The greenhouse effect is a biological process in Earth’s atmosphere in which certain gases bind together and form what is essentially a layer of insulation. This insulation traps warmth and solar radiation. It is a natural process that is widely believed to be essential to life on the planet, since without it heat from the sun would escape and the planet could grow frigidly cold as a result. Just the same, certain “greenhouse gases” have gotten a bad reputation in recent years for the negative ways in which they interact with the process. Chemical emissions and pollution can cause the insulation to be thicker or thinner than normal, for instance, and might even be able to cause holes or perforations. Greenhouse gases are often blamed for the phenomenon known as “global warming,” and the greenhouse effect is certainly a part of this — but the process isn’t usually viewed as a problem in and of itself.
Earth’s atmosphere is more complex than many people realize. The composition of chemicals and particulates changes as things go up from the surface, and the upper edge of the atmosphere essentially acts like a dense barrier that allows sunlight to filter through while trapping heat. In some respects, the layer acts like the protective covering of a greenhouse that insulates plants and keeps warmth and humidity inside, and this is where it gets its name.
During the daytime, the earth absorbs heat directly from the sun and reflects it out to space. Without an atmosphere with greenhouse-like insulation, this heat would escape at night in the absence of direct sunlight and temperatures would fall rapidly. Instead, gaseous molecules absorb the heat given off by the planet and re-radiate it out in all directions, essentially reabsorbing it and redistributing it again and again. This keeps the surface relatively warm and the average temperature comfortable, and the phenomenon is essential to life. Even places that see cold nights during the depths of winter are no comparison to how bitter things would get with no atmospheric shielding.
Understanding Greenhouse Gases
The gases that make up this layer are commonly known as “greenhouse gases.” These are trace gases of mainly water vapor, carbon dioxide, methane, ozone, and nitrous oxide. It’s important to note that Earth's atmosphere largely consists of nitrogen and oxygen, but these are not specifically greenhouse gases, nor do they contribute to the overall effect.
Potential Problems with Emissions
Scientists started using the term "greenhouse effect" in the 1800's. At that time it had no negative connotation. In the mid 1950's the term began to be associated with global warming and also with the negative effects of the modern industrial age. This enhanced effect, as it's sometimes known, is the result of burning fossil fuels. According to many scholars, fuel-burning activities release carbon dioxide(CO2) into the atmosphere at the rate of about 3 gigatons (3 billion metric tons) per year. This is in addition to the gas that already exists naturally in the atmosphere, and the artificial inflation is what has many people concerned.
CO2 absorbs heat, and significant increases in atmospheric CO2 will tend to raise the global temperature, possibly contributing to what’s known in much of the literature as global warming. Simply put, if greenhouse gases act like a blanket to keep our planet warm, humans are thickening that blanket and should expect to see warmer temperatures and more relative humidity as a result.
Other Planetary Examples
A look to the neighboring planets of Venus and Mars can be a good way to illustrate what happens when the greenhouse layer becomes too thick or too thin. Temperatures on Venus soar because of its very thick atmospheric density, and life cannot be sustained in large part because of how very hot the surface is for much of the day. Mars, on the other hand, has such a thin atmosphere that the planet is very cold. Nearly all of the heat that reaches Mars escapes before it has a chance to do things like sustain plant life. Relative distance from the sun plays a part in the global temperatures of the inner planets, certainly, but a greenhouse effect or lack thereof is one of the biggest drivers of climates everywhere.