Over the past several days, I have been in central Africa. Along with my colleague Anderson Cooper and Discovery Channel's Jeff Corwin, I have been working on a project called "Planet in Peril." The goal of this particular trip is to investigate climate change. It used to be called global warming, but as with many things, that was a little too simplistic.

In central Africa, I have been traveling through four countries, all of which border Lake Chad. You may ask, as I did, why Lake Chad? After all, isn't there evidence of climate change everywhere? The answer is yes, but Lake Chad, which used to be one of the world's largest lakes, has shrunk to just 10 percent of its size over the last forty years. Many people here in Africa do specifically blame climate change and more specifically greenhouse gases, produced by the industrialized world. But as we are learning, that is only part of the equation.

As I visited fishing villages in Chad, Cameroon, Niger and Nigeria, it seemed just about everyone had an explanation as to why the water had disappeared. Besides climate change, people pointed to the numerous dams built in the 1970s to improve irrigation for farmlands. Those dams greatly restrict the inflow of water from rivers to the lake. Some say local governments have badly misallocated the water supply that previously kept the lake full of water. Some remind us that the population has increased in some of these areas, along with consumption of water. Others place it in the hands of God. But most say it is a combination of all these things.

If you look back even further, as we did, we learned that the lake has shrunk dramatically at least once before. At a time when the term greenhouse gas didn't exist, water levels receded and no one was exactly sure why it happened. Eventually, the water came back. No one was sure why that happened either. "It may just be a long term cycle," the project manager of the Lake Chad Basin Commission told me during an interview. No surprise then that he is confident one day the water will return.

On the days we were shooting this story, it was 113 degrees in the shade. The case for global warming seemed pretty easy to make as I literally watched water evaporate from the lake in front of me. Still, it is worth taking a deeper look at the ebbs and flows of our planet and what is really driving them.

The topic of climate change or global warming tends to invoke strong emotions in people and I am curious what you think. Do you think greenhouse gases and carbon pollution in the United States, or China for that matter, are causing water to disappear in Africa?