Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth's surface that was observed for several decades after the start of systematic measurements in 1950s. Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in Air pollution is the human introduction into the atmosphere of Chemicals Particulate matter, or Biological materials that cause harm or discomfort Acid rain is Rain or any other form of precipitation that is unusually Acidic It has harmful effects on plants aquatic animals and infastructure The Air Quality Index ( AQI) is a standardized indicator of the Air Quality in a given location Atmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane Global warming is the increase in the average measured temperature of the Haze is traditionally an atmospheric phenomenon where dust smoke and other dry particles obscure the clarity of the sky Indoor Air Quality (IAQ deals with the content of interior air that could affect health and comfort of building occupants Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas Smog is a kind of Air pollution; the word "smog" is a Portmanteau of Smoke and Fog. Water pollution is the contamination of Water bodies such as Lakes Rivers Oceans and Groundwater caused by human activities Eutrophication is an increase in chemical Nutrients -- typically compounds containing Nitrogen or Phosphorus -- in an Ecosystem, and may occur For other uses of the term "hypoxia" see Hypoxia. Hypoxia or oxygen depletion is a phenomenon that occurs in aquatic environments Marine pollution is the harmful effect caused by the entry into the ocean of chemicals particles, or Plastic debris. For the fictional character see Oil Slick (Transformers. An oil spill is the release of a Liquid Petroleum Hydrocarbon into Ship pollution is the pollution of air and Water by Shipping. Surface runoff is a term used to describe when soil is infiltrated to full capacity and excess Water, from Rain, Snowmelt, or other sources flows Thermal pollution is a Temperature change in natural bodies of water caused by human influence Distinguish from Wastwater (a lake in the Lake District in northwest England Waterborne diseases are caused by Pathogenic Microorganisms which are directly transmitted when contaminated Drinking water is consumed Water quality is the physical chemical and biological characteristics of Water in relationship to a set of standards Water stagnation occurs when Water stops flowing Stagnant water can be a major Environmental hazard. Soil contamination is caused by the presence of man-made chemicals or other alteration in the natural soil environment Bioremediation can be defined as any process that uses Microorganisms Fungi, green plants or their Enzymes to return the natural environment altered A herbicide is used to kill unwanted Plants Selective herbicides kill specific targets while leaving the desired Crop relatively unharmed A pesticide is a substance or mixture of substances used to kill a pest. Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment Actinides in the environment refer to the sources environmental behaviour and effects of Actinides in the environment. Environmental Radioactivity is the study of radioactive materials in the Human environment. Fission products are the atomic fragments left after a large nucleus fissions. Fallout is the residual radiation hazard from a Nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion Plutonium in the environment is an article which is part of the Actinides in the environment series Radiation poisoning, also called " radiation sickness " or a " creeping dose " is a form of damage to organ tissue due to excessive exposure to This is a subpage of Environmental radioactivity. Radium Radium in quack medicine See the story of Eben Byers for details of one very nasty case Uranium in the environment, this page is about the Science of Uranium in the environment and in animals (including humans Introduced species|Weed Invasive species is a phrase with several definitions Light pollution, also known as photopollution or luminous pollution, is excess or obtrusive Light created mainly by Humans Among other effects Noise pollution (or environmental noise) is displeasing human- or machine-created sound that disrupts the activity or balance of human or animal life Radio spectrum pollution is the straying of waves in the radio and Electromagnetic spectrums outside their allocations that cause problems for some activities Visual pollution is the term given to unattractive or unnatural (human-made visual elements of a vista a Landscape, or any other thing that a person might not want to For other similarly-named agreements see Montreal Convention (disambiguation. Protocol to the 1979 Convention on Long-Range Transboundary Air Pollution Concerning the Control of Emissions of Nitrogen Oxides or Their Transboundary Fluxes, opened for signature on The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing Greenhouse gases in an effort The Convention on Long-Range Transboundary Air Pollution, often abbreviated as Air Pollution or CLRTAP, is intended to protect the human environment against Air This is a list of environmental organizations. See also Environmental organization Intergovernmental organizations International organizations The Department for Environment Food and Rural Affairs ( Defra) is the United Kingdom government department responsible for environmental protection The Global Atmosphere Watch (GAW is a worldwide system established by the World Meteorological Organization a United Nations agency to monitor trends in the Greenpeace, originally known as the Greenpeace Foundation, was founded in Vancouver, British Columbia, Canada in 1972 The National Ambient Air Quality Standards (NAAQS are standards established by the United States Environmental Protection Agency that apply for outdoor Air Environmental science is the study of interactions among physical chemical and biological components of the environment. See also Nature The natural environment, commonly referred to simply as the environment, is a terminology that is comprised of all living and Irradiance, radiant emittance, and radiant exitance are Radiometry terms for the power of Electromagnetic radiation at a surface per unit EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 The effect varies by location, but worldwide it has been estimated to be of the order of a 4% reduction over the three decades from 1960–1990. However, since 1990, the trend has reversed. ^[1]

It is thought to have been caused by an increase in particulates such as sulphate aerosols in the atmosphere due to human action. Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas The switch from a "global dimming" trend to a "brightening" trend in 1990 happened just as global aerosol levels started to decline.

Global dimming has interfered with the hydrological cycle by reducing evaporation and may have reduced rainfall in some areas. The Earth 's Water is always in movement and the water cycle, also known as the hydrologic cycle, describes the continuous movement of water on above Global dimming also creates a cooling effect that may have partially masked the effect of greenhouse gases on global warming. Global cooling in general can refer to an overall cooling of the Earth. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared Global warming is the increase in the average measured temperature of the

Causes and effects

Further information: Albedo, irradiance, and insolation

It is thought that global dimming was probably due to the increased presence of aerosol particles in the atmosphere caused by human action. The albedo of an object is the extent to which it diffusely reflects light from the sun Irradiance, radiant emittance, and radiant exitance are Radiometry terms for the power of Electromagnetic radiation at a surface per unit Insolation is a measure of Solar radiation energy received on a given surface area in a given time Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five ^[2] Aerosols and other particulates absorb solar energy and reflect sunlight back into space. The pollutants can also become nuclei for cloud droplets. Cloud condensation nuclei or CCN s (also known as cloud seeds) are small particles (typically 0 Water droplets in clouds coalesce around the particles. A cloud is a visible mass of droplets or frozen crystals floating in the atmosphere above the surface of the Earth or another Planetary body ^[3] Increased pollution causes more particulates and thereby creates clouds consisting of a greater number of smaller droplets (that is, the same amount of water is spread over more droplets). The smaller droplets make clouds more reflective, so that more incoming sunlight is reflected back into space and less reaches the earth's surface. The albedo of an object is the extent to which it diffusely reflects light from the sun

Clouds intercept both heat from the sun and heat radiated from the Earth. Their effects are complex and vary in time, location, and altitude. Usually during the daytime the interception of sunlight predominates, giving a cooling effect; however, at night the re-radiation of heat to the Earth slows the Earth's heat loss.

Research

Further information: Climate model and pyranometer

Eastern China. This article is about the theories and mathematics of climate modeling A pyranometer is a type of Actinometer used to measure broadband Solar irradiance on a planar surface and is a sensor that is designed to measure the solar radiation China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National Dozens of fires burning on the surface (red dots) and a thick pall of smoke and haze (greyish pixels) filling the skies overhead. Photo taken by MODIS aboard NASA's Aqua satellite

In the late-1960s, Mikhail Ivanovich Budyko worked with simple two-dimensional energy-balance climate models to investigate the reflectivity of ice. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The 1960s decade refers to the years from the beginning of 1960 to the end of 1969 Mikhail Ivanovich Budyko (Михаил Иванович Будыко (born January 20 1920 Gomel, Belarus) is a Russian Climatologist and one ^[4] He found that the ice-albedo feedback created a positive feedback loop in the Earth's climate system. The more snow and ice, the more solar radiation is reflected back into space and hence the colder Earth grows and the more it snows. Other studies found that pollution or a volcano eruption could snap Earth into an ice age. ^[5][6]

In the mid-1980s, Atsumu Ohmura, a geography researcher at the Swiss Federal Institute of Technology, found that solar radiation striking the Earth's surface had declined by more than 10% over the three previous decades. The 1980s was the decade spanning from January 1 1980 to December 31 1989. is a Japanese Climatologist, known for his contributions to the theory of Global dimming. His findings are in apparent contradiction to global warming—the global temperature has steadily been going up. Global warming is the increase in the average measured temperature of the Less light reaching the earth would mean that it would have to cool. Ohmura published his findings "Secular variation of global radiation in Europe" in 1989. ^[7] This was soon followed by others. Viivi Russak in 1990 "Trends of solar radiation, cloudiness and atmospheric transparency during recent decades in Estonia",^[8] and Beate Liepert in 1994 "Solar radiation in Germany — Observed trends and an assessment of their causes". ^[9] Dimming has also been observed in sites all over the Former Soviet Union. ^[10] Gerry Stanhill who studied these declines worldwide in many papers (see references) coined the term "Global dimming". ^[11]

Golden Gate Bridge with California's characteristic brown cloud in the background — a likely contributor to global dimming. The Golden Gate Bridge is a suspension Bridge spanning the Golden Gate, the opening of the San Francisco Bay onto the Pacific Ocean California ( is a US state on the West Coast of the United States, along the Pacific Ocean.

Independent research in Israel and the Netherlands in the late 1980s showed an apparent reduction in the amount of sunlight,^[12] despite widespread evidence that the climate was actually becoming hotter. For a topic outline on this subject see List of basic Israel topics. The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands The rate of dimming varies around the world but is on average estimated at around 2–3% per decade. The trend reversed in the early 1990s. ^[1] It is difficult to make a precise measurement, due to the difficulty in accurately calibrating the instruments used, and the problem of spatial coverage. Calibration is the process of establishing the relationship between a measuring device and the units of measure Nonetheless, the effect is almost certainly present.

The effect (2–3%, as above) is due to changes within the Earth's atmosphere; the value of the solar radiation at the top of the atmosphere has not changed by more than a fraction of this amount. ^[13]

The effect varies greatly over the planet, but estimates of the terrestrial surface average value are:

• 5. 3% (9 W/m²); over 1958–85 (Stanhill and Moreshet, 1992)^[11]
• 2%/decade over 1964–93 (Gilgen et al, 1998)^[14]
• 2. 7%/decade (total 20 W/m²); up to 2000 (Stanhill and Cohen, 2001)^[15]
• 4% over 1961–90 (Liepert 2002)^[16][17]

Note that these numbers are for the terrestrial surface and not really a global average. Whether dimming (or brightening) occurred over the ocean has been a bit of an unknown though a specific measurement (see below, Causes) measured effects some 400 miles (643. 7 km) from India over the Indian Ocean towards the Maldives Islands. Regional effects probably dominate but are not strictly confined to the land area, and the effects will be driven by regional air circulation.

The largest reductions are found in the Northern Hemisphere mid-latitudes. Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball' ^[18] The region of the spectrum of light radiation most affected seems to be the visible and infrared rather than the ultraviolet part of the spectrum. A spectrum (plural spectra or spectrums) is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. For other uses see Visibility. Visible is billed as a not-for-profit free quarterly magazine dedicated to the history of Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays ^[19]

Pan evaporation data

Further information: Pan evaporation

Over the last 50 or so years, pan evaporation has been carefully monitored. Pan evaporation is a measurement that combines or integrates the effects of several climate elements temperature humidity solar radiation and wind Pan evaporation is a measurement that combines or integrates the effects of several climate elements temperature humidity solar radiation and wind For decades, nobody took much notice of the pan evaporation measurements. But in the 1990s in Europe, Israel, and North America, scientists spotted something that at the time was considered very strange, the rate of evaporation was falling although they had expected it to increase due to global warming. Global warming is the increase in the average measured temperature of the ^[20] The same trend has been observed in China over a similar period. A decrease in solar irradiance is cited to be the driving force. However, unlike in other areas of the world, in China the decrease in solar irradiance was not always accompanied by an increase in cloud cover and precipitation. It is believed that aerosols may play a critical role in the decrease of solar irradiance in China. Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas ^[21]

BBC Horizon producer David Sington believes that many climate scientists regard the pan-evaporation data as the most convincing evidence of solar dimming. Horizon is a current and long-running BBC popular Science and Philosophy documentary programme David Sington is a British -born producer screenwriter director author and journalist ^[22] Pan evaporation experiments are easy to reproduce with low-cost equipment, there are many pans used for agriculture all over the world and in many instances, and the data has been collected for nearly a half century. However, pan evaporation depends on some additional factors besides net radiation from the sun. The other two major factors are vapor pressure deficit and wind speed. ^[23] The ambient temperature turns out to be a negligible factor. The pan evaporation data corroborates the data gathered by radiometer^[15][20] and fills in the gaps in the data obtained using pyranometers. A radiometer is a device for measuring the radiant flux (power of Electromagnetic radiation. A pyranometer is a type of Actinometer used to measure broadband Solar irradiance on a planar surface and is a sensor that is designed to measure the solar radiation With adjustments to these factors, pan evaporation data has been compared to results of climate simulations. ^[24]

Probable causes

Further information: Particulate, Black carbon, Contrail, and Volcanic ash

NASA photograph showing aircraft contrails and natural clouds. Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas Black carbon or BC is formed through the incomplete combustion of fossil fuels biofuel and biomass and is emitted in both anthropogenic and naturally occurring soot Volcanic ash consists of small Tephra, which are bits of pulverized rock and glass created by volcanic eruptions less than in diameter The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The temporary disappearance of contrails over North America due to plane groundings after the September 11, 2001 attacks, and the resulting increase in diurnal temperature range gave empirical evidence of the effect of thin ice clouds at the Earth's surface. A day (symbol d is a unit of Time equivalent to 24 Hours and the duration of a single Rotation of planet Earth with respect to the Temperature range is the numerical difference between the minimum and maximum values of temperature observed in a system such as Atmospheric temperature in a given location Empirical research is any research that bases its findings on direct or indirect Observation as its test of Reality. ^[25]

The incomplete combustion of fossil fuels (such as diesel) and wood releases black carbon into the air. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum Black carbon or BC is formed through the incomplete combustion of fossil fuels biofuel and biomass and is emitted in both anthropogenic and naturally occurring soot Though black carbon, most of which is soot, is an extremely small component of air pollution at land surface levels, the phenomenon has a significant heating effect on the atmosphere at altitudes above two kilometers (6,562 feet). Soot (ˈsʊt is a general term that refers to the black impure carbon particles resulting from the incomplete combustion of a hydrocarbon Also, it dims the surface of the ocean by absorbing solar radiation. ^[26]

Experiments in the Maldives (comparing the atmosphere over the northern and southern islands) in the 1990s showed that the effect of macroscopic pollutants in the atmosphere at that time (blown south from India) caused about a 10% reduction in sunlight reaching the surface in the area under the pollution cloud — a much greater reduction than expected from the presence of the particles themselves. The Maldives ( or, or Maldive Islands) officially the Republic of Maldives, is an Island nation consisting of a group of atolls stretching India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country Pollution is the introduction of contaminants into an environment that causes instability disorder harm or discomfort to the physical systems or living organisms they are in ^[27] Prior to the research being undertaken, predictions were of a 0. 5–1% effect from particulate matter; the variation from prediction may be explained by cloud formation with the particles acting as the focus for droplet creation. Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas Clouds are very effective at reflecting light back out into space. Reflection is the change in direction of a Wave front at an interface between two different media so that the wave front returns into the medium from which

The phenomenon underlying global dimming may also have regional effects. While most of the earth has warmed, the regions that are downwind from major sources of air pollution (specifically sulfur dioxide emissions) have generally cooled. This may explain the cooling of the eastern United States relative to the warming western part. ^[28]

However some research shows that black carbon will actually increase global warming being second only to CO₂. They believe that soot will absorb solar energy and transport it to other areas such as the Himalayas where glacial melt occurs. It can also darken Arctic ice reducing reflectivity and increasing absorption of solar radiation. ^[29]

Some climate scientists have theorized that aircraft contrails (also called vapor trails) are implicated in global dimming, but the constant flow of air traffic previously meant that this could not be tested. The near-total shutdown of civil air traffic during the three days following the September 11, 2001 attacks afforded a rare opportunity in which to observe the climate of the United States absent from the effect of contrails. Civil aviation is one of two major categories of flying representing all non- Military aviation, both private and commercial The United States of America —commonly referred to as the During this period, an increase in diurnal temperature variation of over 1 °C (1. A day (symbol d is a unit of Time equivalent to 24 Hours and the duration of a single Rotation of planet Earth with respect to the The Celsius Temperature scale was previously known as the centigrade scale. 8 °F) was observed in some parts of the U. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 S. , i. e. aircraft contrails may have been raising nighttime temperatures and/or lowering daytime temperatures by much more than previously thought. ^[25]

Airborne volcanic ash can reflect the Sun's rays back out into space and cool the planet. Volcanic ash consists of small Tephra, which are bits of pulverized rock and glass created by volcanic eruptions less than in diameter Dips in earth temperatures have been observed from large volcano eruptions such as Mount Agung in Bali that erupted in 1963, El Chichon (Mexico) 1983, Ruiz (Colombia) 1985, and Pinatubo (Philippines) 1991. Mount Agung or Gunung Agung is a mountain in Bali. This Stratovolcano is the highest point on the island Nevado del Ruiz, also known as Mount Ruiz, is an Andean Stratovolcano in Caldas Department, Colombia. Mount Pinatubo is an active Stratovolcano located on the island of Luzon But even for major eruptions, the ash clouds remain only for relatively short periods. ^[30]

Recent reversal of the trend

Further information: Clean Air Act

Sun-blocking aerosols around the world steadily declined (red line) since the 1991 eruption of Mount Pinatubo, according to satellite estimates. A Clean Air Act describes one of a number of pieces of legislation relating to the reduction of Smog and Air pollution in general Credit: Michael Mishchenko, NASA

Wild et al, using measurements over land, report brightening since 1990,^[12][31][32] and Pinker et al^[33] found that slight dimming continued over land while brightening occurred over the ocean. ^[34] Hence, over the land surface, Wild et al and Pinker et al disagree. A 2007 NASA sponsored satellite-based study sheds light on the puzzling observations by other scientists that the amount of sunlight reaching Earth's surface had been steadily declining in recent decades, suddenly started to rebound around 1990. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program This switch from a "global dimming" trend to a "brightening" trend happened just as global aerosol levels started to decline. ^[30][35]

It is likely that at least some of this change, particularly over Europe, is due to decreases in pollution. Most governments of developed nations have done more to reduce aerosols released into the atmosphere, which helps reduce global dimming, than to reduce CO₂ emissions. The term developed country, or advanced country, is used to categorize countries with developed Economies in which the tertiary and quaternary sectors

Sulfate aerosols have declined significantly since 1970 with the Clean Air Act in the United States and similar policies in Europe. A Clean Air Act describes one of a number of pieces of legislation relating to the reduction of Smog and Air pollution in general The Clean Air Act was strengthened in 1977 and 1990. According to the EPA, from 1970 to 2005, total emissions of the six principal air pollutants, including PM’s, dropped by 53% in the US. In 1975, the masked effects of trapped greenhouse gases finally started to emerge and have dominated ever since. ^[36]

The Baseline Surface Radiation Network (BSRN) has been collecting surface measurements. Baseline Surface Radiation Network (BSRN is a project of the World Climate Research Programme (WCRP and the Global Energy and Water Cycle Experiment ( GEWEX) BSRN was started in the early 1990s and updated the archives in this time. Analysis of recent data reveals that the surface of the planet has brightened by about 4% in the past decade. The brightening trend is corroborated by other data, including satellite analyses.

Relationship to hydrological cycle

This figure shows the level of agreement between a climate model driven by five factors and the historical temperature record. This article is about the theories and mathematics of climate modeling See also Temperature record. The instrumental temperature record shows the fluctuations of the Temperature of the atmosphere and the oceans as The negative component identified as "sulfate" is associated with the aerosol emissions blamed for global dimming.

Further information: Hydrological cycle

Pollution produced by humans may be seriously weakening the Earth's water cycle — reducing rainfall and threatening fresh water supplies. The Earth 's Water is always in movement and the water cycle, also known as the hydrologic cycle, describes the continuous movement of water on above The Earth 's Water is always in movement and the water cycle, also known as the hydrologic cycle, describes the continuous movement of water on above A 2001 study by researchers at the Scripps Institution of Oceanography suggests that tiny particles of soot and other pollutants have a significant effect on the hydrological cycle. According to Professor V. Ramanathan: "The energy for the hydrological cycle comes from sunlight. As sunlight heats the ocean, water escapes into the atmosphere and falls out as rain. So as aerosols cut down sunlight by large amounts, they may be spinning down the hydrological cycle of the planet. "^[37]

Large scale changes in weather patterns may also have been caused by global dimming. Climate models speculatively suggest that this reduction in sunshine at the surface may have led to the failure of the monsoon in sub-Saharan Africa during the 1970s and 1980s, together with the associated famines such as the Sahel drought, caused by Northern hemisphere pollution cooling the Atlantic. This article is about the theories and mathematics of climate modeling A monsoon is a seasonal prevailing wind which lasts for several months The Sahara (الصحراء الكبرى aṣ-ṣaḥrā´ al-kubra, "The Great Desert" is the world's largest hot Desert and the world's second largest A famine is a widespread shortage of food that may apply to any Faunal species which phenomenon is usually accompanied by regional Malnutrition, Starvation The Sahel drought from the late 1960s to early 1980s created a Famine that killed a million people and afflicted more than 50 million ^[38] Because of this, the Tropical rain belt may not have risen to its northern latitudes, thus causing an absence of seasonal rains. The weather in the Tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year This claim is not universally accepted and is very difficult to test.

It is also concluded that the imbalance between global dimming and global warming at the surface leads to weaker turbulent heat fluxes to the atmosphere. This means globally reduced evaporation and hence precipitation occur in a dimmer and warmer world, which could ultimately lead to a more humid atmosphere in which it rains less. ^[39]

A natural form of large scale environmental shading/dimming has been identified that affected the 2006 northern hemisphere hurricane season. The NASA study found that several major dust storms in June and July in the Sahara desert sent dust drifting over the Atlantic Ocean and through several effects caused cooling of the waters — and thus dampening the development of hurricanes. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The Sahara (الصحراء الكبرى aṣ-ṣaḥrā´ al-kubra, "The Great Desert" is the world's largest hot Desert and the world's second largest ^[40][41]

Relationship to global warming

Further information: Global warming

Some scientists now consider that the effects of global dimming have masked the effect of global warming to some extent and that resolving global dimming may therefore lead to increases in predictions of future temperature rise. Global warming is the increase in the average measured temperature of the Global warming is the increase in the average measured temperature of the ^[17] According to Beate Liepert, "We lived in a global warming plus a global dimming world and now we are taking out global dimming. So we end up with the global warming world, which will be much worse than we thought it will be, much hotter. "^[42] The magnitude of this masking effect is one of the central problems in climate change with significant implications for future climate changes and policy responses to global warming. ^[43]

But it's much more complicated than an either warming or dimming issue. Global warming and global dimming are not mutually exclusive or contradictory. In a paper published on March 8, 2005 in the American Geophysical Union's Geophysical Research Letters, a research team led by Anastasia Romanou of Columbia University's Department of Applied Physics and Mathematics, New York, also showed that the apparently opposing forces of global warming and global dimming can occur at the same time. Events 1618 - Johannes Kepler discovers the third law of planetary motion. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. ^[44] Global dimming interacts with global warming by blocking sunlight that would otherwise cause evaporation and the particulates bind to water droplets. Water vapor is one of the greenhouse gases. On the other hand, global dimming is affected by evaporation and rain. Rain has the effect of clearing out polluted skies.

Brown clouds have been found to amplify global warming according to V. Ramanathan, an atmospheric chemist at the Scripps Institution of Oceanography in La Jolla, CA. "The conventional thinking is that brown clouds have masked as much as 50 percent of global warming by greenhouse gases through so-called global dimming," . . . "While this is true globally, this study reveals that over southern and eastern Asia, the soot particles in the brown clouds are in fact amplifying the atmospheric warming trend caused by greenhouse gases by as much as 50 percent. "^[45]

Possible use to mitigate global warming

Further information: Mitigation of global warming and Albedo

Some scientists have suggested using aerosols to stave off the effects of global warming as an emergency measure. Mitigation of global warming involves taking actions to reduce Greenhouse gas emissions and to enhance sinks aimed at reducing the extent of Global warming The albedo of an object is the extent to which it diffusely reflects light from the sun Russian expert Mikhail Budyko understood this relationship very early on. Mikhail Ivanovich Budyko (Михаил Иванович Будыко (born January 20 1920 Gomel, Belarus) is a Russian Climatologist and one In 1974, he suggested that if global warming became a problem, the planet could be cooled by burning sulfur in the stratosphere, which would create a haze. ^[46][47][48] According to Ramanathan (1988), an increase in planetary albedo of just 0. The albedo of an object is the extent to which it diffusely reflects light from the sun 5 percent is sufficient to halve the effect of a CO₂ doubling. ^[49]

However, Earth would still face many problems, such as:

• Using sulfates causes environmental problems such as acid rain^[50]
• Using carbon black causes human health problems^[50]
• Dimming causes ecological problems such as changes in evaporation and rainfall patterns^[50]
• Droughts and/or increased rainfall cause problems for agriculture^[50]
• Aerosol has a relatively short lifetime

"Ideas that we should increase aerosol emissions to counteract global warming have been described as a 'Faustian bargain' because that would imply an ever increasing amount of emissions in order to match the accumulated greenhouse gas in the atmosphere, with ever increasing monetary and health costs. A deal with the Devil, pact with the Devil, or Faustian bargain is a cultural motif widespread wherever the Devil is vividly present most familiar "^[51] Climatologists are stressing that the roots of both global dimming-causing pollutants and global warming-causing greenhouse gases have to be dealt with together and soon. ^[52]

See also

• Climate change
• Insolation
• Iris hypothesis
• Global cooling
• Snowball Earth
• Solar variation
• Sunshine recorders
• Ship tracks

References

External links

Bibliographies

• Roderick, Michael. Global Dimming Bibliography (English).
• Saunders, Alison. Global Dimming Bibliography (English).

Notable web pages

• Global Dimming summary (English). BBC Horizon.
• Liepert, Beate. Global Dimming (requires flash) (English).
• Global Dimming - part 1 (English). Realclimate. org.
• Global Dimming - part 2 (English). Realclimate. org.
• Global Dimming may have a brighter future (English). Realclimate. org.
• Veiling Our True Predicament: Global Dimming - Easy to Understand Primer on Global Dimming, also including BBC documentary on the subject.

Podcasts

• Brown Cloud (mp3) (English). Ecoshock.

Q&A

• BBC Global Dimming Q&A (English).

News articles

• Adam, David. "Goodbye Sunshine", The Guardian, 2003-12-18. The Guardian (until 1959 The Manchester Guardian) is a British Newspaper owned by the Guardian Media Group. Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. Events 218 BC - Second Punic War: Battle of the Trebia - Hannibal 's Carthaginian forces defeat those of the (English) 
• Chang, Kenneth. "Globe Grows Darker as Sunshine Diminishes 10% to 37%", The New York Times, 2004-05-13. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Events 1497 - Pope Alexander VI excommunicates Girolamo Savonarola. (English) 
• Appell, David. "The Darkening Earth Less sun at the Earth's surface complicates climate models", Scientific American, 2004-08-02. Scientific American is a Popular science magazine, published (first weekly and later monthly since August 28, 1845, making it "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Events 338 BC - A Macedonian army led by Philip II defeated the combined forces of Athens and Thebes in the (English) 
• Keen, Kip. "Dim Sun Global dimming? Global warming? What's with the globe, anyway?", Grist Magazine, 2004-09-22. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Events 66 - Emperor Nero creates the Legion I Italica. 1236 - The Lithuanians (English) 
• Sington, David. "Why the Sun seems to be 'dimming'", BBC News, 2005-01-13. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Events 532 - Nika riots in Constantinople. 888 - Odo Count of Paris becomes King of the Franks (English) 
• Onion, Amanda. "Are Skies Dimming Over Earth? Data Suggest Human Pollution Can Lead to Darker Days", ABC News, 2006-02-09. This article is about the American news organization See also ABC News (disambiguation ABC News is a division of American Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 474 - Zeno crowned as co-emperor of the Byzantine Empire. (English) 
• "Transported Black Carbon A Significant Player In Pacific Ocean Climate", Science Daily, 2007-03-15. Dan Hogan Editoreditor@sciencedailycom Michele Hogan Sales Managersales@sciencedaily Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 44 BC - Julius Caesar, Dictator of the Roman Republic, is stabbed to death by Marcus Junius Brutus, (English) 
• "Global 'Sunscreen' Has Likely Thinned, Report NASA Scientists", NASA, 2007-03-15. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 44 BC - Julius Caesar, Dictator of the Roman Republic, is stabbed to death by Marcus Junius Brutus, (English) 
• Seinfeld, John (January 2008). "Atmospheric science: Black carbon and brown clouds". Nature Geoscience 1 (1): 15–6. Nature Geoscience is a Scientific journal published by Nature Publishing Group, publisher of the flagship journal Nature. doi:10.1038/ngeo.2007.62. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  

Slide decks

• Atmospheric Aerosol and Air Pollution.

Television programs

• Report on another consequence of global warming: the dimming effect of clouds (English). BBC2 TV Horizon (2005-01-15). Horizon is a current and long-running BBC popular Science and Philosophy documentary programme Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Events 588 BC - Nebuchadrezzar II of Babylon lays siege to Jerusalem under Zedekiah 's reign
• Dimming The Sun (English). PBS WGBH Boston NOVA (2006-04-18). Nova is a Popular science Television series from the US produced by WGBH Boston Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1025 - Bolesław Chrobry is crowned in Gniezno, becoming the first King of Poland.
• BBC Horizon - Global Dimming - Google Video (english). BBC Horizon.