Science Source

Attributing the US Southwest's recent shift into drier conditions

States that the US Southwest has been getting drier and warmer over the last few decades
States that these changes fit the common narrative of what might be expected to happen in response to increasing greenhouse gas concentrations
States that natural variability of precipitation and temperature is known to be large in this region, making it difficult to clearly attribute the recent drying and warming to greenhouse gas forcing
Shows that while the warming is largely due to greenhouse gas forcing, the drying is mostly due to internal climate variability
Finds that only an insignificant drying remains after accounting for this internal climate variability
Notes that unlike previous studies that relied exclusively on climate models, this study bases its conclusions on a combination of observations, an empirical statistical method, and climate models