Clouded Atmosphere Essay, Research Paper

Clouded Atmosphere

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 in specially carbon dioxide, increases the

infrared energy taken in by the atmosphere, and warming 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: increase in mean surface air

temperature, increase in global mean rates of precipitation and evaporation, rising sea

level, and changes in the biosphere.

There are many causes to 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 do 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 on the Green House Gas

proposed problem, is CFC-11 and CFC-12, these Gases are know to the public as being a

big source of warming, although catalyzing 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 affect the radiation has by this increase of 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, bore

hole 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

time 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 were found in the observation and analysis of

gas bubbles trapped in glacier ice cores, 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 concentrations, and the 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: increase in mean surface air temperature, increase in global mean

rates of precipitation and evaporation, rising of 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 is 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 for 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 scientist

predict 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 these

models. Despite the gains there are a number of 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 is their inability to actually portray the effects of

aerosols, precipitation, and 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, 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 principle

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 know, or predicted. So many variables make up the atmosphere and it’s

climate, 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. scientist 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

studding the atmosphere for the last 100 years.

Bibliography

References

Briffa, K. R. “Influence of volcanic eruptions on Northern Hemisphere summer

temperature over past 600 years.” Nature, 393, 1998.

Chappellaz, J. “Ice- core record of atmospheric methane over the past 160,000 years.”

Nature, 345, 1990.

Charlson, R. J. “Climate forcing by anthropogenic aerosols.” Science 255, 1992.

Douglas B. C. Global sea level rise, J. geophys. Res., 96 (C4), 6981-6992, 1991.

Hansen, J. E. (1998). Climate forcings in the industrial era. Livermore: Willams Press.

Kattenberg, A. (1996). Climate Change 1995: The Science of Climate Change.Cambridge:

Cambridge University Press.

Krabill. W. “Rapid thinning of parts of the southern Greenland ice sheet.” Science 283,

1999.

Peixoto, J. P., and A. H. Oort (1992). Physics of Climate. New York: American Institute

of Physics.

Prather, M. P. “The ozone layer: The road not taken.” Nature 381, 1996.

Wang, W. C. “Inadequacy of affective CO2 as a proxy in simulating the greenhouse effect

of other radiatively active gases.” Nature 350, 1991.