Global Warming said to be killing species

I read the article, and while I know there are those who disagree on the seriousness of global warming versus the knowledge that the earth's climate has made shifts in the past that can not be blamed on non-natural reasons, after reading this:

At least 70 species of frogs, mostly mountain-dwellers that had nowhere to go to escape the creeping heat, have gone extinct because of climate change, the analysis says. It also reports that between 100 and 200 other cold-dependent animal species, such as penguins and polar bears are in deep trouble.

"We are finally seeing species going extinct," said University of Texas biologist Camille Parmesan, author of the study. "Now we've got the evidence. It's here. It's real. This is not just biologists' intuition. It's what's happening."

Parmesan said she worries most about the cold-adapted species, such as emperor penguins that have dropped from 300 breeding pairs to just nine in the western Antarctic Peninsula, or polar bears, which are dropping in numbers and weight in the Arctic.

I started to wonder, there have been extremely warm periods and extremely cold periods in the past. Some of these species obviously made it thru then else they would have been extinct prior to today's time. Are there other factors that are involved in addition to global warming?

The article also states:

Populations of animals that adapt better to warmth or can move and live farther north are adapting better than other populations in the same species, Parmesan said.

"We are seeing a lot of evolution now," Parmesan said. However, no new gene mutations have shown themselves, not surprising because that could take millions of years, she said.

It appears that the species that can evolve will survive, so while I do believe we can do more to prevent non-natural "pile on" in changing the environment, how much of this is related strictly to global warming rather than the natural process of change with some species dying out? If some of these species survived past shifts in the climate why is that not happening again?