Some scientists say CO2 levels put the world in a new geological epoch: human-caused Anthropocene

As carbon dioxide in the atmosphere hits a level not seen in millions of years, a new climate-change report says the world could lose many of its plants and animals by 2080.

Carbon dioxide levels near the summit of the Mauna Loa volcano in Hawaii were recorded at more than 400 parts per million for the first time since measurements began 55 years ago, and those levels are thought to be the highest since the Pilocene Epoch, between 2.6 to 5.3 million years ago. The rise could be putting us in what some scientists dub the Anthropocene because they agree that increases in ambient temperatures and changes in related processes are directly linked to rising anthropogenic, or human-caused, greenhouse-gas concentrations in the atmosphere.

Robert Kunzig writes for National Geographic News, "Many scientists argue that the CO2 concentration must be stabilized at 450 ppm to avoid the worst impacts of climate change," while some activists argue for a goal of 350 ppm. (Read more)

The American pika is one of many animals that can't
tolerate increased heat brought on by climate change,
scientists say. (U.S. Geological Survey photo via AP)

While most studies that look at the affects of climate change on plants and animals look at rare species, a study released in the journal Nature Climate Change looked at 50,000 common species of plants and animals, finding that more than 50 percent of the plants and 33 percent of the animals "could lose about 50 percent of their range by 2080 if the world continues its current course of rising greenhouse gas emissions," reports Neela Banerjee for the Los Angeles Times. (Read more)