© iStockphotoScientists have solved one of the great mysteries of our geological past: Why the Earth's surface was not one big lump of ice four billion years ago when sun radiation was much weaker than today.
Scientists have solved one of the great mysteries of our geological past: Why Earth's surface was not one big lump of ice four billion years ago when Sun radiation was much weaker than today. Scientists have presumed that Earth's atmosphere back then consisted of 30 percent CO2 trapping heat like a greenhouse. However, new research shows that the reason for Earth not going into a deep freeze at the time was quite different.
In 1972, the late, world famous astronomer Carl Sagan and his colleague George Mullen formulated "The faint early Sun paradox. " The paradox consisted in that Earth's climate has been fairly constant during almost four of the four and a half billion years that the planet has been in existence, and this despite the fact that radiation from the Sun has increased by 25-30 percent.
The paradoxical question that arose for scientists in this connection was why Earth's surface at its fragile beginning was not covered by ice, seeing that the Sun's rays were much fainter than they are today. Science found one probable answer in 1993, which was proffered by the American atmospheric scientist, Jim Kasting. He performed theoretical calculations that showed that 30% of Earth's atmosphere four billion years ago consisted of CO2. This in turn entailed that the large amount of greenhouse gases layered themselves as a protective greenhouse around the planet, thereby preventing the oceans from freezing over.