A recent letter to the editor asserted that man-made global warming cannot occur because there is a fixed amount of different kinds of matter in the Earth.

Although there is a fixed amount of elements such as carbon and oxygen in the world, they can be combined in different ways to create different molecules such as carbon dioxide. And man did not invent carbon dioxide, it existed on earth long before humans arrived. Man's role has been to bring carbon to the Earth's surface where it combines with oxygen to create carbon dioxide.

Carbon dioxide levels in the atmosphere have varied over the Earth's long history. Some mass extinctions in Earth's long past were caused by enormous volcanic eruptions many time larger than those experienced today. These early eruptions spewed vast amounts of carbon into the atmosphere where it combined with oxygen to form carbon dioxide. This increased concentration of atmospheric carbon dioxide created a rapid increase in the Earth's temperature, leading to the extinction of many forms of life on Earth.

Today it is not massive volcanoes that are bringing carbon to the surface of the Earth but oil wells and coal mines. When these materials are burned in our cars and power stations, they release carbon into the atmosphere to create atmospheric carbon dioxide. Because carbon dioxide can remain in the atmosphere for hundreds of years, its impact on global temperature is long lasting.

This is not a hoax. It is the fact of what is happening. The hoax occurs when individuals assert that efforts to limit carbon dioxide emissions is a way to control people and take away their liberties and freedoms.

Don Hofstrand, Mason City