This sylvan mini-hospital is on lab property just down the road from Bandelier National Monument near Los Alamos, whose residents abandoned their cliff dwellings during a megadrought in the 13th century. The region endured a second major drought in the 16th century.

In those droughts, Dr. McDowell said, forests died but conditions eventually rebounded. Temperatures and precipitation returned to normal ranges.

This time, he said, the rise in temperature is not expected to slow or rebound because it is caused by human activity. It is happening faster than at any time in the geologic record.

What’s new, Dr. McDowell and other scientists say, is that this warmer air acts like a gigantic sponge or wick. So even if rain and snow levels remain the same, the atmosphere will inexorably pull that moisture away from the soil and trees.

Like a hospital I.C.U., the experimental site is noisy. Machines click and roar as they pump warm air into 12 of the chambers, replicating the seven-degree rise in temperature predicted to occur in coming years. Seven of these chambers are also water-deprived. Five chambers serve as controls, with no added stressors. The remaining trees are being monitored outside the chambers, with and without ambient water.

Each tree is hooked up to a variety of sensors, probes and lines that monitor vital signs. Some measurements are taken every 10 minutes, others once a month.

To monitor how trees might succumb to thirst, researchers are measuring water flow inside each trunk. Normally ropes of water molecules are pulled up from the soil and roots by the atmosphere, moving through very small channels called xylem. When the air is warm, it exerts a greater pull on the water, increasing tension. If the tension gets high, the rope breaks and air is introduced. Like an embolism that can kill a person, air bubbles can block the flow of water. A tree can dry out and die.