CNN

The dwindling water supply at Lake Chad, Chad

"The white man will brings us water. Only, the white man has power."

I sat there stunned as I listened to the words of 45-year-old Maloum Mahamat. He's the chief of a tiny fishing village on the shores of what is left of Lake Chad in Central Africa. Mahamat is possibly the last in a long line of generations of fishermen. I press him on what can be done to help his people adapt to the receding water. He has two answers. The white man will come fix it and God will do what he must. In the 10 days our team spent following the shorelines of what's left of Lake Chad, we heard those two responses time and time again.

Whether it's on television or words, the story of Lake Chad is tough to tell. In the 1960s, Lake Chad was one of the world's largest lakes. At its greatest levels in modern history, it was as if the entire state of Vermont was covered in water -- simply enormous. Today, Lake Chad is one-tenth of its former size. Yes, it's shrunk by 90 percent in the last 40 years. The lake has always been shallow. Even at its deepest, it never measured more than 30 feet deep. Now its greatest depths measure only 3 feet to 6 feet.

The waters are receding and are becoming shallower. There are fewer fish in species, number and size. Fishermen need to adapt and find new ways to make a living. Less water means less vegetation. Less vegetation creates more sand dunes. Sand dunes lead to even less precipitation. It's an interconnected cycle. Tragically, as populations increase and resources become scarce, more people rely on the lake for sustenance than ever before, even as it has less and less to offer.

So, why is all this happening? The United Nations Environment Programme says that about half of the lake's decrease is attributable to human water use such as inefficient damming and irrigation methods. The other half of the shrinkage is due to shifting climate patterns. Anada Tiega of the Lake Chad Basin Commission blames climate change for 50 to 75 percent of the water's disappearance.

Dr. Sanjay Gupta and I, along with our crew, traveled to Africa to find out just how much of the lake's disappearance was due to climate change and global warming. It's definitely hard to discern.

The truth is that Lake Chad has waxed and waned before. According to the U.S. Geological Survey, the lake has probably dried out about a half-dozen times in the last 1,000 years. Scientists are confident that Lake Chad's waters will one day return, but that day probably will not be in this lifetime.

What effect do you think climate change has had on Lake Chad, if any? If Lake Chad naturally disappears and returns over geological time, does it matter what we do in the present. Do you believe in or care about climate change whether the effects are felt in Africa or elsewhere? Do you want to learn more about climate change, global warming and human health?

Dr. Sanjay Gupta reports from Lake Chad on climate change and the shrinking resources of the desert, tonight on "Anderson Cooper 360," 10 p.m. ET