The current Southwestern North American megadrought, which began in 2000 and is the most severe in at least 1,200 years, has had significant effects on Earth's upper atmosphere.

1. Cooling of the stratosphere:

- Decreased water vapor in the stratosphere leads to reduced absorption of solar radiation, causing a cooling effect.

2. Changes in atmospheric circulation:

- The drought affects the large-scale circulation in the atmosphere, including the jet stream, which can alter weather patterns globally.

3. Stratospheric ozone depletion:

- Reduced water vapor leads to less hydroxyl (OH) molecules, which are involved in ozone destruction cycles. This can result in increased ozone levels in the stratosphere.

4. Impact on atmospheric chemistry:

- Changes in atmospheric circulation can influence the distribution and transport of trace gases, aerosols, and pollutants, which can have various impacts on air quality and climate.

5. Teleconnections:

- The megadrought can influence climate patterns in distant regions through teleconnection mechanisms, such as changes in the Pacific Decadal Oscillation and the North Atlantic Oscillation, affecting global weather and climate.

The full scope and long-term impacts of the megadrought on Earth's upper atmosphere are still being studied and require ongoing research and monitoring.