What does the greenhouse effect refer to?

The greenhouse effect refers to the warming of Earth’s surface due to the trapping of heat by greenhouse gases in the atmosphere. When solar radiation reaches Earth, some of it is reflected back to space, while the rest is absorbed and warms the planet's surface. The Earth then emits this heat in the form of infrared radiation. Greenhouse gases, such as carbon dioxide, methane, and water vapor, absorb some of this infrared radiation and re-radiate it back to the surface, effectively trapping heat within the atmosphere. This process is essential for maintaining temperatures that support life on Earth. Without the greenhouse effect, our planet would be too cold to sustain most forms of life as we know them today.

In contrast, the other options describe processes or phenomena unrelated to the greenhouse effect. For instance, the cooling of Earth's surface is the opposite of what occurs during the greenhouse effect. The process of photosynthesis is a biological process by which plants convert sunlight into energy, and while it is related to the sunlight that drives the greenhouse effect, it does not describe the warming mechanism itself. The increase in solar radiation reaching Earth does not encompass the concept of heat being retained by the atmosphere, which is a key characteristic of the greenhouse effect.