Drier conditions could reduce grass production, and grass was crucial because livestock depended on stored hay during winter. citeturn0search2turn0search5

That distinction matters.

A farmer does not need a thermometer to know that a climate is becoming harder.

If grass grows poorly, hay stores shrink.

If hay stores shrink, fewer animals can survive winter.

If fewer animals survive, households have less milk, meat, wool, breeding stock, and social wealth.

A change in precipitation can therefore produce a crisis even without an obvious plunge in temperature.

Other research has also suggested that changing sea level affected Norse farms.