The past couple of weeks have brought troubling climate news.

An article published in the journal Nature said that climate change is reaching a tipping point, reports the San Francisco Chronicle. If that point is reached, it'll mean rapid and irreversible damage to the global environment.

The report joins scores of others highlighting the effect of human activity on climate change.

And last week, the Associated Press reported that atmospheric carbon dioxide concentrations in the arctic have hit 400 parts per million. That hasn't happened in at least 800,000 years, scientists told the AP. Globally, atmospheric concentrations of carbon dioxide are at 395 ppm, though scientists expect that level to surpass 400 ppm within a few years.

Scientists consider 350 ppm to be the highest safe level of atmospheric carbon dioxide concentrations