Is the humankind responsible for global warming?
The Earth climate is changing sweepingly. Fourteen out of last 17 years turned out to be the warmest in two and half centuries. According to the most pessimistic estimates, by mid next century further warming will cause loss of more than 1 trillion dollars or 10% of the world gross product. The climate change results from interaction of many natural and human-related factors. The most important of them on the time scale less than thousand years are the following:
1. concentration of greenhouse atmospheric gases ;
2. concentration of troposphere aerosols (sulfuric acid or sulfate aerosols, formed by interaction of sulfuric oxides and atmospheric water vapors);
3. The solar constant - thermal flow arriving from the Sun to the external border of troposphere;
4. volcanic activity, determining the degree of stratosphere satiation by aerosols of sulfuric acid;
5. non-periodic fluctuations in the system atmosphere-ocean – repeating at irregular time periods changes of water temperature in the Pacific Ocean (El Nino events);
6. parameters of the Earth orbit (eccentricity, precision, and the Earth axis angle to obliquity of ecliptic).
Changes of the first two factors during last 200 years are determined by human activity, but the rest of them depend on natural causes. According to the modern concepts, ÑÎ2 concentration is the most important greenhouse gas, directly related to the intensity of consumption of organic fuel, whose burning provides 80% of its supply in the atmosphere. According to the given estimates, by mid XXIst century energy consumption will stabilize and begin to decrease slowly.
Accordingly, it is expected that the concentration of atmospheric ÑÎ2 will constitute around 450 volumetric parts per million by the end of the next century. It would exceed the level of 1800 by 65%, but still be lower than the critical value of 560 million-1.
Concentration of other greenhouse gases - CH4 and N2O – should stabilize by the end of the next century at the level of 2.5 mln-1 and 0.37 million-1 correspondingly, that is, it will exceed the current level only by 20%.
Their concentration is determined by natural and antropogenic causes.
Chlorofluorocarbons (CFCs) have purely industrial origin. By the end of XXIst century, the concentration of Chlorofluorocarbons (CFCs) and their substitutes should not exceed 1.5 billion-1, that can give 10% of their total contribution into the greenhouse effect.
The concentration of troposphere aerosol is determined mainly by concentration of SO2 that has 60% of antropogenic origin. Presently, emission of sulfur and concentration of troposphere aerosol stabilized, and supposedly it will start to decrease after the year of 2030. The effect of sulfate aerosol on climate is opposite to that of greenhouse gas accumulation. Growth of its concentration in troposphere would increase reflection of the sun radiation and would result in climate cooling. Decrease of its concentration will have the opposite effect.
Superposition of several solar activity trends gives its stable maximum that will continue until 2010 and will be replaced by deep minimum after that. Minimum estimated decline of solar constant relative to the current level will be 0.4%, that is, it would be quite enough to decrease average global temperature by 0.5-0.6 OÑ.
The analysis of data for several centuries shows the inverse correlation between sun activity and frequency of volcanic eruptions. The mechanism of this connection is not quite clear. From the point of view of their effects on the climate, these factors amplify each other. Decrease of the Sun activity leads to decrease of average Earth temperature and at the same time, promotes volcanic activity, which, in turn, results in decreased solar radiation at the planet surface.
Autofluctuations in the atmosphere-ocean system lend themselves bad to long-term prognosis. It is expected that frequency of El Nino events will decrease significantly in the XXIst century.
When compared with all mentioned factors, Earth orbit parameter change acts on much larger time scale. Currently, the total effect of the orbit parameters change leads to slow decrease of the average global temperature at the rate of 0.04 oÑ per century.
Thus, the total impact of human activity on change of the Earth average global temperature is comparable with the total contribution of natural factors, but it acts mainly in the opposite direction. The trend of climate warming will continue throughout the XXIst century and the average tem-perature growth rate will be 1.2 oÑ per century. Emission of ÑÎ2 is responsible for 0.3 oC that is comparable to the level of natural year to year climatic fluctuations.
Artificial reduction by political regulative methods or limitation of ÑÎ2 emission under current conditions would mean reduction of energy consumption. It will insignificantly affect living standards
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