Recently in Antarctica, a penguin with all black feathers was discovered. This trait had never been seen before. What is
the likely source for this "new" trait?

The penguin in question has a rare genetic mutation called melanism, which makes skin, fur, and feathers black due to a high concentration of the pigment melanin. It's basically the opposite of albinism, which is caused by a lack of pigment.

burning of wood and coal

explanation:

the panel also concluded there's a better than 95 percent probability that human-produced greenhouse gases such as carbon dioxide, methane and nitrous oxide have caused much of the observed increase in earth's temperatures over the past 50 years.