Clouded AtmosphereThe concentration of the atmosphere’s main greenhouse gases specifically, carbondioxide, methane, nitrous oxide, and water vapor, have increased significantly during theindustrial age. These high concentrations are predicted to continue in the atmosphere forthousands of years to come. This increase in specially carbon dioxide, increases theinfrared energy taken in by the atmosphere, and warming the earth’s surface. The Globalmean temperature over the past 150 years has risen between 0.
3 degrees C and 0. 6degrees C. Climate changes that have been predicted are based on the continual rise inGreen House Gases. These changes include changes in: increase in mean surface airtemperature, increase in global mean rates of precipitation and evaporation, rising sealevel, and changes in the biosphere. There are many causes to the rise in Green House Gases in the atmosphere. Therise in carbon dioxide in the atmosphere is largely related to the combustion of fossil fuelsand cement production (Hansen).
The increase in methane is do to rice cultivation, animalhusbandry, biomass burning, and landfills (Kattenberg). Nitrous oxide is on the risebecause of industrial sources like adipic acid and nitric acid production (Kattenberg). Other gases not mentioned above that have a small impact on the Green House Gasproposed problem, is CFC-11 and CFC-12, these Gases are know to the public as being abig source of warming, although catalyzing decomposition of stratospheric ozone, theydo not pose a great threat. Since the public was notified of these compounds inrefrigerants, spray propellants, and foam blowing; the atmospheric concentrations havedecreased greatly (Prather). The danger that all these Green House Gases put to the atmosphere is the increasein the infrared energy absorbed by the atmosphere.
This extra energy absorbed althoughthought to only warm the earth also has a cooling tendency on the stratosphere (Peixotoand Oort). The affect the radiation has by this increase of Green House Gasesconcentration is also known as Infrared Flux at the tropopause (Wang). The modelsused to predict this information can also closely mimic the other layers of the atmosphereas well as the surface. Worldwide temperature measurements are carefully taken withmany variables in mind. Such variables would be urbanization of a region, aerosols,precipitation, and changes in temperature and clouds (Hansen).
Usually the temperature isthe first variable that is considered when assessments of the world climate change aretaken, it is also very important to consider other data that is part of the climate systemalong 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 measurementsof the mass of valley glaciers and ice caps. By looking at this material for the past 600years it has been determined that the warming in the twentieth century is greater over thistime period (Briffa). From paleoclimate studies it has been concluded that the Earth’s climate has beenaltered by more than just Green House Gases, but Inorder to find the effects of the GreenHouse Gases specifically, a study of records from the periods when the changes in theatmospheric carbon dioxide were much larger than those of our century. Large naturalvariation in the atmosphere’s carbon dioxide were found in the observation and analysis ofgas bubbles trapped in glacier ice cores, are correlated with glacial (ice age) andinterglacial climate change of the latest Pleistocene and Holocene epochs. These glacialperiods are associated with low carbon dioxide concentrations, and the interglacial periodswith 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 inGreen House Gases are: increase in mean surface air temperature, increase in global meanrates of precipitation and evaporation, rising of sea levels. An increase in the surface airtemperature would cause rates of evaporation to increase, causing the water vapor in theair to rise. The positive feedback to the surface temperature increase is that is will lead toa more intense hydrological cycle, with more precipitation events (Kattenberg). Anotherpossible consequence of greenhouse gas induced climate change is elevated sea levels.
The main cause for sea level fluctuation is due to thermal expansion and the melting ofglaciers, both are responses to higher air temperatures. Measurements taken from 93′ to98′ indicate a melt rate from Greenland’s ice sheet of 1 meter a year (Krabill). There havebeen 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 scientistpredict the climate change if the Green House Gases continue to rise at a steady rate. Although scientist are fairly confident in these models there is room for error in thesemodels.
Despite the gains there are a number of features of the climate system that arestill crudely represented in climate models. The models are restricted in their ability toaccurately represent terrain effects and to simulate processes that occur on a smaller scale. Other shortcomings in the climate models is their inability to actually portray the effects ofaerosols, precipitation, and clouds and changes in solar irradiance. For these and otherreasons there remains scientific uncertainties in model predictions, including uncertaintiesin the predictions of local effects of climate change, occurrence of extreme weatherevents, effects of aerosols, changes in clouds, shifts in precipitation, and even changes inocean circulation (Hansen).
Aerosols are a big concern for model analysts, because aerosols are a principlesource of uncertainty in modeling climate changes during the industrial period. Aerosolsscatter and absorb short wave (solar) radiation and modify the reflectivity of clouds. Botheffects are thought to decrease the abortion of short wave radiation by the Earth, coolingthe 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 theclimate is not yet know, or predicted. So many variables make up the atmosphere and it’sclimate, no model can accurately predict the future. Natural Earth warmers like watervapor and clouds also contribute to the warming trend.
The Earth’s records of ice agesand tree rings can only paint a very small piece of this huge picture. scientist are at adisadvantage because they are not able to see the Earth’s full past, as an instructor of mineonce said- they cannot predict the future of climate patterns when they have only beenstudding the atmosphere for the last 100 years. Science
