Global dimming is a recently recognized phenomenon of the gradual decrease duration of the sunlight and direct radiation entering the Earth. This phenomenon has been acknowledged since the 1950’s as scientists have been taking measurements of the amount of time the Earth has been exposed to the Sun and its elements. The resultant trends have been that the duration of Sun exposure the Earth receives has been decreasing systematically since the initiation of the research.
Mostly the causes for the reduction in the heat reaching the earth from the sun have been determined as the increase in the pollutants in the atmosphere. These pollutants have changed the properties of the clouds and as a result most of the sunlight, radiation and heat from the sun are reflected from the water vapor in the air, back into space. Most of the harmful pollutants have been identified as sulfur dioxide, carbon dioxide, carbon monoxide, ash and soot.
The increase in the amount of black carbon in the air has also been a main contributor to the increase in global dimming. Aside form this Global dimming has also been attributed to interfering with the hydrological cycle. This is that due to global dimming, and the less exposure of the sun on the earth, the rate of water evaporation has also decreased which is resulting in a reverse effect that the water vapor on earth is decreasing resulting in severe draughts and extreme weather conditions. This has been deduced as one of the main reasons for the draughts taking place in the African and Central Australian region.
Global dimming is a reverse of the ‘Global Warming’ phenomena. In global warming the cloud cover combined with the pollutants and the CFC’s in the air trap the sun’s rays and radiation inside the earth (internal reflection). In global dimming however the sun’s rays, radiation and heat is reflected out back in to the space. As a result, the earth is due to become cooler with extreme temperatures both cold and hot. In the long run however, if the global dimming keeps up the earth will be pulled back into a second ice age as the temperature of the earth keeps on falling.
Causes of Global Dimming:
The main factors that have been contributing to the phenomenon f global dimming have been identified as:
The increase in the number of pollutants in the air which have led to increase in the pollutant water vapor and fumes in the air compared to the cloud structure.
The decreasing cloud structure has contributed to the reflection of suns rays back into space and therefore resulting in less heat entering the earth.
It is also presumed that global dimming has been aggravated by the presence of aerosol particles in the air which have been a major by product of human action and increased industrialization.
Consumption of fossil fuels, burning of crude oil and diesel are also large contributing factors for the increase in global dimming.
Incomplete burning of crude materials like hardwood and manure in developing countries and third world countries.
Due to the occurrence of global warming many developing and developed countries have established ‘carbon sinks’ to control their level of emissions,which are basically large storages of carbon monoxide produced and emitted by the industries which are further oxidized into carbon dioxide. These storages are then emptied when the carbon monoxide has finally been oxidized to carbon dioxide. The dumps are one of the main contributing factors towards global dimming as well as they emit a larger and more fluent flow of harmful gases into the air which becomes more concentrated with the pollutants.
Another surprising factor that is found to be contributing to the appearance of global dimming is the contrails produced by jets and airplanes flying in the sky. This factor was confirmed as a cause for global dimming in the events after the September 11 in 2001 when all the planes were grounded. Scientists took this opportunity to study the atmosphere and the temperatures and they noticed that the temperature increased throughout northern America by an average of 1 degree Celsius in this period, thus confirming the contrails from aviation jets as a major cause of global dimming as well.
Global dimming is not taking place entirely because of human actions. Natural disasters like volcanic eruptions have also contributed largely to global dimming as the ash and incomplete burnt minerals and elements from the earths crust result in the emission of oxides in the air. These then have the same effect on the earth’s atmosphere as the emission of pollutants. This cause has been supported by the research conducted after the volcano eruptions in Bali, Mexico and Columbia where following the volcanic eruptions the temperature dropped rapidly in the region. These pollutants and ash clouds emitted by volcanic eruption are large in scale but stay for only a small period of time. Also aside from this the volcanic activity is a rare occurrence and therefore not an immediate threat.
Effects of Global Dimming:
The most far-stretched conclusions that have been drawn from global dimming is that it may force the world into another ice-age in the future, whereby killing all the life form on earth. However as the time required and the process are very slow it will take quite a lot of time.
Due to the climatic changes it is believed that endangered animals and forests would be the first on Earth to get effected. In fact in areas like Greenland, Maldives and Africa the process has been started since the 1970’s
Currently global dimming has resulted in the decrease in the temperatures world wide. Studies dating back to 1960’s show that the temperature has decreased around the world in ranging from 6 percent to 1 percent.
Studies have also shown that the temperatures have dropped on a regional scale. More precisely countries located below the pollution, sulfur and carbon monoxide emitting countries have shown readings of temperatures dropping by 10% while the rest of the world seems to be getting warmer due to global warming.
Global dimming has been occurring simultaneous to the global warming and often due to the same reasons. However predictions for the future increase in temperatures, which have predicted to be at 5 degrees in the future, have not been made keeping the effects of the global dimming in perspective. As a result the intensity and the extent of the effects of global warming have been hidden by global dimming and the scales can be tipped at any end by the slightest atmospheric changes.
The catch 22 with global warming and global dimming is that they pose two extreme opposite threats to the planet.
The problem that is being faced by most scientists and governments in the world is that trying to implement measures to reduce global warming will simply help increase the causes and the chances of global dimming and similarly controlling the factors which effect global dimming are only going to lead to increasing the temperatures on earth on a very rapid scale, therefore resulting in global warming.
In 2003 Europe implemented measures to clean up the atmosphere of the pollutants by restricting the emission of these pollutants. However these steps were taken without addressing the emissions of the greenhouse gases. As a result global dimming for the period was reduced in the region but the temperatures in the region. The effects of these measures are cited below as:
§ The severity of droughts in Sahel was decreased
§ The shortage pf rainfalls in Sahel also decreased
§ The European heat wave of 2003 occurred
§ Thousands of people in France died in the European heat wave
§ Portugal faced extensive forest fires
Another study suggested that the if global dimming was to be addressed without decreasing the emissions of the Chloro-Floro-Carbons (CFC’s) then the global warming would be simply more aggravated and at a much higher rate with the possible effects predicted as:
· The increasing rate of melting ice in Greenland which would be increasing the sea levels around the world
· An increase in the number of glaciers being dislodged from the mainland in Green land which would disrupt the ocean traffic in the Atlantic Ocean. Aside from this it could also possibly raise the wave level in the region as well.
· The increasing sea levels would result in lost land especially in the coastal areas around the world.
· Major cities like Venice, which are already feeling the effects of global warming, might get largely affected by the increase in the water levels in the next30 years.
· Major landmarks and cities of historical and archeological prominence will be lost to man.
· The tropical rainforests would decrease which would result in an increase in the dry and deserted land in the region. This would increase the chance and dangers of forest fires etc.
Aside from this with more countries pushing for and implementing ‘carbon sinks’ to control their level of emissions adverse effects which would actually aggravate global warming could take place. The resultant effects could be like the following:
· Soil erosion will occur
· Irregular rainfalls would be predominant
· Vegetation will die off
· A ‘Saharan’ climate can become a characteristic of places like England and France
· The countries in the world which face hot climates already would be facing hotter climates in the future which would enable human inhabitance impossible
· There would also be resultant large stores of greenhouse gases on earth like methane hydrate which is at the moment found at the bottom of the sea beds. This specific gas has the characteristic of being almost eight times stronger than carbon dioxide in its green house effects
The Russian Scientist Mikhail Budyko was the person to identify that aerosols could be used to stop the effects of global warming if an emergency so arrived. He went on to say that “if global warming became a problem, we could cool down the planet by burning sulfur in the stratosphere, which would create a haze.” (Budyko, 1974) However if we used aerosols or sulfates for solving the problem we would still be facing others like:
Sulfates would eventually dissolve in water in the air to create acid rain, which is caused by usually incomplete compounds like sulfur oxides
The carbon black will result in health problems for humans and animals.
Plant and vegetation will also suffer with extra sulfur in the air. Also the acid rain will probably destroy the forests.
Using sulfates we will be promoting global dimming which would be creating further nuances like irregular rainfall and disruption of the evaporation cycle.
There might be draughts or excess rainfalls which might lead in natural disasters like massive floods.
Even if we use aerosols to combat the effects of global warming they would not last for long as aerosols have a very small life span
Other more indirect effects of global dimming may include the following:
Some countries might benefit from global dimming while other countries might have to suffer due to it.
The growth of the economies around the world will be effected and decrease by 20% on average.
There will be reduction in crop yields and therefore the agriculture sector in all economies will fail due to failure of the crops to generate and grow in the parse climatic conditions.
The most effected region from the agricultural decline point of view would be Africa. This is mostly due to the fact that most of the countries in Africa have their economies based on agriculture. What adds more to this regions vulnerability is the fact that it is situated right below Europe which has, overall, large amounts of greenhouse gas emissions and pollutants being emitted into the atmosphere.
The insurance industry is going to suffer a probable crash as the number of insurance claims will increase as the number natural disasters like hurricanes, famines, draught and infrastructure damage start talking place.
The value of properties will increase, especially those in the coastal regions, as it would become more difficult and costly to maintain them given the harsh climatic conditions.
The transport sector will be largely effected as well as the infrastructure like roads, railways, airport runways, pipelines etc. need to be maintained in accordance with the climatic effects on them. As with global dimming the climatic effects would be very harsh, it would also become costly and difficult to maintain the infrastructure in this industry. There would be much permanent damage in the areas where permafrost occurrence is already predominant.
As in the earlier centuries the main way to travel and perform trade was through ships and oceans almost all of the industrial and economic centers of the world are in cities which are either on or near the coastlines. These areas would be receiving massive damage due to the climatic conditions and there would be massive loss of information worldwide.
As some regions in the world become unfit for human inhabitance there will be an increase in the number of the planets population migrating to safer and habitable regions. Some of the islands and mountain regions might need to be evacuated.
Another interesting effect which is predominant even now due to the increase in the levels of carbon and its compounds in the air has been that the forests of the world, especially those in the tropical regions, have gotten more wooded or thicker. The reasons for this have not been ascertained till now but this effect is being attributed to the increase in the carbon dioxide in the air
Another thing is that as plants photosynthesize at night and with global dimming they would photosynthesize more affluently therefore they might grow faster. However if there are any plants which are already suffering due to insufficient water or lack of nutrients, they will suffer even more so due to global dimming. This pattern is already apparent in Australia.
Plants which grow on high altitudes where the light is already insufficient will also find it hard survive due to global dimming.
Therefore the only option that we do have is to stop the emission of greenhouse gases as well as other impurities and particles in the atmosphere.
Global Dimming and the Hydrological Cycle:
The hydrological cycle is the process of sun heating the water in the oceans so that the water starts evaporating in the form of water vapor. This water vapor then rises in the air until it reaches a certain height where the air is cooler. Here it starts to cool and condense. When the water vapor starts condensing and heavy droplets of water start forming they fall on the land back again in the form of rain.
It has been seen that due to global dimming the hydrological cycle tends to get disrupted as when global dimming takes place the earth starts receiving less heat and radiation from the sun. As a result the water in the oceans does not evaporate at the rate that it should. This decreases the amount of water vapor in the air. As the water vapor in the air maintains the climatic condition and provides a humid environment for the plants to survive, this would eventually be changed due to global dimming. As the percentage of water vapor content in the air would decrease this would result in infrequent or almost no rainfall making the dry areas of the earth drier while bringing draught to other regions. The lack of rainfall would also result in the elimination of vegetation and flora and fauna from some regions as well.
The main cause of the disruption to the hydrological cycle due to global dimming has been established as the aerosol emissions, soot, ash and other pollutants. Climate charts and records from the 1970s and the 1980s also suggest that the denied occurrence of the monsoon rains in the Sahara region in the states specific period were a possible result of global dimming. Aside from this the draughts and famines in Sahel have also been attributed to global dimming. The recent hurricanes that affected the Florida and Houston region of the United States, Hurricane Rita and Hurricane Katrina, have also been said to have been cause due to these irregular climatic changes.
‘Moon Lit’ Project as a solution to Global Dimming:
Richard Brook Cathcart of California has come up with a suggestion of an alternate source of lighting the earth. He mentions that Earth can be lighted by the Moon, or rather by reflecting the light of the sun which reaches the moon onto the earth.
“Artificial illumination of the inhabited Earth can be instituted using Moon-based mirrors reflecting sunlight and/or by a substituted “sunlight” source made to glow by fusion-powered electrical generators fueled with Moon-mined 3He or by enrobing the Moon’s crust with photovoltaic panels. Curative macro-engineering may be needed if Earth undergoes a natural “global dimming”, a regionalized or local catastrophic haze, and even a major macro-project’s failure or infrastructure breakdown. Photonic-crystal filaments lighting may also be applicable, playing an important future role in ongoing “anti-global dimming” R&D – the ‘Moon-as-Disco Ball’ solution.” (Cathcart, “Moon Lit Earth”)
Global Dimming as an Issue for the Masses:
‘Nova: Dimming the Sun’ is a documentary movie which has received the EarthWatch Award and the CINE Golden Eagle Award at the Environmental Film Festival which was held in association with the National Geographic Society in March 2007. the Movie has been able to explore the positive impacts of the air quality regulations which have resulted in slowing the global dimming by reducing the number of aerosols released in the air since the 1990s. The movie at the same time attempts to reveal the conflicting relationship between global warming and global dimming and what possible solution can be taken to relatively slow both of them and encourage longevity of life on Earth.
Global Dimming and Research:
Mikhail Ivanovich Budyko is a Russian scientist who has extensively worked on the climatic conditions and the temperatures of the earth. He was the person who suggested I the 1960s that sulfates could be used to stop global warming. However using sulfates resulted in increase of a chance of global dimming there developed a theory. The theory “worked with simple two-dimensional energy-balance climate models to investigate the reflectivity of ice” (Budkyo, 1960). In his research he was able to determine that the ice reflection created a positive feedback loop for the temperature on the earth. As a result when there was ice on earth, more of the suns heat and radiation is reflected back into the space resulting in making the earth a cooler place with larger amounts of snow covered regions.
Other studies by Rasool and Schneider have also shown that global dimming could be highly aggravated by volcanic eruptions. As a result a large number of volcanic activity resulting in volcanic eruptions can lead to taking the Earth back to the Ice Age.
Rasool, Steven and Scheider’s research states that “Effects on the global temperature of large increases in carbon dioxide and aerosol densities in the atmosphere of Earth have been computed. It is found that, although the addition of carbon dioxide in the atmosphere does increase the surface temperature, the rate of temperature increase diminishes with increasing carbon dioxide in the atmosphere. For aerosols, however, the net effect of increase in density is to reduce the surface temperature of Earth. Because of the exponential dependence of the backscattering, the rate of temperature decrease is augmented with increasing aerosol content. An increase by only a factor of 4 in global aerosol background concentration may be sufficient to reduce the surface temperature by as much as 3.5 ° K. If sustained over a period of several years, such a temperature decrease over the whole globe is believed to be sufficient to trigger an ice age.” (Rasool, Schneider, Steven, 1971)
H.C. Power from the Department of Geography of the University of California conducted a research on the trends concerning the solar radiation over Germany and the participation of aerosols in the duration of sunshine received by the country. The research stated that diffusion has taken place in the strength of the rays of radiation that have been received by the various test station in Germany. For the purpose of this research tests were conducted in 13 and the result was a 2.7 percent reduction in the amount of radiation being received in those regions. Aside from this the study also showed that aerosols have a direct relationship with Global Dimming and as a result of increased aerosols in the air due to volcanic eruptions the temperature of the earth has started cooling in certain regions while it remains a steady rise in others. “Temporal and spatial variability in annually averaged global, diffuse, and horizontal direct irradiance has been evaluated at 13 stations in Germany, where the time series range between 11 and 48 years. Using a least-squares estimation method and a significance level of 95%, global irradiance has decreased significantly at two stations located in the southeast, and increased at four stations, three of which are in the southwest. The mean trend across these six stations is an increase in global irradiance of 1.94Wm_2 or 1.83% per decade” (Power, 2003)
Stanhill and Cohen conducted a research targeting the changes in the solar radiation in the United States in the last century. They supported their research with the official measurements for sunshine duration on earth. Their research showed that prior to the 1950s global warming and global dimming were both taking place, however global warming was more obvious as temperature increases in 27 sites were recorded compared with the temperature decreases in 21 sites. However after the 1950s the trend for the temperatures has been downhill and the temperatures have been steadily decreasing at small creeping average. This has depicted that global dimming is becoming more of an imminent problem for us in the future compared to the global warming. “There was little evidence for a large or significant influence of sunspot numbers on sunshine duration when lagged values within the 11-yr solar cycle were correlated. The major volcanic eruptions occurring in America during 1902 and 1984 were associated with reduced annual sunshine duration both in the year of the eruption and to a lesser extent in the two subsequent years. The decrease was larger than, but consistent with, that predicted from the increased load of volcanic aerosols found during these periods. It is concluded from this analysis of the U.S. sunshine duration database that measurements of SS do not support the growing number of studies showing significant reductions in Eg? in the second half of the previous century.” (Stanhill, Cohen, 2004)
Another research, this one by Stotts, Huntingford, Boucher, Betts, Cox, and Gedney was focused towards measuring the effect of carbon dioxide on the river runoff records. This study showed that even with increased consumption of water by people, rivers have been flooding. The result of this has been attributed mainly to deforestation and soil erosion which has left the banks of the rivers weak and unprotected. However the study showed that there are more elements effecting this issue than the ones already mentioned. The dual effect of global warming and global dimming has also been playing a part in increasing the number of flood occurrences in the Asia region especially in the monsoon season. The study states that “an overall increase in atmospheric aerosol concentration over the past century appears to have reduced the amount of solar radiation reaching the land surface (so-called ‘solar dimming’), and may have led to reductions in open-pan evaporation.” (Stotts et al, 2006)
Although some of these researches provide substantial evidence for the occurrence global dimming, the exact reasons for the aggregated effects of dimming while global warming is taking place are still unknown. Further research needs to be conducted to resolve these issues. However these research do provide evidence as to why countries in Asia, Africa and Austral-Asia and Europe are being effected by global warming while developed countries in Northern America and Europe are recording and displaying decreasing temperatures due to global dimming which is in contradiction with the global warming predominant in the rest of the world.
McFedries, Paul., “Changing Climate, Changing Language.” IEEE Spectrum, Vol.43, 2006. Available at: <http://web.ebscohost.com/bsi/detail?vid=1&hid=19&sid=c1334f61-d57f-4aac-a49a-26c95d0ec03a%40sessionmgr7>
“Sunny Side Up”, Economist, Vol. 375, 2005. Available at: <http://web.ebscohost.com/bsi/detail?vid=1&hid=19&sid=cab7d573-bbbb-44e6-8e57-76f9a2107e5b%40sessionmgr7>
Foukal, Peter., North Gerald., Wigley Tom., “A Stellar View on Solar Variations and Climate” Science, Vol. 306, 2004. Available at: <http://web.ebscohost.com/ehost/detail?vid=1&hid=106&sid=ce3a95ec-71e0-4243-9e91-ba5d948824a9%40sessionmgr104>
J.T. Houghton et al., Eds., “Climate Change 2001: The Scientific Basis” Cambridge Univ. Press, Cambridge, 2001.
Budyko, M.I., “The Effect of Solar Radiation Variations on the Climate of the Earth”, 1969 Available at: <http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=A7021919AH&q=&uid=790417110&setcookie=yes>
Rasool, Ichtiaque, S. and Schneider, Stephen H., “Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate”, Science, 1971. Available at: <http://www.sciencemag.org/cgi/content/abstract/173/3992/138>
Sington, David, “Global Dimming”, Available at: <http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_prog_summary.shtml>
Adam, David, “Goodbye Sunshine”, The Guardian, 18 December, 2003. Available at: <http://www.guardian.co.uk/life/feature/story/0,13026,1108853,00.html>
Brook Cathcart, Richard, “Moon-lit Earth: A ‘Global Dimming’ Macro Project Cure”, Available at: <http://www.daviddarling.info/encyclopedia/M/Moon_mirror_Cathcart.html>
H. C. Power, “Trends in Solar Radiation over Germany and n Assessment of the Role of Aerosols and Sunshine Duration”, Theoretical & Applied Climatology, Vol. 76, 2003
Bartlett, Marshall G., Chapman, David S., Harris, Robert N., “A Decade of Ground–Air Temperature Tracking at Emigrant Pass Observatory”, Journal of Climate, Vol.19, 2006. Available at: <http://web.ebscohost.com/ehost/pdf?vid=2&hid=104&sid=03363f23-e860-43d1-b118-c73d18658c73%40SRCSM2>
Gedney, N., Cox, P. M., Betts, R. A., Boucher, O., Huntingford, C., Stott, P. A., “Detection of a Direct Carbon Dioxide Effect in Continental River Runoff.”, Nature, Vol. 439, 2006. Available at: <http://web.ebscohost.com/ehost/pdf?vid=2&hid=120&sid=7cc021f4-eb30-4010-bc16-75e70a7c861e%40sessionmgr102>
Stanhill, Gerald, Cohen, Shabtai, “Solar Radiation Changes in the United States during the Twentieth Century: Evidence from Sunshine Duration Measurements.”, Journal of Climate, Vol.18, 2005, Available at: <http://web.ebscohost.com/ehost/pdf?vid=2&hid=101&sid=296b093b-d60f-4543-b182-b560c2a0cc81%40sessionmgr108>