Much has been publicised about the possible apocalyptic effects of global warming on Earth: melting polar ice caps leading to massive flooding that wipes out continents, food shortages and extreme hunger due to droughts, and powerful storms that batter and destroy country after country.

It turns out this is not the worst-case scenario yet. A study published last week, coinciding with talks in Paris on ways to address global climate change, revealed a scarier scenario caused by global warming: the lowering of levels of oxygen in the Earth's atmosphere, causing widespread deaths among animals and human beings.

This conclusion was reached by a team of researchers led by Applied Mathematics Professor Sergei Petrovskii from the University of Leicester after studying and making a computer model of oxygen production by phytoplanktons, or microscopic sea plants that produce about two-thirds of the oxygen that humans breathe in.

"Global warming has been a focus of attention of science and politics for about two decades now," Petrovskii explained, as quoted by Thinkpol.com.

"A lot has been said about its expected disastrous consequences; perhaps the most notorious is the global flooding that may result from melting of Antarctic ice if the warming exceeds a few degrees compared to the pre-industrial level. However, it now appears that this is probably not the biggest danger that the warming can cause to humanity," he said.

According to the research published on the peer-reviewed journal Bulletin of Mathematical Biology, phytoplankton's ability to produce oxygen would be impaired if average global warming reaches 6 degrees Celsius.

This scenario will "obviously kill most of life on Earth," the research team said in their study.

"About two-thirds of the planet's total atmospheric oxygen is produced by ocean phytoplankton – and therefore cessation would result in the depletion of atmospheric oxygen on a global scale," Petrovskii said.

"This would likely result in the mass mortality of animals and humans," he warned.

The International Energy Agency has already earlier warned that six-degrees-Celsius rise in global temperature is possible if unbridled carbon emissions continue.

Climate negotiators in Paris are trying to reach consensus on limiting global warming to 2 degrees Celsius.