Linkages between ‘Green-House effect’, ‘Ozone depletion’ and ‘Global Climate Change’

Green House Effect:

The best-known greenhouse gas is carbon dioxide (CO,). Carbon dioxide is breathed out or otherwise given off by living organisms (including plants) as they undergo aerobic respiration, and is taken in by green plants during photosynthesis.

A small amount of carbon dioxide in the atmosphere is an absolute necessity for life on Earth; without it the planet would be too cold to support living organisms, and plants would lack an essential raw ingredient. But an excess of carbon dioxide will cause the Earth’s surface to heat up abnormally.

Clearly, we humans are very quickly adding to the amount of carbon dioxide in the atmosphere. In 1950 the average annual concentration of carbon dioxide was about 250 ppm (parts per million); this increased to 316 ppm by 1950 and by 2007 it had grown to nearly 460 ppm. The CO, content of the atmosphere continues to increase.

The primary way we are increasing the CO₂ content of the atmosphere is through the burning of fossil fuels: coal, oil, and gas. For millions of years, the carbon in these fuels has been out of atmospheric circulation, buried deep under the surface of the Earth.

But suddenly, over a period of just two centuries (and especially during the last few decades), we have released massive amounts of this fossilized carbon back in the atmosphere.

In 2004, for instance, an estimated 6.5 billion tons (5.9 billion metric tons of carbon were released worldwide by the combination of fossil fuels-slightly over 1.1 tons of metric ton) of carbon per person on Earth. E ton of pure carbon released forms approximate of 3.66 tons of C0₂, so approximately 23.8 billion tons (21.6 billion metric tons) of CO, were leased into the atmosphere simply by the burning of fossil fuels in 2004 or 21 trillion kg of Co Given that 500g of CO,, occupies about 8.75 cubic feet at room temperature at sea level, 21 trillion kg of CO., is equivalent to more than 400 trillion cubic feet of trillion m³ of CO-,, of course, the actual volume of C0₂ depends on temperature and pressure conditions in various parts of the atmosphere.

Ozone depletion:

It may appear that the ozone story has come to a happy closure; however, despite the 1990 and 1992 agreements, the story is not over yet. Even with the complete phase-out of CFCs and other Chlorine-bearing chemicals, stratospheric chlorine concentrations are expected to remain high well into the twenty-first century as already released CFC molecules rise from the troposphere into the stratosphere (a CFC molecule can take 15 years to make it away up from the Earth’s surface to the stratospheric ozone layer).

Furthermore, despite the Montreal Protocol and its amendments, as of the early 1990s some developing countries had actually increased their use of CFCs (most CFCs still originate from the industrialized world, however). Realizing the urgency of the situation, some countries have moved up the phase-out schedules; for instance, the 12 members of the European Union promised to stop producing CFCs by the end of 1994.

Even with the accelerated phase-out, the problem will persist. Some of the more common CFCs have life expectancies of between 75 and 110 years, and the chlorine catalyst in the stratosphere can also be quite long-lived.

The estimated background level of chlorine in the atmosphere, derived from natural sources such as volcanoes, is about 0.6 ppb (parts per billion). Currently, due to human releases of chlorine-bearing chemicals like CFCs, the concentration of chlorine is about 3.5 ppb, and this number is increasing at a rate of about 5% a year.

Assuming that CFC production is phased out by the year 1998 (or 2008 in the case of some developing countries), atmospheric chlorine concentrations are still expected to reach 4.1 ppb by the end of the twentieth century.

Scientists estimate that the ozone layer will continue to be depleted until at least 2050, resulting in ozone losses of as high as 10 to 30% over the northern latitudes where most of the world’s population resides. During the latter half of the next century, the ozone may start to build up again, but measurable amounts of CFCs will continue to reside in the atmosphere well into the twenty-fourth century.

Thus, even if the 1990 and 1992 agreements are upheld by all nations (perhaps an overly optimistic assumption), the Earth will be subjected to an increasingly thin ozone layer for decades to come

Climate Change:

Atmospheric circulation, which ultimately causes what we see as weather (in the short term) and climate (in the longer term), is caused by the differential heating of air masses on the Earth’s surface. Although establishing the exact effects global warming will have on these patterns is extremely difficult, some educated predictions can be ventured.

As more heat is retained in the system, more air will move across the Earth’s surface producing winds, clashing warm and cold fronts, and generally more violent weather conditions. Hurricanes, tornadoes, and other dangerous storms will increase in intensity. Some researchers attribute the record number of extremely damaging storms in the last decade to global warming.

Global warming will also dramatically change overall climatic patterns. With increased warming, evaporation from the oceans and other large water masses may increase, which will lead to higher levels of precipitation. But the increased precipitation will not necessarily occur where it falls now-with the changing air currents, the areas of rainfall will be displaced.

The American Midwest, often referred to as the “breadbasket” of America (and the world), may experience such intense droughts that it will become a desert. The rain that would have fallen in this area may well be pushed north into Canada.

Rainfall may also shift from one season to another; some agricultural regions may receive more rain on average than at present, but the bulk of it will come during the winter months when it is of little use for crops.

Changing rainfall patterns, coupled with the generally more violent weather, will cause increasing incidences of flash floods. Ironically some areas will experience droughts and floods simultaneously; during the height of a drought, a violent cloudburst will cause rivers to swell and flood, but it will not replenish reservoirs, which require gentle, protracted rains in order to recharge.