Atmospheric heating could turn Earth into another Venus
WASHINGTON: A new study has found that prolonged heating of the atmosphere can shut down plate tectonics and cause a planet's crust to become locked in place, a situation which could make Earth another Venus.
The team, which conducted the study, included researchers from Rice University in US, the University of British Columbia in Vancouver, Canada, and Louis Moresi of Monash University in Clayton, Australia.
According to lead author Adrian Lenardic, associate professor of Earth science at Rice University, the research team wanted to better understand the differences between the Earth and Venus and establish the potential range of conditions that could exist on Earth-like planets beyond the solar system.
The findings may explain why Venus evolved differently from Earth.
The two planets are close in size and geological makeup, but Venus' carbon dioxide-rich atmosphere is almost 100 times denser than the Earth's and acts like a blanket. As a result, Venus' surface temperature is hotter than that of even Mercury, which is twice as close to the sun.
The Earth's crust, along with carbon trapped on the oceans' floors, gets returned to the interior of the Earth when free-floating sections of crust called tectonic plates slide beneath one another and return to the Earth's mantle.
"We found the Earth's plate tectonics could become unstable if the surface temperature rose by 100 degrees Fahrenheit or more for a few million years," said Lenardic.
The new findings show that prolonged heating of a planet's crust via rising atmospheric temperatures can heat the deep inside of the planet and shut down tectonic plate movement.
"The heat required goes far beyond anything we expect from human-induced climate change, but things like volcanic activity and changes in the sun's luminosity could lead to this level of heating," said Lenardic.
"We found a corresponding spike in volcanic activity could accompany the initial locking of the tectonic plates" he said.
"This may explain the large percentage of volcanic plains that we find on Venus," he added.
According to Lenardic, one of the most significant findings in the new study is that the atmospheric heating needed to shut down plate tectonics is considerably less than the critical temperature beyond which free water could exist on the Earth's surface.
"The water doesn't have to boil away for irrevocable heating to occur," said Lenardic. "The cycle of heating can be kicked off long before that happens. All that's required is enough prolonged surface heating to cause a feedback loop in the planet's mantle convection cycle," he added.
World CO2 levels highest for 650,000 yrs
LONDON: Scientists have warned that climate change could soon begin to get out of control, with concentration of carbon dioxide in the atmosphere touching a record high.
Scientists at the Mauna Loa observatory in the US state of Hawaii say that CO2 levels in the atmosphere now stand at 387 parts per million (ppm), up almost 40 per cent since the industrial revolution and the highest for at least the last 650,000 years.
Based on some 11,000 ft high volcano, the Mauna Loa observatory is regarded as producing among the most reliable data as its remote location ensures that its sensors are not confused with other possible sources of the gas.
According to the US National Oceanic and Atmospheric Administration, the latest figures also confirm that carbon dioxide, the chief greenhouse gas, is accumulating in the atmosphere faster than expected.
"Despite all the talk, the situation is getting worse. Levels of greenhouse gases continue to rise in the atmosphere and the rate of that rise is accelerating. We are already seeing the impacts of climate change and the scale of those impacts will also accelerate, until we decide to do something about it," Martin Parry, co-chair of the Intergovernmental Panel on Climate Change's working group on impacts, was quoted as saying by the British daily Guardian.
According to the report, the annual mean growth rate for 2007 was 2.14 ppm - the fourth year in the last six to see an annual rise greater than 2 ppm. From 1970 to 2000, the concentration rose by about 1.5ppm each year, but since 2000 the annual rise has surged to an average 2.1ppm.
Researchers suggest the trend could mean that the Earth is losing its natural ability to absorb billions of tonnes of CO2 each year.