Sentence:  Phoenix and Lubbock are both caught in severe drought, and it is going to get much worse. We may see many such [dust] storms in the decades ahead, along with species extinctions, radical disturbance of ecosystems, and intensified social conflict over land and water. Welcome to the Anthropocene, the <WSD>epoch</WSD> when humans have become a major geological and climatic force. 
Meaning of the word marked with <WSD> tags:  A particular period of history, "especially" one considered noteworthy or remarkable.