As Arizona ends one of its driest monsoons on record, many may wonder how climate change is affecting the source of one-third to one-half of the state’s rainfall.

A new paper in the journal Nature Geoscience analyzes a Grand Canyon cave formation for clues.

Climate models disagree about the monsoon’s future under warming conditions. Some say it will intensify, but not necessarily bring more precipitation, while others say it will weaken.

To help answer the question, the authors analyzed the water record stored in a stalagmite in a Grand Canyon National Park cave.

Not unlike tree rings, stalagmites retain records of temperature, precipitation and even vegetation as they grow over time. The one used in the study provided a proxy for precipitation and groundwater recharge from 8,500-11,700 years ago, when the region was warmer.

Analysis showed more water filtered into the cave back then, likely because regional warming had brought the monsoon northward as the last ice age ended.

The findings could mean warming will bring more precipitation, but they fall well short of settling the debate.