Despite the fact that some scientists claim global warming is occuring due to natural causes, the Nobel Prize winner who discovered the hole in the ozone, believes that humans are responsible, and will face repercussions if temperatures continue to increase.

"Things are changing and there's no doubt that it's as a result of human activities," said Mario Molina, a Mexican who shared a Nobel prize in chemistry in 1995 for groundbreaking work on chlorofluorocarbon gases and their threat to the Earth's ozone layer. "Long before we run out of oil, we will run out of atmosphere," he said.

"You keep changing the temperature gradually but then suddenly things change dramatically. Trying to keep it (warming) below two degrees (Celsius) means we want to keep the change at most twice or three times what it has changed already. And that's because it's unrealistic to change it by less, because of what we have already done," Molina said.

"The idea to keep the temperature change not above 2.5 (degrees Celsius) is precisely to reduce the possibility of these tipping points happening," he added.

Molina made these comments while addressing attendees of an Inter-American Bank meeting in Miami. While he said that "tipping points" were inevitable if warming continues, he was unable to say exactly how much warmer temperatures could become before becoming critical.

» Reuters Environment