It is very safe to say that man is wasteful, he fouls and pollutes without regard to the land, plants, people, and animals, and he is arrogant in his "right" to do all of this. But is man responsible for the greenhouse effect?
To begin with, we must understand that the effect is actually the holding in of heat. This is caused by the properties of certain gases in the atmosphere, and since those are natural properties, it is nature that is responsible for the effect itself.
But does man add to the greenhouse effect on Earth, or is there another cause? First let me say that there is nowhere near the amount of knowledge to give an accurate answer to this, either way. There also isn't enough data that has been collected to form any truly valid opinions, though some scientists and other people attempt to on the scanty data and knowledge we have. Instead, let's look at what the greenhouse effect is and what causes it.
The term was originally coined from observations on what happens when sunlight passes through the glass of a greenhouse. Glass, being mostly silicon, reflects certain frequencies of sunlight while allowing others to pass through. Among those that are allowed through are the frequencies closer to the red end of the spectrum, including infrared, which produces heat.
Greenhouse gases function in nearly an identical way. In fact, a good definition of a greenhouse gas would be any substance that is gaseous form that allows heat in, but halts or slows it from leaving.
There are literally hundreds of greenhouse gases, some of them made of very complex molecules. The three biggest in regard to the earth, in order, are water vapor, methane, and carbon dioxide. Water vapor is actually many times more potent than all of the other greenhouse gases combined, at least on Earth. The reason is that it not only holds heat in, it actually focuses it like a magnifying glass.
What may come as a big shock to many people is that greenhouse gases are not bad, and in fact, without them, we could not survive. The reason for this is two-fold. First, as with the glass of a greenhouse, some rays from the sun are reflected back out into space. These include ultraviolet rays that would quickly kill everything on Earth. Second, they allow the earth to retain the heat that is absorbed. Without them, the earth would be an icy ball. The atmosphere of Mars is almost entirely carbon dioxide, but it is so thin that at the greater distance from the sun, it can't retain enough heat to make a great deal of difference, and without the addition of water vapor, mars is a very cold place.
Further, methane is produced from the natural breakdown of plant life. Carbon dioxide is necessary for plants to live. Let's not forget that from fossil records, we know that carbon dioxide was far more abundant in the past than it is now. This could be why there are not as many species and such a diversity of plant life as there was back then.
Who is responsible for the effect? Mother nature, thank goodness. Is it a reason for concern? Not unless we start becoming so arrogant that we think that we are more powerful than, and important than mother nature.