One of the factors that affects the world's environmental conditions is the greenhouse effect. Climate scientists often blame the greenhouse effect for contributing to Earth's environmental woes, but it has a vital positive effect on the planet as well. Without this atmospheric condition, life on Earth would be vastly different, or even nonexistent.

The greenhouse effect refers to the ability of the atmosphere to trap the sun’s heat, increasing the temperature of the planet. When the sun’s energy reaches Earth, the atmosphere absorbs some of it on the way down, and then absorbs more when that energy reflects back off the surface during the day. This trapped energy heats up the atmosphere, increasing the temperature of the planet and distributing warmth to its night side, when solar heating is unavailable. The denser the atmosphere, and the higher the concentration of energy-holding molecules like water vapor and carbon dioxide, the more energy the atmosphere can trap.

The greenhouse effect is important, because it contributes to the survival of life on Earth. Without the greenhouse effect, the temperature of the planet would be similar to conditions experienced on the moon. On the lunar surface, with no atmosphere to mediate temperature swings, the surface can reach 134 degrees Celsius (273 degrees Fahrenheit) during the day and -153 degrees Celsius (-244 degrees Fahrenheit) at night. This dramatic temperature change required NASA to develop specialized gear to protect astronauts from both extremes for the moon landings. A similar temperature swing on Earth would have produced an environment hostile to most living things.

Unfortunately, while a moderate greenhouse effect is vital to life, an elevated greenhouse effect can be dangerous. Since the Industrial Revolution, the widespread adoption of fossil fuels has increased the amount of carbon dioxide, water vapor, and other greenhouse gases in the atmosphere. According to a study by the Carbon Dioxide Information Analysis Center of the United States Department of Energy, carbon dioxide levels have increased 39.5 percent since 1750, while levels of methane in the atmosphere have jumped by 150 percent. Climate scientists point to this increase in heat-trapping gases as one of the reasons global temperatures have risen during this period.

One of the chief concerns about an increase in the greenhouse effect is that the changes can become self-sustaining. As more greenhouse gases enter the atmosphere, its ability to trap heat increases. As the warmth of the atmosphere increases, the amount of water vapor it can hold increases as well, further boosting the effect. In addition, increased global temperatures threaten to release large amounts of carbon that is currently frozen into permafrost zones, also exacerbating the problem. Excessive heat retention could lead to massive changes in natural water distribution and available land mass on a global scale. The effect of mitigating factors, such as increased cloud cover reflecting sunlight back into space, is not well understood.