By Colin Barras

An extraordinary chapter has just been added to the story of the First Americans. Finds at a site in California suggest that the New World might have first been reached at least 130,000 years ago – more than 100,000 years earlier than conventionally thought.

If the evidence stacks up, the earliest people to reach the Americas may have been Neanderthals or Denisovans rather than modern humans. Researchers may have to come to terms with the fact that they have barely scratched the surface of the North American archaeological record.

“We often hear statements in the media that a new study changes everything we knew,” says Chris Stringer at the Natural History Museum in London. “If this result stands up to scrutiny, it does indeed change everything we thought we knew about the earliest human occupation of the Americas

A tipping point is a critical threshold at which a dynamical system undergoes an irreversible transformation, typically owing to a small change in inputs or parameters. This concept is very broad and can refer to the extinction of an animal or a plant species, the depletion of a water source, or the financial collapse of an institution, among many other natural and social phenomena.
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"But what our study showed, and this is its main contribution, is that for certain cyclical phenomena, the dynamics of the system last for a certain time after the tipping point, and this persistence may mask the transition itself," Medeiros said. "Take an endangered species, for example. It may have passed the point of no return and become irreversibly doomed. Nevertheless, individual members of the species continue to exist and reproduce in the wild. This transient effect conceals the fact that in the long run, the species is already extinct. In our study, through numerical simulation, we succeeded in observing this transient effect following the singularity that configures a tipping point."
Thus, the fundamentals of a phenomenon change irreversibly at the tipping point, but owing to a kind of "residual effect" the process appears to retain its original characteristics for a time, masking the transformation that has occurred.

Read more at: https://phys.org/news/2017-05-collapse-natural-social.html#jCp

The Arctic is warming more than twice as fast as the rest of the planet, suggests a huge assessment of the region. The warming is hastening the melting of Arctic ice and boosting sea-level rise.
The report, compiled by more than 90 scientists, documents the myriad changes already under way across the Arctic because of climate change—from declining sea ice and melting glaciers to shifting ecosystems and weather patterns. From 2011 to 2015, the assessment finds, the Arctic was warmer than at any time since records began around 1900 (see 'Arctic warming').
Sea ice continues to decline, and the extent of snow cover across the Arctic regions of North America and Eurasia each June has halved as compared to observations before 2000.
The findings come from the Snow, Water, Ice, and Permafrost in the Arctic report, a comprehensive assessment compiled every few years by the Arctic Monitoring and Assessment Programme, the scientific body that reports to the governments that make up the Arctic Council, a forum for issues affecting the region. The last assessment came out in 2011.

We've all read the reports, or seen the media discussion. Except it can be a little hard to grasp the sheer magnitude of what our species has accomplished. Dire warnings that we've crossed 400 parts-per-million of atmospheric CO2 (a level last seen tens of millions of years ago) may sound pretty bad, but it takes a little intellectual imagination to really grasp what's going on.
Let's give that a shot.

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Except that is for an average output, spread across 263 years. Estimates of today's CO2 production go as high as about 40 billion tons per year. That'd take something like ten billion acres of forest burning each year, which is about 42 million square kilometers. The entire continent of Africa is a mere 30 million square kilometers. So this, plus another third, on fire, each year: