The concentration of the atmosphere’s main greenhouse gases specifically, carbon dioxide, methane, nitrous oxide, and water vapor, have increased significantly during the industrial age. These high concentrations are predicted to continue in the atmosphere for thousands of years to come. This increase especially carbon dioxide, increases the infrared energy taken in by the atmosphere, and warfare the earth’s surface. The Global mean temperature over the past 150 years has risen between 0.3 degrees C and 0.6 degrees C. Climate changes that have been predicted are based on the continual rise in Green House Gases.
These changes include changes in can decrease in mean surface air temperature, an increase in global mean rates of precipitation and evaporation, rising sea level, and changes in the biosphere.
There are many causes of the rise in Green House Gases in the atmosphere. The rise in carbon dioxide in the atmosphere is largely related to the combustion of fossil fuels and cement production (Hansen). The increase in methane is due to rice cultivation, animal husbandry, biomass burning, and landfills (Kattenberg).
Nitrous oxide is on the rise because of industrial sources like adipic acid and nitric acid production (Kattenberg).
Other gases not mentioned above that have a small impact o,n the Green House Gas proposed problem, are CFC-11 and CFC-12, these Gasesare is known to the public as being a big source of warming, although catalyzing the decomposition of stratospheric ozone, they do not pose a great threat. Since the public was notified of these compounds in refrigerants, spray propellants, and foam blowing; the atmospheric concentrations have decreased greatly (Prather).
The danger that all these Green House Gases put to the atmosphere is the increase in the infrared energy absorbed by the atmosphere. This extra energy absorbed although thought to only warm the earth also has a cooling tendency on the stratosphere (Peixoto and Oort). The effect the radiation has by this increase Green House Gases concentration is also known as Infrared Flux at the tropopause (Wang). The models used to predict this information can also closely mimic the other layers of the atmosphere as well as the surface. Worldwide temperature measurements are carefully taken with many variables in mind. Such variables would be urbanization of a region, aerosols, precipitation, and changes in temperature and clouds (Hansen). Usually, the temperature is the first variable that is considered when assessments of the world climate change are taken, it is also very important to consider other data that is part of the climate system along the line of time and space. Some other sources of information are tree rings, borehole temperature measurements in the soil, permafrost, and ice sheets, and measurements of the mass of valley glaciers and ice caps. By looking at this material for the past 600 years it has been determined that the warming in the twentieth century is greater over this period (Briffa).
From paleoclimate studies, it has been concluded that the Earth’s climate has been altered by more than just Green House Gases, but Inorder to find the effects of the Green House Gases specifically, a study of records from the periods when the changes in the atmospheric carbon dioxide were much larger than those of our century. Large natural variation in the atmosphere’s carbon dioxide was found in the observation and analysis of gas bubbles trapped in glacier ice cores, which are correlated with glacial (ice age) and interglacial climate change of the latest Pleistocene and Holocene epochs. These glacial periods are associated with low carbon dioxide concentration and interglacial periods with high concentrations. When looking at methane concentrations within these cores, there was a similar correlation (Chappellaz).
Some of the predicted changes to the Earth’s climate due to this continual rise in Green House Gases are an increase in mean surface air temperature e, an increase in global mean rates of precipitation and evaporation, rising in the sea levels. An increase in the surface air temperature would cause rates of evaporation to increase, causing the water vapor in the air to rise. The positive feedback to the surface temperature increase is that it will lead to a more intense hydrological cycle, with more precipitation events (Kattenberg). Another possible consequence of greenhouse gas-induced climate change is elevated sea levels.
The main cause of sea level fluctuation is due to thermal expansion and the melting of glaciers, both are responses to higher air temperatures. Measurements taken from 93′ to 98′ indicate a melt rate from Greenland’s ice sheet of 1 meter a year (Krabill). There have been measurements of the sea levels also, they indicate a rise of about 10 – 25 cm a year (Douglas).
All of these predictions were made by constructing models that help scientists predict climate change if the Green House Gases continue to rise at a steady rate.
Although scientists are fairly confident in these models there is room for error. Despite the gains, there are several features of the climate system that are still crudely represented in climate models. The models are restricted in their ability to accurately represent terrain effects and to simulate processes that occur on a smaller scale.
Other shortcomings in the climate models are their inability to portray the effects of aerosols, precipitation, clouds, and, changes in solar irradiance. For these and other reasons there remains scientific uncertainties in model predictions, including uncertainties in the predictions of local effects of climate change, the occurrence of extreme weather events, effects of aerosols, changes in clouds, shifts in precipitation, and even changes in ocean circulation (Hansen).
Aerosols are a big concern for model analysts because aerosols are a principal source of uncertainty in modeling climate changes during the industrial period. Aerosols scatter and absorb short wave (solar) radiation and modify the reflectivity of clouds. Both effects are thought to decrease the abortion of short wave radiation by the Earth, cooling the climate, even though the troposphere aerosols only last a day in the atmosphere (Charlson).
Green House Gases are related to the warming of the Earth, but the future of the climate is not yet known or predicted. So many variables make up the atmosphere and its climate, that no model can accurately predict the future. Natural Earth warmers like water vapor and clouds also contribute to the warming trend. The Earth’s records of ice ages and tree rings can only paint a very small piece of this huge picture. Scientists are at a disadvantage because they are not able to see the Earth’s full past, as an instructor of mine once said- they cannot predict the future of climate patterns when they have only been studying the atmosphere for the last 100 years.