Other researchers said the study authors’ method can’t determine whether the soil moisture changes recorded in the tree ring data occurred because of an increase in greenhouse gases or because of natural causes — which are also included in the model simulations used to create the fingerprint. For instance, there’s evidence that the sun emitted slightly more energy over the first half of the 20th century, which also affected the climate.

Source: Los Angeles Times May 01, 2019 17:06 UTC