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A study from the University of Victoria is suggesting that our atmosphere is far more susceptible to a runaway greenhouse effect than previously assumed.
The phenomenon occurs when a planet absorbs more solar energy than it can give off in return. That causes surface water to evaporate, fill the atmosphere with steam, and heat the planet until it’s no longer habitable — kind of like what’s seen on Venus.
For the study, a team of astronomers used computer modeling to calculate the thermal radiation limit of the “runaway greenhouse” effect.
By using computer models, researchers Tyler Robinson and Colin Goldblatt discovered a lower thermal radiation threshold for the runaway greenhouse process. Their model took new measurements into account of how water and carbon dioxide absorb different wavelengths of light.
Their finding means that planetary atmospheres are far more fragile than we thought, and that the habitable zones of solar systems are narrower than assumed. A habitable zone is the band around a star within which planets can maintain liquid water. And in fact, the new study has deep implications for astronomers and astrobiologists; they may have to reset their notions of exoplanet habitability. What’s more, some extrasolar planets declared as potentially habitable may need to have their status revoked.
“It used to be thought that a runaway greenhouse was not theoretically possible for Earth with its present amount of sunlight,” study co-author Dr. Colin Goldblatt, a professor at the University of Victoria in Canada, told National Geographic. “We’ve shown that, to the contrary, it is theoretically possible. That doesn’t mean it’s going to happen — but it’s theoretically possible.”
According to Robinson and Goldblatt, it’s likely impossible for human activity to induce a runaway greenhouse effect. To do so, we’d have to raise the concentration of CO2 in the atmosphere to around 30,000 parts per million. This is considerably more that could be attained even if we burned all the available fossil fuel reserves on the planet 10 times more to be exact. editor@ictpost.com
