Climate change, greenhouse gases, the greenhouse effect, emissions, rising sea levels, how does all this connect? Here is a primer on the issue (it will be expanded in time).
First, climate change is a naturally occurring phenomenon. The earth has had many ice ages in the past, and many warm periods, plus all those transitional times in between. So we aren’t exactly concerned about climate change in and of itself. The cause for all the concern today is that human activities have accelerated climate change, and have created conditions that could make the earth warm faster and to a greater extreme than has ever happened before.
So, how have humans accelerated climate change? Basically, we are increasing the amount of insulation for our home, the earth. The atmosphere really does form a sort of greenhouse around the earth. In a greenhouse, the transparent walls and ceiling allow sunlight (energy) to enter and warm up the air in the house, but reduce air exchange with the colder outside air because those walls and ceilings are solid. Human life, as well as the life of all other organisms on earth, depends on this greenhouse effect. Without this insulation, the temperature of the earth would be well below freezing all the time. But, humans have rapidly increased the amount of greenhouse gases in the atmosphere, so that more heat is trapped by the atmosphere than was before. To see a long history of the relationship between C02 in the atmosphere and global temperature, see this EPA website.
So, what are these greenhouse gases? Greenhouse gases are not all scary chemicals; in fact, the most common greenhouse gas is water vapor. The second most common greenhouse gas is carbon dioxide, or CO2. Methane, or CH3, is the third most common greenhouse gas, followed by nitrous oxide, ozone and CFCs. The most common greenhouse gases, you will notice, are very important gases for life on earth. We all exhale CO2, and plants depend on CO2 to photosynthesize. Methane is a common byproduct of metabolism, perhaps most popularly known from cow flatulence (yes, cow farts).
The problem is, we have made CO2 (maybe we’ll talk about the other greenhouse gases later) far more common in the atmosphere than it has been ever before. How have we done this? In many ways, but most specifically by releasing carbon that was stored in plant and animal remains deep below the surface of the earth–what we call fossil fuels. These fossil fuels, especially oil and coal, really are like fossils: they are formed by biogeochemical processes acting on dead plants and dead animals over long periods of time. As dirt and rocks cover over these remains, the carbon is stored where it cannot easily enter the atmosphere. But when we dig or pump up these fossil fuels and burn them up to heat our houses, run our cars, and light up the darkness, we release their carbon into the atmosphere as CO2. These fossil fuels have been buried for millions of years, and then in just two centuries we have burned them at an absolutely amazing rate. That is a lot of stored carbon that is entering the atmosphere.
So it is really a very easy thing to understand. By removing natural stores of energy from deep within the earth, we are adding more CO2 to the naturally occurring greenhouse gases in the atmosphere, creating a natural heating effect. The unnatural thing is the rate, or rapidity, at which we are doing this. Much more detail can be added to this explanation, but this is all you need to understand the basic issues regarding climate change, greenhouse gases, and fossil fuels.
Changes in land use also has a big effect on climate change. Check back soon for an explanation of this. In the mean time, check out the explanations of climate change on PBS and at Wikipedia.
