Glen Luckman Greenhouse Warming

The Effects of Global Greenhouse Warming

Author: James Nash

The Earth and Venus are near each other in the Solar System, and are similar in size, density, and composition. Based on our understanding of the origin of the Solar System, we would expect that their initial atmospheres would have been rather similar. Yet the present atmospheres of the two planets could hardly be much more different than they are. How did this come to be? The reason is thought to lie in what is termed the “Runaway Greenhouse Effect”.

Sunlight falling on the surface of a planet is primarily in the visible part of the spectrum. However, the reflection of light from the surface tends to produce light of longer wavelength called infrared (IR) radiation (also known as radiant heat; IR radiation is the heat that we sense being radiated from a hot surface like a hot piece of metal).

Now, because of their molecular structures, certain gases like carbon dioxide and water vapor (and many others) have the property that they are essentially transparent to visible light but absorb IR radiation very strongly. Such compounds are sometimes termed greenhouse gases because, if they are present in a planetary atmosphere, they absorb the scattered IR radiation and tend to raise the temperature of the atmosphere by trapping solar energy. (The analogy with a real greenhouse is imperfect because the mechanism by which a greenhouse stays warm is different, but it is sufficiently good that the name “(Planetary) Greenhouse Effect” is now the common one for this phenomenon.)

The greenhouse effect occurs for all planetary atmospheres containing greenhouse gases, and is responsible for their being warmer than would be the case otherwise. The greenhouse effect by itself could not account for the conditions that we find on Venus. However, under certain conditions we believe the greenhouse effect can “run away”. For example, consider the case of a planet like the Earth. The Earth has enormous amounts of two greenhouse gases: water vapor and carbon dioxide. However, for the Earth most of the water and carbon dioxide are not in the atmosphere. The water is mostly in the oceans, and the carbon dioxide is mostly bound chemically in rocks made from compounds that chemists call carbonates (for example, limestone).

Now suppose we increased the effectiveness of greenhouse heating of the Earth’s atmosphere, for example by increasing the amount of solar radiation falling on it, or by increasing the concentration of greenhouse gases in the atmosphere (for example, by burning fossil fuels, which produce water vapor and carbon dioxide as byproducts of burning). We would then expect the temperature to rise in the atmosphere (assuming no other effects intervened—a big “if” in the realistic case since the atmosphere is complicated). This would be a greenhouse effect.

It would become a runaway greenhouse effect if the rising temperature approached the boiling point of water, because then the oceans would begin to convert to water vapor, the water vapor would increase the effectiveness of heat trapping and accelerate the greenhouse effect, this would cause the temperature to rise further, thus causing the oceans to evaporate faster, etc., etc. (This type of runaway is also called a “positive feedback loop”.) When the oceans were gone the atmosphere would finally stabilize at a much higher temperature and at much higher density, because all the water would now be in the atmosphere.

We can envision even a further runaway stage in this scenario. Suppose the preceding runaway raised the temperature so high that chemical reactions begin to occur that drive the carbon dioxide from the rocks into the atmosphere (the process is called sublimation; a few hundred degrees Celsius would be sufficient). Then another runaway would occur as the carbon dioxide feeding into the atmosphere would accelerate the heating, which would in turn accelerate the transfer of carbon dioxide from the rocks to the atmosphere.

The atmosphere would finally stablilize at a still higher temperature and pressure after all the carbon dioxide had been driven from the rocks. In fact, we believe that if this sequence were to take place on the Earth, the resulting temperature and pressure of the atmosphere left behind would not be very different from that for present-day Venus: the atmospheric termperature would be hundreds of degrees Celsius and the pressure would be maybe 100 times greater than it is today.

Thus, we believe that in the case of Venus the initial solar heating kept oceans from forming, or kept them from stayiBy: oneclickdoctor

If the greenhouse effect has again been currently in the news, it is probably because it is once again being blamed for causing global warming. Stronger hurricanes, periods of extreme weather, heat waves, the frequency of the El Nino phenomenon, these are all attributed to global warming. But how does the greenhouse effect figure in all these?

What is the greenhouse effect?
The greenhouse effect is the ability of our planet’s atmosphere to trap and contain heat. This heat is sourced from the sun and is reflected back towards the atmosphere. Certain gases are responsible for this entrapment and they include carbon dioxide, nitrous oxide, methane, fluorinated compounds and water vapor. Other man-made chemicals are also capable of retaining heat within the atmosphere.

In itself, the greenhouse effect is not essentially evil. In fact, it is this very phenomenon that has produced life on earth as we know it. Think of the greenhouse effect as a natural thermal blanketing for our planet, maintaining a surface temperature that is just right to encourage organisms to grow and survive. Without this blanketing, the earth’s climate would be too cold – about 59F lower than the average – for our planet to be able to sustain life successfully.

How does the greenhouse effect contribute to global warming?
For more than 4 billion years, the greenhouse effect has kept our planet’s temperature at a friendly level. Gases found in the atmosphere act to trap heat and keep our planet insulated, able to sustain itself. Problems only began to arise when scientists noticed that certain practices and human activities contribute to the modification of this process.

When the Industrial Revolution began, we also devised many ways of using fossil fuel for oil, coal and gas. The only way to utilize these fuels was by burning. As industrialization continued to expand, so did the practice of fossil fuel burning, thereby releasing gases into the atmosphere. The only problem was that these gases had nowhere else to go and have continued to build up over the years.

By building up, they cause the atmosphere to become more efficient in trapping heat, causing climates to turn warmer. This unnatural or man-made result is referred to as global warming.

How global warming affects us
We have been experiencing the effects of global warming for the past years and most of these are felt through changes in the climate. However, it’s important to note that climate change is brought about by other factors and not just as an indirect result of the greenhouse effect. Some of these factors include changes in the circulation of the oceans, changes in our planet’s orbit and even changes in the intensity of the sun itself.

Global warming involves increase in the average temperature of the earth’s atmosphere near its surface. While global warming is nothing new to our planet (it has occurred over long periods in the earth’s 4.5-billion-year history alternating with ice ages), it is only now when its drastic changes on a global scale has dire consequences not just for human kind but also to the millions of species that depend upon the earth for sustenance.

A famous example of the effect of global warming is the increase in sea level, brought about by the melting of glaciers. This is a problem not readily seen nor felt in countries or regions that lie on higher ground, but for many areas, this could mean land (and subsistence opportunities) lost to sea. A 0.3-meter increase in sea level for example, can eat up about 15 meters of beach.

As temperatures rise, countries that have agricultural practices firmly dependent on the regularity of glacier-melting will suffer greatly. For many regions in the world, the melting of snowpacks from the mountains means water for plant irrigation and electricity. If the melting occurs at a bad time, the planting and harvesting of crops will be significantly disrupted, causing problems in the economy on a local and national level.

With global warming, abrupt weather changes may also be experienced, such as heat waves that last longer and occur with more frequency, stronger storms and hurricanes and even changes in the behavior of the winds. Warmer climate will also contribute to the displacement of plants and animals, as those who depend upon lower temperature regions to survive will need to move to higher elevations and latitudes. For plants and animals who cannot adapt, it could mean extinction.

Healthwise, diseases that right now are currently limited by the location and living habits of their carriers have the possibility of invading areas that didn’t have a problem with them before. An example of this is malaria, along with other diseases caused by mosquitoes.

Mosquitoes thrive in tropical settings and as more and more regions become warmer, mosquitoes will expand their range. They will now be able to go to areas that they usually do not inhabit because of the temperature. This exposes the formerly unexposed population to the health risks caused by mosquito-borne diseases that also include dengue and elephantiasis.

Facing global warming
The balance of life and competition among species may also be disrupted, in more ways than are currently foreseen. In fact, with global warming, certain lifestyles and animal behavior that we have enjoyed so far may also disappear, unless we do something to try to correct and arrest the problem.
ng around if they did form, and the subsequent lack of rainfall and failure of plant life to evolve kept the carbon dioxide in the atmosphere rather than binding it in the rocks as is the case for the Earth; thus, Venus has an environmental disaster for an atmosphere.

Glen Luckman Greenhouse Warming