Six of nine key planetary ‘health boundaries’ have been crossed, said researchers in a new report.

In categories such as climate change, biosphere integrity, land system change and freshwater change, humans have entered a world that is increasingly inhospitable, the scientists said in a recent report in the Science Advances journal.

The global team of dozens of experts found that the planet is "well outside the safe operating space for humanity" – because of human activity.

The nine categories govern the stability and health of the planet.

The only three markers that are considered healthy are stratospheric ozone depletion, atmospheric aerosol loading and ocean acidification. But the pressure on these categories is increasing.

The study builds on a 2015 assessment, and it found that eight of the nine categories have worsened. Only ozone depletion has improved. The 2015 report said that only four of the nine boundaries had been breached.

"We don't know that we can thrive under major, dramatic alterations of our conditions," said co-author Katherine Richardson, of the University of Copenhagen, at a news conference.

“This does not mean that we are pushing the planet across an irreversible collapse,” added Johan Rockström, director of the Potsdam Institute for Climate Impact Research and co-author of the study. “But it means we’re losing resilience – we are putting the stability of the Earth system at risk, and the buffering capacity of the Earth system to buffer stress and shocks at risk.”

He told CNN: “We are approaching tipping point.” He continued: “We are coming close – it is what you would call a code red.”

The key, he said, is not just the climate. “It is also the living biosphere such as the fresh water and the overloading of nitrogen and phosphorous and air pollutants, which is undermining what we call the strength or resilience of the planet and its ability to deal with shocks and stresses,” he told CNN in an interview.

“So we have a climate crisis and a weak planet,” he said. “We need really, really rapid action.”

He said: “There are two direct impacts if you think of our long-term future, as humanity on Earth.

“We’ve understood we are in climate crisis, but what this study shows is that even if we would phase out coal, oil and gas, and become more or less fossil-fuel free, we would still have problems with climate because we’ve breached the boundaries on land and biodiversity, and water and nitrogen and phosphorous, and as they will hit us back. 50% of GHG emissions from fossil fuel burning are in the living biosphere.”

“So we need a strong planet to deal with the climate crisis,” he said.

He also said that breaching these boundaries threatens food security, water security and social stability. “These are security matters that fundamentally determine the stability of society, and therefore issues of conflict, migration and displacement,” he concluded.

At the press conference, Richardson warned: “We can think of Earth as a human body, and the planetary boundaries as blood pressure. Over 120/80 does not indicate a certain heart attack but it does raise the risk."

The concentration of carbon dioxide in the atmosphere – CO2 is the main greenhouse gas (GHG) – has risen to around 417 parts per million (ppm), which is much higher than the level that is considered safe, of 350 ppm, said the scientists.

Species extinction is also careening out of control. The average rate is estimated to be 10 or more times faster than the average rate over the past 10mn years, reported Reuters.

Rockström said the study’s fundings should be seen as an alert. "In my career I've never been sitting on so much evidence as today and can be so clear in our communication," he said, citing last week’s disappointing United Nations Global Stocktake report.

"It is a complete failure ... and it's a large risk ... We're still following a pathway that takes us unequivocally to disaster."

According to the stocktake, the UN says there is only two years left to reduce emissions and stay within the 1.5C temperature increases that were the target for the Paris accords, but time has almost run out and if radical action is not taken now the target will be missed.

UN Secretary General António Guterres had said earlier in September: “Our planet has just endured a season of simmering – the hottest summer on record. Climate breakdown has begun.”