From Mensagenda - March 2007

The Future: The Greenhouse Effect

by Mary Abbey

The Enhanced Greenhouse Effect

Today the Intergovernmental Panel on Climate Change issued its first volume of its recent assessment on global warming, and, yes, global warming is real, and is assuredly caused by human activities, with a certainty of 90 percent. How in the world are people affecting the climate of the entire Earth?

Remember that the majority of energy striking the surface is reradiated as infrared and passes through the atmosphere to space. The only heat trapped is absorbed by greenhouse gases and then radiated again. The more molecules that can absorb infrared and redirect its energy back toward the surface, the warmer we will be. The increasing numbers of these gases from anthropogenic sources cause additional heat to be retained in our atmosphere. This is known as the enhanced greenhouse effect.

The major culprit, but not by any means the only one, is carbon dioxide. Since the Industrial Revolution, about 1750, global atmospheric concentrations of CO2 have risen by about 35 percent. Most of this is due to the combustion of fossil fuels. In the process of burning organic material, oxygen combines with carbon to produce carbon dioxide. If we burn wood, paper, oil, gasoline, coal, or natural gas, we increase the quantities of these greenhouse gases in the atmosphere, and add to global warming. Not surprisingly, we like our lifestyle that depends on fossil fuels, and other countries would also like to have our level of consumption. Thus, without major changes, the quantities of carbon dioxide in the atmosphere will continue to rise, and we will continue to warm up.

So why are we just recently aware of the problem? Scientists have known for many years that the levels of greenhouse gases are going up. However, earlier measurements of temperature may have been taken at incorrect heights to give us an accurate picture of conditions in the troposphere, where our weather occurs. The effects of global warming may have been neutralized by the effects of natural cycles. Normally, we would be in a cooler period at this time, but are suffering increasingly warmer years. And then there’s ABC, the Asia Brown Cloud.

Along with the burning of biomass, the burning of coal is contributing to a large brown cloud of aerosols and carbon monoxide that covers a good part of Asia and the Pacific Ocean. This Asia Brown Cloud, two miles thick during the winter maximum, reflects light back to space so that up to 10 percent less sunlight reaches the surface. This affects local weather and can be blamed for several droughts, including that of the Sahel, the area south of the Sahara Desert. The ABC likely has significantly affected the average temperature of the world by keeping parts of the globe cooler. In this country more and more we are cleaning the particulate matter from our emissions, thus blocking less sunlight and allowing more warming to occur. The quantities of greenhouse gases have continued to rise in our atmosphere, and the temperature rise and its effects are now quite apparent.

So what are those effects? I’ll talk about that next time, but, meanwhile, add this topic to your list of interests, if it’s not already there. This is an important one.