The time of emergence of Arctic warming, wetting and sea ice melting.

In the rapidly warming and wetting Arctic, the time of emergence (ToE) of a new climate state occurs when trends of climate indicators are large enough to surpass the strong natural climate fluctuations in the Arctic. Thus far, uncertainties in climate model projections, variability and methods have yielded diverging estimates of Arctic ToE. Here we use a robust method and future projections of multiple state-of-the-art climate models to show that, generally, sea ice thickness (2036-2051) and surface air temperature (2033-2050) emerge first, followed by sea ice cover (2039-2074), and precipitation/rainfall (after 2077). Autumn generally exhibits the earliest ToE-values due to rapid sea ice retreat. The earliest ToE for temperature and sea ice thickness occurs in the Central Arctic, whereas sea ice cover and rainfall first emerge in the Barents Sea region. Most regions of the Arctic are close to a new climate state (for temperature and sea ice), with wide-ranging and possibly irreversible consequences for vulnerable Arctic ecosystems and human activities.