Mercurius
Legend
The first age is not our world. The portal stones come from the first age, so the one power was known and used during that period, making it an alternate reality of ours. That means that the landscape doesn't have to be identical. Nor does there even have to be climate change.
This is debatable. The first age--or rather, the age before the Age of Legends, may or may not be our current age which, I'll remind you, is not over.
I decided to re-read Eye of the World and came across a few tidbits from Thom Merrillin in the early chapter, "The Gleeman," in which he mentions various personages from our era such as "Mosk the Giant" (Moscow) and "Materese the Healer" (Mother Theresa). They're summarized on this page about real-world references. I had to chuckle at "Anla the Wise Counselor" (Ann Landers).
Thom says, "Old stories, those...Stories from the Age before the Age of Legends, some say. Perhaps even older."
Meaning, all we know is that they are from before the Age of Legends, but it isn't clear to Thom--and thus perhaps to Robert Jordan himself--whether the first age is our age, or whether our age is from an earlier cycle of seven ages.
But what is clear is that it is our world, and in our future. That said, Jordan seems to emphasize the cyclical nature of time, so that past and future are not strictly linear. This is resonates with the Hindu view of time (the yugas, etc), and other variations on Eternal Return, from Eliade's study of myth to Nietszche's rather scary view of Eternal Recurrence, that we live the same life, over and over again.
Jordan says the same basic seven ages are repeated, but while the underlying patterns and nature of each age are the same, the details are different.