Extraterrestrial atmosphere star undergoing runaway greenhouse effect. For planets in the habitable zone, it was thought that water photolysis would be strongly limited by cold-trapping of water vapour in the lower atmosphere. However, the extent of HO cold-trapping depends strongly on the amount of non-condensible gases in the atmosphere such as nitrogen N and argon. In the absence of such gases, the likelihood of build-up of oxygen also depends in complex ways on the planet's accretion history, internal chemistry, atmospheric dynamics, and orbital state. Therefore, oxygen, on its own, cannot be considered a robust biosignature. The ratio of nitrogen and argon to
Sustainability at the University of British Columbia Sustainability at the University of British Columbia Climate change is now the most serious global environmental threat. Its potential impacts include global warming, sea level rise, and increased extreme weather events. Climate change is a direct consequence of elevated greenhouse gas concentrations in the atmosphere. Greenhouse gases are gases that trap heat in the atmosphere. Some examples include Carbon dioxide, Methane, and Nitrous oxide. They are emitted from fossil fuel burning. Electricity production generates the largest share of greenhouse gas emissions. Moreover, other sources include transportation, industry, and agriculture. These gases are said to make the planet warmer by “thickening