A process totally unrelated to global warming will cause the Earth's temperatures to rise, leading to the evaporation of the oceans. Researchers predicted the oceans will have completely disappeared within a billion years.

By looking at the evolution of older stars, researchers determined the Sun will behave in a similar manner; if this is the case its "luminosity" will increase as it ages, a National Center for Scientific Research (CNRS) news release reported.

As solar radiation increases the Earth's climate will also heat up over the next hundreds of millions of years.

Water vapor is actually a greenhouse gas, so as the oceans evaporate the Earth's atmosphere will warm. The researchers believe the "runaway climate" will cause the oceans to turn into vats of boiling water that will eventually evaporate and disappear.

The unstable environment would make it impossible for the climate to maintain an average temperature of about 55 degrees Fahrenheit. This phenomenon could have been linked to Venus "turning into a furnace" in the ancient past.

The research team used three-dimensional climate models that portrayed the phenomenon of luminosity; until now only one-dimensional models. The highly simplified astrophysical (one-dimensional) models failed to take outside features into account such as "seasons and clouds."

The new model predicted the Earth would start losing its oceans and becoming a "new Venus" in about 150 million years.

According to the model the tipping point will arrive when the Sun reaches a flux of about 375 W/m2 (today it is 341 W/m2 ) and the Earth's surface temperature is about 150 degrees Fahrenheit (70 degrees Celsius). This is predicted to happen about one billion years in the future, and it will be what sets off the "runaway climate."

"This difference is due to atmospheric circulation: while transporting heat from the equator to the mid-latitudes, it dries these warm regions and reduces the greenhouse effect in the areas where it is most likely to enter a runaway state. Increased solar flux appears to intensify this atmospheric circulation, drying sub-tropical regions even more and stabilizing the climate for several hundred million years before it reaches the point of no return," the news release reported.

This new model also shows the "parasol effect," which is the ability of clouds to reflect solar radiation. This ability is expected to decline over the next billion years, contributing to the atmospheric warming.

These findings could also be used to help scientists determine what planets are within habitable zones of their host stars. The models showed a planet can get up to 0.95 astronomical units3 (about five percent less than the distance between Earth and the Sun) from a star before losing all of its liquid.