Searching for ice age aliens

Could an alien astronomer have detected life on Earth during an ice age? Recent work has calculated how past climate extremes affected the light reflected from vegetation out into space. The results could give hope to our own search for life on distant worlds.From far away, our planet is a single faint speck of light in the sky. Although we have sent radio messages out to potential extraterrestrial listeners, none of these signals have traveled more than a few tens of light years. "