Climate change could be shifting the limits of weather predictability and pushing reliable 10-day forecasts out of reach, report researchers.

The limit of reliable temperature, wind, and rainfall forecasts falls by about a day when the atmosphere warms by even a few degrees Celsius.

“Our results show the state of the climate in general has implications for how many days out you can say something that’s accurate about the weather,” says atmospheric scientist Aditi Sheshadri of Stanford University, lead author of the study in Geophysical Research Letters. “Cooler climates seem to be inherently more predictable.”

Widespread changes in weather patterns and increased frequency and severity of extreme weather events are well documented consequences of global climate change. These departures from old norms can bring storms, droughts, heatwaves, and wildfire conditions beyond what infrastructure has been designed to withstand or what people have come to expect.

Yet numerical weather models are still generally able to predict day-to-day weather 3 to 10 days out more reliably than they could in decades past, thanks to faster computers, better models of physical atmospheric processes, and more precise measurements.

The new research, based on computer simulations of a simplified Earth system and a comprehensive global climate model, suggests the window for accurate forecasts in the midlatitudes is several hours shorter with every degree (Celsius) of warming. This could translate to less time to prepare and mobilize for big storms in balmy winters than in frigid ones.

For precipitation, predictability falls by about a day with every 3 C rise in temperature. The effect is more muted for wind and temperature, with one day of predictability lost with each 5 C increase in temperature.

While global average temperatures have increased by 1.1 C (2 F) since the late 1800s, not all places are warming at the same rate. Some US cities have seen average annual temperatures rise by well over 2 C since 1970. Seasonal variations can be even more extreme.

Further analysis will be needed to assess whether winter weather is inherently more predictable than summer weather, Sheshadri says, but the new results strongly indicate a shorter time horizon for reliable weather predictions in places that warm beyond their historical norms.

Read the full article about climate change impacts forecasts by Josie Garthwaite at Futurity.