scientists from the University of Groningen and the Royal Netherlands Meteorological Institute (KNMI) have developed a method to predict time of emergence in various Arctic regions, based on warming, wetting, and sea ice melting. The ToE for temperature and sea ice is in the near future, i.e. somewhere before 2050, whereas the amount of rainfall will enter a new climate state at the end of the century. The results have been published in the journal Scientific Reports on 12 April.

The scientists have used 14 global climate models and fed them with various greenhouse gas emission scenarios and aerosol amounts to reconstruct the past and predict future Arctic climate changes. The ToE was defined as the time when the values for a climate variable have been higher than 97.5 percent of the historical values for ten consecutive years. The results show that, even though the Arctic is rapidly warming, ToE for temperature and sea ice cover has generally not yet been reached. This is mainly due to the extremely high natural variability in these Arctic variables.

Most sensitive predictor for climate change

There are large regional differences. For example, sea ice thickness has already reached a new climate state in the central Arctic region, as there is a relatively small variability in year-to-year thickness. This makes sea ice the most sensitive predictor for climate change.

‘We were excited to see that we were able to estimate ToE in a consistent and robust way,’ says Richard Bintanja, University of Groningen Professor of Climate and Environmental Change and corresponding author of the study. The new predictions for ToE will help local Arctic inhabitants to adapt to the new Arctic climate. Bintanja: ‘The next step is to apply these insights in society, policy, and ecology’.

Reference: Nicoleta Tsakali, Marlen Kolbe, Richard Bintanja & Nomikos Skyllas: The time of emergence of Arctic warming, wetting and sea ice melting. Scientific Reports, 12 April 2025