Atmosphere of Venus water and subsequent rise of the levels of other greenhouse gases. Despite the harsh conditions on the surface, the atmospheric pressure and temperature at about 50 km to 65 km above the surface of the planet is nearly the same as that of the Earth, making its upper atmosphere the most Earth-like area in the Solar System, even more so than the surface of Mars. Due to the similarity in pressure and temperature and the fact that breathable air (21% oxygen, 78% nitrogen) is a lifting gas on Venus in the same way that helium is a lifting gas on
Flash-gas (petroleum) to its combustion. As of 2009, energy-related CO emissions made up more than 80% of total U.S. greenhouse gas emissions. Flare and flash gas both contain GHGs and therefore contribute to their release into the atmosphere, estimates of their emission levels during petroleum production vary due to largely unmeasured release of flash gas and other forms of fugitive emissions. One study estimated a 40% increase in the atmospheric concentration of the GHG carbon dioxide (CO) is due directly to human activities since 1750. GHGs other than CO which are produced during petroleum operations are also a concern to the environment.