Final answer:
Venus is hot primarily due to a runaway greenhouse effect caused by high concentrations of CO₂, which traps infrared radiation and raises the surface temperature to extreme levels. The thick CO₂ atmosphere acts as a blanket, preventing the planet from cooling effectively. This dramatic example helps to underscore the potential implications of increasing greenhouse gases on Earth.
Step-by-step explanation:
The reason why Venus is so hot is primarily due to a runaway greenhouse effect caused by the massive amounts of carbon dioxide (CO₂) in its atmosphere. The insolation, or incoming solar radiation, that Venus receives is only slightly greater than that of Earth due to its closer proximity to the Sun. However, the dense CO₂ atmosphere on Venus traps the infrared radiation, preventing it from being re-radiated back into space. This causes the surface temperature to increase substantially, maintaining a much hotter environment than on Earth.
The presence of greenhouse gases like CO₂ is a key factor in determining a planet's temperature. On Venus, the effect is drastically enhanced due to the thick CO₂ atmosphere, which acts like a thermal blanket, creating surface temperatures high enough to melt lead. This runaway greenhouse effect results in a surface temperature of over 700 Kelvin, much higher than what can be attributed to the Sun's irradiance alone.
The study of the greenhouse effect on Venus provides a cautionary example of how increasing levels of greenhouse gases can lead to significant global warming, as seen with concerns on Earth today. Thus, the Venusian climate is a subject of interest when considering the potential future impact of rising CO₂ levels on our own planet's climate and habitability.