Bad news about the state of the planet comes at you in waves, and even the most eco-conscious audience must have a hard time keeping up with the latest threat levels.

An international team of researchers, including two University of Minnesota scientists, is attempting to assess where we are and find us a soft place to land.

In an article to be published Thursday in the journal Nature, they call it a "safe planetary operating space" that they say will lead to a sustainable future. The researchers introduce nine issues that have boundaries or thresholds that humans must respect in order to avoid potentially catastrophic consequences. Much of their analysis is gloomy.

"What is unique is that it is not a bunch of individual pieces but a synthesis," said Jon Foley, co-author and director of the U's Institute on the Environment (full disclosure: where I am an associate fellow). "We realize how close we are to the edge of the cliff, tipping the earth to something unrecognizable to us."

The concept sounds like Malcolm Gladwell's notion of a "tipping point," only in this case the issues are not ideas but ecological problems. The nine are:

Climate change
Stratospheric ozone
Land use change
Freshwater use
Biological diversity
Ocean acidification
Nitrogen and phosphorus inputs to the biosphere and oceans
Aerosol loading
Chemical pollution

The authors claim that tipping points may have been reached in climate change, biodiversity and nitrogen inputs. "Observations of a climate transition include the rapid retreat of summer sea ice in the Arctic Ocean, the melting of almost all mountain glaciers around the world, and an increased rate of sea-level rise in the past 10 to 15 years," said co-author John Schellnhuber, director of the Pottsdam Institute for Climate Impact Research, in a release. And what affects one area could also influence another, the authors note.

Foley said his work shows that the nitrogen pollution is "in excess of anything we've seen in geologic history."

The authors, and there are 28 of them, do not claim that the boundaries are completely exact. It's more like a first attempt at a map with many unexplored regions.

They expect criticism. "We could wait for a few more decimal points before publishing," Foley said. "But we felt the core message was sound and important to hear."

It will be interesting to see what happens to the article, whether it has a chance to be seminal, along the lines of "The Tragedy of the Commons," or if it passes relatively unnoticed. Only time will tell, of course, and in the meantime the experiments and modeling continue.