Humans Are Pushing Earth Toward Precipice, Researchers Say

NOAA Tipping Point


Humans may be rapidly and irreversibly pushing Earth into a new geologic age, according to a paper published in the June 7 issue of Nature.

The new age or epoch, called Anthropocene, may begin within decades to centuries or may already be here, researchers said in the paper, Approaching a State Shift in Earth’s Biosphere.

Instead of projecting recent trends into the future or using models to predict the potential impacts of climate change, scientists looked at past “critical transitions,” such as the extinction of dinosaurs 65 million years ago, and determined that humans are now “forcing another such transition.”

Ice Age Compared to Today’s Age

Interestingly, population growth and climate change, which marked the end of the last Ice Age 11,000 years ago, are the forces driving the planet to a tipping point today, according to the paper.

However, there’s a big difference. The rise of nomadic and farming cultures and a warmer climate 11,000 years ago were likely separate events. Today's conditions are "very different" the authors note, with humans being directly responsible for climate change by increasing in numbers; consuming more resources, in particular fossil fuels; and transforming land to agricultural and urban landscapes.

Another reason to compare the end of the Ice Age and today? While it still took thousands of years for glaciers to melt, the period represents one of the fastest transitions, compared to other shifts on Earth that took millions of years.

Researchers say the magnitude of population growth and climate change today far exceed those marking the end of the Ice Age, making the comparison potentially relevant.

For example:

• Population growth, which is now roughly 77 million people per year, is three orders of magnitude higher than the average yearly growth of 67,000 per year that occurred between 400 and 10,000 years ago. If fertility rates remain at 2005-2010 levels, the world’s population could reach 27 billion by 2100. We’re now nearing 7 billion.

• Agricultural and urban landscapes now make up about 43 percent of the Earth, with much of the remaining landscapes lined with roads. About 30 percent of the Earth’s surface was covered with glaciers during the Ice Age.

No Sign of Decrease

Today’s rapid climate change shows no signs of slowing, and the magnitudes of local and global forces causing change today are much greater than those that characterized the end of the Ice Age, according to the paper.

All these dire predictions come with caveats. For example, numerous local changes may trigger a global shift or vice versa, the population rate may increase at a slower rate, ecosystems are complex and may not react in predictable ways, etc.

However, the paper concludes “a future planetary state shift is highly plausible, even though considerable uncertainty remains about whether it is inevitable, and if so how far in the future it may be.”

To minimize adverse impacts, the paper said biological forecasting needs to be improved, root causes of human-driving global warming addressed, and biodiversity and ecosystems better managed.

The paper warns that if critical thresholds on the global scale are reached, widespread social unrest, economic instability, and loss of human life are to be expected. 

The study was compiled by 22 scientists and researchers from a variety of institutions, including universities in the United States, Chile, Spain, and Canada.