Perhaps the overriding theme of these definitions is the ability of the environment to absorb and adapt to changes brought about by human activities.
In one word, environmental pollution takes place when the environment cannot process and neutralize harmful by-products of human activities (for example, poisonous gas emissions) in due course without any structural or functional damage to its system.
In fact, “the due course” itself may last many years during which the nature will attempt to decompose the pollutants; in one of the worst cases – that of radioactive pollutants – it may take as long as thousands of years for the decomposition of such pollutants to be completed.
Pollution occurs, on the one hand, because the natural environment does not know how to decompose the unnaturally generated elements (i.e., anthropogenic pollutants), and, on the other, there is a lack of knowledge on the part of humans on how to decompose these pollutants artificially.
Why does pollution matter
It matters first and foremost because it has negative impacts on crucial environmental services such as provision of clean air and clean water (and many others) without which life on Earth as we know it would not exist.
Introduction to Environmental Pollution
Although pollution had been known to exist for a very long time (at least since people started using fire thousands of years ago), it had seen the growth of truly global proportions only since the onset of the industrial revolution during the 19th century.
The industrial revolution brought with it technological progress such as discovery of oil and its virtually universal use throughout different industries.
Technological progress facilitated by super efficiency of capitalist business practices (division of labour – cheaper production costs – overproduction – overconsumption – overpollution) had probably become one of the main causes of serious deterioration of natural resources.
At the same time, of course, development of natural sciences led to the better understanding of negative effects produced by pollution on the environment.
Environmental pollution is a problem both in developed and developing countries. Factors such as population growth and urbanization invariably place greater demands on the planet and stretch the use of natural resources to the maximum.
It has been argued that the carrying capacity of Earth is significantly smaller than the demands placed on it by large numbers of human populations. And overuse of natural resources often results in nature’s degradation.
It’s interesting to note that natural resources had been stored virtually untouched in the Earth for millions of years.
But since the start of the industrial revolution vast amounts of these resources had been exploited within a period of just a couple of hundred of years at unimaginable rates, with all the waste from this exploitation going straight in to the environment (air, water, land) and seriously damaging its natural processes.
Types of Environmental Pollution
There are three major types of environmental pollution
Soil pollution (contamination)
For a list of other pollution types, please see the Types of Pollution article.
Some of the most important air pollutants are sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, volatile organic compounds (VOCs) and airborne particles, with radioactive pollutants probably among the most destructive ones (specifically when produced by nuclear explosions).
Please refer to the Summary of Air Pollutants article for a brief overview of sources and effects of air pollutants.
Water pollutants include insecticides and herbicides, food processing waste, pollutants from livestock operations, volatile organic compounds (VOCs), heavy metals, chemical waste and others.
Some soil pollutants are hydrocarbons, solvents and heavy metals.
Sources of Environmental Pollution
Fossil Fuel Sources of Environmental Pollution
Fossil Fuel Pollution
Photo Rachel Scopes
In modern industrialized societies, fossil fuels (oil, gas, coal) transcended virtually all imaginable barriers and firmly established themselves in our everyday lives.
Not only do we use fossil fuels for our obvious everyday needs (such as filling a car), as well as in the power-generating industry, they (specifically oil) are also present in such products as all sorts of plastics, solvents, detergents, asphalt, lubricating oils, a wide range of chemicals for industrial use, etc. (8)
Combustion of fossil fuels produces extremely high levels of air pollution and is widely recognized as one of the most important “target” areas for reduction and control of environmental pollution.
Fossil fuels also contribute to soil contamination and water pollution. For example, when oil is transported from the point of its production to further destinations by pipelines, an oil leak from the pipeline may occur and pollute soil and subsequently groundwater. When oil is transported by tankers by ocean, an oil spill may occur and pollute ocean water.
Of course, there are other natural resources whose exploitation is a cause of serious pollution; for example, the use of uranium for nuclear power generation produces extremely dangerous waste that would take thousands of years to neutralize.
But there is no reasonable doubt that fossil fuels are among the most serious sources of environmental pollution.
Power-generating plants and transport are probably the biggest sources of fossil fuel pollution.
Common sources of fossil fuel pollution are (9)
Production and distribution of fossil fuels
Other manufacturing facilities
Road transport (motor vehicles)
Fossil fuel combustion is also a major source of carbon dioxide (CO2) emissions and perhaps the most important cause of global warming. Learn more about the causes and effects of global warming here.
Other (Non-Fossil Fuel) Sources of Environmental Pollution
Among other pollution sources, agriculture (livestock farming) is worth mentioning as the largest generator of ammonia emissions resulting in air pollution. Chemicals such as pesticides and fertilizers are also widely used in agriculture, which may lead water pollution and soil contamination as well.
Trading activities may be another source of pollution.
For example, it’s been recently noted that packaging of products sold in supermarkets and other retail outlets is far too excessive and generates large quantities of solid waste that ends up either in landfills or municipal incinerators leading to soil contamination and air pollution.
Residential sector is another significant source of pollution generating solid municipal waste that may end up in landfills or incinerators leading to soil contamination and air pollution.
We discuss air pollution causes in more detail here.
How can we control environmental pollution
It’s clear that fossil fuels are among the biggest sources of pollution. We need to find alternative renewable sources of energy which can replace fossil fuels in the future.
Green investment provides a great platform to explore and develop new and clean sources of energy such as solar electricity.
Building your own solar panels and using diy solar energy systems to meet at least part of your home electricity needs is another emerging opportunity for diy enthusiasts. This can really make a positive difference to the environment and reduce current pollution levels.
Environmental Pollution Effects on Humans, Other Animals & Plants
General Environmental Pollution Effects
Miguel A. Santos notes that a very important aspect of the effect of pollution is its dose (or concentration) required to cause environmental damage. (10)
He defines pollution response as “the change in the effect of a pollutant in response to a change in its concentration”. (11)
In this respect, he identifies 3 different types of response evoked by the environment to different pollution concentrations (12)
In the linear effect, environmental damage increases linearly with pollution concentrations. In other words, “ the total damage or risk is directly proportional to the accumulated exposure”. (13)
This effect occurs with radioactive substances as well as mercury, lead, cadmium and asbestos.
In the greater-than-linear effect, environmental damage increases with an increase in pollution concentrations but at a decreasing rate. This means that, as pollution concentrations continue to increase the environmental damage will continue to decrease. (14)
This is the case with thermal pollution.
In the threshold effect, pollution produces no effect until a certain threshold in pollution concentrations is achieved. In other words, “so long as a given threshold is not exceeded, the damage from pollution would be completely repaired as quickly as it is produced”. (15)
This effect is found with biodegradable pollutants.
It is also important to mention synergistic effects of pollutants on the environment. While interacting with each other, pollutants can produce greater impacts than when acting individually. (16)
A good example of that is a synergy between asbestos exposure and smoking in causing lung cancer. (17)
There is no doubt that excessive levels of pollution are causing a lot of damage to human & animal health, plants & trees (including tropical rainforests) as well as the wider environment.
All types of environmental pollution – air, water and soil pollution – have an impact on the living environment.
The effects in living organisms may range from mild discomfort to serious diseases such as cancer to physical deformities (for example, extra or missing limbs in frogs).
Experts admit that environmental pollution effects are quite often underestimated and that more research is needed to understand the connections between pollution and its effects on all life forms.
Environmental Pollution Effects on Humans
We know that pollution causes not only physical disabilities but also psychological and behavioral disorders in people.
We are discussing the effects of air pollution and specific air pollutants in more detail in the Air Pollutants article.
The following effects of environmental pollution on humans have been reported
Air Pollution in Philippines
Photo Jim D Stitch
Air pollution (18, 19)
Reduced lung functioning
Irritation of eyes, nose, mouth and throat
Respiratory symptoms such as coughing and wheezing
Increased respiratory disease such as bronchitis
Reduced energy levels
Headaches and dizziness
Disruption of endocrine, reproductive and immune systems
We discuss air pollution effects in more detail here.
Water pollution (20)
Waterborne diseases caused by polluted drinking water
Waterborne diseases caused by polluted beach water
Rashes, ear ache, pink eye
Hepatitis, encephalitis, gastroenteritis, diarrhoea, vomiting, and stomach aches
Conditions related to water polluted by chemicals (such as pesticides, hydrocarbons, persistent organic pollutants, heavy metals etc)
Cancer, incl. prostate cancer and non-Hodgkin’s lymphoma
Hormonal problems that can disrupt reproductive and developmental processes
Damage to the nervous system
Liver and kidney damage
Damage to the DNA
Exposure to mercury (heavy metal)
In the womb may cause neurological problems including slower reflexes, learning deficits, delayed or incomplete mental development, autism and brain damage
In adults Parkinson’s disease, multiple sclerosis, Alzheimer’s disease, heart disease, and even death
Water pollution may also result from interactions between water and contaminated soil, as well as from deposition of air contaminants (such as acid rain)
Damage to people may be caused by fish foods coming from polluted water (a well known example is high mercury levels in fish)
Damage to people may be caused by vegetable crops grown washed with polluted water (author’s own conclusion)
Soil contamination (21)
Causes cancers including leukaemia
Lead in soil is especially hazardous for young children causing developmental damage to the brain
Mercury can increase the risk of kidney damage; cyclodienes can lead to liver toxicity
Causes neuromuscular blockage as well as depression of the central nervous system
Also causes headaches, nausea, fatigue, eye irritation and skin rash
Contact with contaminated soil may be direct (from using parks, schools etc) or indirect (by inhaling soil contaminants which have vaporized)
Soil contamination may also result from secondary contamination of water supplies and from deposition of air contaminants (for example, via acid rain)
Contamination of crops grown in polluted soil brings up problems with food security
Since it is closely linked to water pollution, many effects of soil contamination appear to be similar to the ones caused by water contamination
An Extreme Oil Pollution Case
Pollution of pristine Ecuador rainforest by Texaco Chevron oil corporation represents perhaps one of the most outrageous cases of oil pollution ever.
Some levels of pollutants left by the company on its sites of oil exploration have been calculated to exceed the US safety standards by as much as 1,000 times, causing such side effects as children born with fused fingers and deformed eyes, high cancer rates, etc.
For more details, check out the Oil Pollution of Ecuador Rainforest article.
Environmental Pollution Effects on Animals
Air Pollution (22)
Acid rain (formed in the air) destroys fish life in lakes and streams
Excessive ultraviolet radiation coming from the sun through the ozone layer in the upper atmosphere which is eroded by some air pollutants, may cause skin cancer in wildlife
Ozone in the lower atmosphere may damage lung tissues of animals
Water Pollution (23)
Nutrient pollution (nitrogen, phosphates etc) causes overgrowth of toxic algae eaten by other aquatic animals, and may cause death; nutrient pollution can also cause outbreaks of fish diseases
Chemical contamination can cause declines in frog biodiversity and tadpole mass
Oil pollution (as part of chemical contamination) can negatively affect development of marine organisms, increase susceptibility to disease and affect reproductive processes; can also cause gastrointestinal irritation, liver and kidney damage, and damage to the nervous system
Mercury in water can cause abnormal behavior, slower growth and development, reduced reproduction, and death
Persistent organic pollutants (POPs) may cause declines, deformities and death of fish life
Too much sodium chloride (ordinary salt) in water may kill animals (24)
We also assume that some higher forms of non-aquatic animals may have similar effects from water pollution as those experienced by humans, as described above (author’s own conclusion)
Soil Contamination (25)
Can alter metabolism of microorganisms and arthropods in a given soil environment; this may destroy some layers of the primary food chain, and thus have a negative effect on predator animal species
Small life forms may consume harmful chemicals which may then be passed up the food chain to larger animals; this may lead to increased mortality rates and even animal extinction
Environmental Pollution Effects on Trees and Plants
Air Pollution (26)
Acid rain can kill trees, destroy the leaves of plants, can infiltrate soil by making it unsuitable for purposes of nutrition and habitation
Ozone holes in the upper atmosphere can allow excessive ultraviolet radiation from the sun to enter the Earth causing damage to trees and plants
Ozone in the lower atmosphere can prevent plant respiration by blocking stomata (openings in leaves) and negatively affecting plants’ photosynthesis rates which will stunt plant growth; ozone can also decay plant cells directly by entering stomata
May disrupt photosynthesis in aquatic plants and thus affecting ecosystems that depend on these plants (27)
Terrestrial and aquatic plants may absorb pollutants from water (as their main nutrient source) and pass them up the food chain to consumer animals and humans
Plants may be killed by too much sodium chloride (ordinary slat) in water (28)
Plants may be killed by mud from construction sites as well as bits of wood and leaves, clay and other similar materials (29)
Plants may be killed by herbicides in water; herbicides are chemicals which are most harmful to plants (30)
May alter plant metabolism and reduce crop yields (31)
Trees and plants may absorb soil contaminants and pass them up the food chain
Environmental Pollution Effects on Wider Environment
Apart from destroying the aquatic life in lakes and streams, acid rain can also corrode metals, damage surfaces of buildings and monuments, and cause soil acidification.
Pollution of water may cause oxygen depletion in marine environments and severely affect the health of whole ecosystems. (32)
Environmental Pollution – Conclusion
Environmental pollution is causing a lot of distress not only to humans but also animals, driving many animal species to endangerment and even extinction.
Pollution is Not Glamorous
Photo Caleb Coppola
The transboundary nature of environmental pollution makes it even more difficult to manage – you cannot build stone walls along the borders of your country or put customs cabins at every point of entry to regulate its flows into your country.
Everything on our planet is interconnected, and while the nature supplies us with valuable environmental services without which we cannot exist, we all depend on each other’s actions and the way we treat natural resources.
It’s widely recognised that we are hugely overspending our current budget of natural resources – at the existing rates of its exploitation, there is no way for the environment to recover in good time and continue “performing” well in the future.
Perhaps we should adopt a holistic view of nature – it is not an entity that exists separately from us; the nature is us, we are an inalienable part of it, and we should care for it in the most appropriate manner. Only then can we possibly solve the problem of environmental pollution.
What is the way forward
The nature is not going to survive the demands that we currently place on it, for much longer.
We certainly need to get our act together and stop using dirty technologies.
Line plot of global mean land-ocean temperature change from 1880-2010, relative to the 1951-1980 mean. The black line is the annual mean and the red line is the 5-year running mean. The green bars show uncertainty estimates. Source: NASA GISS
Comparison of surface based (blue) and satellite based (red: UAH; green: RSS) records of global mean temperature change from 1979-2009. Linear trends plotted since 1982.
The map shows the 10-year average (2000-2009) global mean temperature anomaly relative to the 1951-1980 mean. The largest temperature increases are in the Arctic and the Antarctic Peninsula. Source: NASA Earth Observatory 
Global warming is the increase in the average temperature of Earth’s near-surface air and oceans since the mid-20th century and its projected continuation. According to the 2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC), global surface temperature increased by 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 20th century.[A] Most of the observed temperature increase since the middle of the 20th century has been caused by increasing concentrations of greenhouse gases, which result from human activities such as the burning of fossil fuel and deforestation. Global dimming, a phenomenon of increasing atmospheric concentrations of human-made particulates, which affect cloud properties and block sunlight from reaching the surface, has partially countered the effects of warming induced by greenhouse gases.
Climate model projections summarized in the 2007 IPCC report indicate that the global surface temperature is likely to rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century. The uncertainty in this estimate arises from the use of models with differing sensitivity to greenhouse gas concentrations and the use of differing estimates of future greenhouse gas emissions. An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, probably including expansion of subtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects of the warming include more frequent and intense precipitation events, extreme weather events, species extinctions due to shifting isotherms, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional changes is uncertain. As a result of contemporary increases in atmospheric carbon dioxide, the oceans have become more acidic, a result that is predicted to continue.
The scientific consensus is that anthropogenic global warming is occurring. This finding is recognized by the national science academies of all the major industrialized countries and is not rejected by any scientific body of national or international standing.[B] Nevertheless, skepticism amongst the wider public remains. The Kyoto Protocol is aimed at stabilizing greenhouse gas concentration to prevent a "dangerous anthropogenic interference". As of November 2009, 187 states had signed and ratified the protocol. Proposed responses to global warming include mitigation to reduce emissions, adaptation to the effects of global warming, and geoengineering to remove greenhouse gases from the atmosphere.Contents
1 Temperature changes
2 External forcings
2.1 Greenhouse gases
2.2 Particulates and soot
2.3 Solar variation
4 Climate models
5 Attributed and expected effects
5.1 Natural systems
5.2 Ecological systems
5.3 Social systems
6 Responses to global warming
7 Views on global warming
7.2 Public opinion
7.3 Other views
9 See also
12 Further reading
13 External links
Main article: Temperature record
Two millennia of mean surface temperatures according to different reconstructions, each smoothed on a decadal scale, with the instrumemtal temperature record overlaid in black.
Evidence for warming of the climate system includes observed increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level. The most common measure of global warming is the trend in globally averaged temperature near the Earth’s surface. Expressed as a linear trend, this temperature rose by 0.74 ± 0.18 °C over the period 1906–2005. The rate of warming over the last half of that period was almost double that for the period as a whole (0.13 ± 0.03 °C per decade, versus 0.07 °C ± 0.02 °C per decade). The urban heat island effect is estimated to account for about 0.002 °C of warming per decade since 1900. Temperatures in the lower troposphere have increased between 0.13 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with regionally varying fluctuations such as the Medieval Warm Period and the Little Ice Age.
Estimates by NASA’s Goddard Institute for Space Studies (GISS) and the National Climatic Data Center show that 2005 was the planet’s warmest year since reliable, widespread instrumental measurements became available in the late 19th century, exceeding the previous record set in 1998 by a few hundredths of a degree. Estimates prepared by the World Meteorological Organization and the Climatic Research Unit show 2005 as the second warmest year, behind 1998. Temperatures in 1998 were unusually warm because the strongest El Ni?o in the past century occurred during that year. Global temperature is subject to short-term fluctuations that overlay long term trends and can temporarily mask them. The relative stability in temperature from 2002 to 2009 is consistent with such an episode.
Temperature changes vary over the globe. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C per decade against 0.13 °C per decade). Ocean temperatures increase more slowly than land temperatures because of the larger effective heat capacity of the oceans and because the ocean loses more heat by evaporation. The Northern Hemisphere warms faster than the Southern Hemisphere because it has more land and because it has extensive areas of seasonal snow and sea-ice cover subject to ice-albedo feedback. Although more greenhouse gases are emitted in the Northern than Southern Hemisphere this does not contribute to the difference in warming because the major greenhouse gases persist long enough to mix between hemispheres.
The thermal inertia of the oceans and slow responses of other indirect effects mean that climate can take centuries or longer to adjust to changes in forcing. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0.5 °C (0.9 °F) would still occur.
External forcing refers to processes external to the climate system (though not necessarily external to Earth) that influence climate. Climate responds to several types of external forcing, such as radiative forcing due to changes in atmospheric composition (mainly greenhouse gas concentrations), changes in solar luminosity, volcanic eruptions, and variations in Earth’s orbit around the Sun. Attribution of recent climate change focuses on the first three types of forcing. Orbital cycles vary slowly over tens of thousands of years and thus are too gradual to have caused the temperature changes observed in the past century.
Main articles: Greenhouse effect, Radiative forcing, and Carbon dioxide in Earth’s atmosphere
Greenhouse effect schematic showing energy flows between space, the atmosphere, and earth’s surface. Energy exchanges are expressed in watts per square meter (W/m2).
This graph is known as the "Keeling Curve" and it shows the long-term increase of atmospheric carbon dioxide (CO2) concentrations from 1958-2008. Monthly CO2 measurements display seasonal oscillations in an upward trend; each year’s maximum occurs during the Northern Hemisphere’s late spring, and declines during its growing season as plants remove some atmospheric CO2.
The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet’s lower atmosphere and surface. It was proposed by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896.
Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F).[C] The major greenhouse gases are water vapor, which causes about 36–70 percent of the greenhouse effect; carbon dioxide (CO2), which causes 9–26 percent; methane (CH4), which causes 4–9 percent; and ozone (O3), which causes 3–7 percent. Clouds also affect the radiation balance, but they are composed of liquid water or ice and so have different effects on radiation from water vapor.
Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from CO2, methane, tropospheric ozone, CFCs and nitrous oxide. The concentrations of CO2 and methane have increased by 36% and 148% respectively since 1750. These levels are much higher than at any time during the last 800,000 years, the period for which reliable data has been extracted from ice cores. Less direct geological evidence indicates that CO2 values higher than this were last seen about 20 million years ago. Fossil fuel burning has produced about three-quarters of the increase in CO2 from human activity over the past 20 years. The rest of this increase is caused mostly by changes in land-use, particularly deforestation.
Over the last three decades of the 20th century, GDP per capita and population growth were the main drivers of increases in greenhouse gas emissions. CO2 emissions are continuing to rise due to the burning of fossil fuels and land-use change.:71 Emissions scenarios, estimates of changes in future emission levels of greenhouse gases, have been projected that depend upon uncertain economic, sociological, technological, and natural developments. In most scenarios, emissions continue to rise over the century, while in a few, emissions are reduced. These emission scenarios, combined with carbon cycle modelling, have been used to produce estimates of how atmospheric concentrations of greenhouse gases will change in the future. Using the six IPCC SRES "marker" scenarios, models suggest that by the year 2100, the atmospheric concentration of CO2 could range between 541 and 970 ppm. This is an increase of 90-250% above the concentration in the year 1750. Fossil fuel reserves are sufficient to reach these levels and continue emissions past 2100 if coal, oil sands or methane clathrates are extensively exploited.
The popular media and the public often confuse global warming with the ozone hole, i.e., the destruction of stratospheric ozone by chlorofluorocarbons. Although there are a few areas of linkage, the relationship between the two is not strong. Reduced stratospheric ozone has had a slight cooling influence on surface temperatures, while increased tropospheric ozone has had a somewhat larger warming effect.
Particulates and soot
Ship tracks over the Atlantic Ocean on the east coast of the United States. The climatic impacts from particulate forcing could have a large effect on climate through the indirect effect.
Global dimming, a gradual reduction in the amount of global direct irradiance at the Earth’s surface, has partially counteracted global warming from 1960 to the present. The main cause of this dimming is particulates produced by volcanoes and pollutants, which exerts a cooling effect by increasing the reflection of incoming sunlight. The effects of the products of fossil fuel combustion—CO2 and aerosols—have largely offset one another in recent decades, so that net warming has been due to the increase in non-CO2 greenhouse gases such as methane. Radiative forcing due to particulates is temporally limited due to wet deposition which causes them to have an atmospheric lifetime of one week. Carbon dioxide has a lifetime of a century or more, and as such, changes in particulate concentrations will only delay climate changes due to carbon dioxide.
In addition to their direct effect by scattering and absorbing solar radiation, particulates have indirect effects on the radiation budget. Sulfates act as cloud condensation nuclei and thus lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets, known as the Twomey effect. This effect also causes droplets to be of more uniform size, which reduces growth of raindrops and makes the cloud more reflective to incoming sunlight, known as the Albrecht effect. Indirect effects are most noticeable in marine stratiform clouds, and have very little radiative effect on convective clouds. Indirect effects of particulates represent the largest uncertainty in radiative forcing.
Soot may cool or warm the surface, depending on whether it is airborne or deposited. Atmospheric soot directly absorb solar radiation, which heats the atmosphere and cools the surface. In isolated areas with high soot production, such as rural India, as much as 50% of surface warming due to greenhouse gases may be masked by atmospheric brown clouds. When deposited, especially on glaciers or on ice in arctic regions, the lower surface albedo can also directly heat the surface. The influences of particulates, including black carbon, are most pronounced in the tropics and sub-tropics, particularly in Asia, while the effects of greenhouse gases are dominant in the extratropics and southern hemisphere.
Main article: Solar variation
Total Solar Irradiance measured by satellite from 1979-2006.
Variations in solar output have been the cause of past climate changes. The effect of changes in solar forcing in recent decades is uncertain, but small, with some studies showing a slight cooling effect, while others studies suggest a slight warming effect.
Greenhouse gases and solar forcing affect temperatures in different ways. While both increased solar activity and increased greenhouse gases are expected to warm the troposphere, an increase in solar activity should warm the stratosphere while an increase in greenhouse gases should cool the stratosphere. Observations show that temperatures in the stratosphere have been cooling since 1979, when satellite measurements became available. Radiosonde (weather balloon) data from the pre-satellite era show cooling since 1958, though there is greater uncertainty in the early radiosonde record.
A related hypothesis, proposed by Henrik Svensmark, is that magnetic activity of the sun deflects cosmic rays that may influence the generation of cloud condensation nuclei and thereby affect the climate. Other research has found no relation between warming in recent decades and cosmic rays. The influence of cosmic rays on cloud cover is about a factor of 100 lower than needed to explain the observed changes in clouds or to be a significant contributor to present-day climate change.
Main article: Climate change feedback
Feedback is a process in which changing one quantity changes a second quantity, and the change in the second quantity in turn changes the first. Positive feedback increases the change in the first quantity while negative feedback reduces it. Feedback is important in the study of global warming because it may amplify or diminish the effect of a particular process. The main positive feedback in global warming is the tendency of warming to increase the amount of water vapor in the atmosphere, a significant greenhouse gas. The main negative feedback is radiative cooling, which increases as the fourth power of temperature; the amount of heat radiated from the Earth into space increases with the temperature of Earth’s surface and atmosphere. Imperfect understanding of feedbacks is a major cause of uncertainty and concern about global warming. A wide range of potential feedback process exist, such as Arctic methane release and ice-albedo feedback. Consequentially, potential tipping points may exist, which may have the potential to cause abrupt climate change.
Main article: Global climate model
Calculations of global warming prepared in or before 2001 from a range of climate models under the SRES A2 emissions scenario, which assumes no action is taken to reduce emissions and regionally divided economic development.
The geographic distribution of surface warming during the 21st century calculated by the HadCM3 climate model if a business as usual scenario is assumed for economic growth and greenhouse gas emissions. In this figure, the globally averaged warming corresponds to 3.0 °C (5.4 °F).
The main tools for projecting future climate changes are mathematical models based on physical principles including fluid dynamics, thermodynamics and radiative transfer. Although they attempt to include as many processes as possible, simplifications of the actual climate system are inevitable because of the constraints of available computer power and limitations in knowledge of the climate system. All modern climate models are in fact combinations of models for different parts of the Earth. These include an atmospheric model for air movement, temperature, clouds, and other atmospheric properties; an ocean model that predicts temperature, salt content, and circulation of ocean waters; models for ice cover on land and sea; and a model of heat and moisture transfer from soil and vegetation to the atmosphere. Some models also include treatments of chemical and biological processes. Warming due to increasing levels of greenhouse gases is not an assumption of the models; rather, it is an end result from the interaction of greenhouse gases with radiative transfer and other physical processes. Although much of the variation in model outcomes depends on the greenhouse gas emissions used as inputs, the temperature effect of a specific greenhouse gas concentration (climate sensitivity) varies depending on the model used. The representation of clouds is one of the main sources of uncertainty in present-generation models.
Global climate model projections of future climate most often have used estimates of greenhouse gas emissions from the IPCC Special Report on Emissions Scenarios (SRES). In addition to human-caused emissions, some models also include a simulation of the carbon cycle; this generally shows a positive feedback, though this response is uncertain. Some observational studies also show a positive feedback. Including uncertainties in future greenhouse gas concentrations and climate sensitivity, the IPCC anticipates a warming of 1.1 °C to 6.4 °C (2.0 °F to 11.5 °F) by the end of the 21st century, relative to 1980–1999.
Models are also used to help investigate the causes of recent climate change by comparing the observed changes to those that the models project from various natural and human-derived causes. Although these models do not unambiguously attribute the warming that occurred from approximately 1910 to 1945 to either natural variation or human effects, they do indicate that the warming since 1970 is dominated by man-made greenhouse gas emissions.
The physical realism of models is tested by examining their ability to simulate current or past climates. Current climate models produce a good match to observations of global temperature changes over the last century, but do not simulate all aspects of climate. Not all effects of global warming are accurately predicted by the climate models used by the IPCC. Observed Arctic shrinkage has been faster than that predicted. Precipitation increased proportional to atmospheric humidity, and hence significantly faster than current global climate models predict.
Attributed and expected effects
Main articles: Effects of global warming and Regional effects of global warming
Global warming may be detected in natural, ecological or social systems as a change having statistical significance. Attribution of these changes e.g., to natural or human activities, is the next step following detection.
Sparse records indicate that glaciers have been retreating since the early 1800s. In the 1950s measurements began that allow the monitoring of glacial mass balance, reported to the WGMS and the NSIDC.
Global warming has been detected in a number of systems. Some of these changes, e.g., based on the instrumental temperature record, have been described in the section on temperature changes. Rising sea levels and observed decreases in snow and ice extent are consistent with warming. Most of the increase in global average temperature since the mid-20th century is, with high probability,[D] attributable to human-induced changes in greenhouse gas concentrations.
Even with current policies to reduce emissions, global emissions are still expected to continue to grow over the coming decades. Over the course of the 21st century, increases in emissions at or above their current rate would very likely induce changes in the climate system larger than those observed in the 20th century.
In the IPCC Fourth Assessment Report, across a range of future emission scenarios, model-based estimates of sea level rise for the end of the 21st century (the year 2090-2099, relative to 1980-1999) range from 0.18 to 0.59 m. These estimates, however, were not given a likelihood due to a lack of scientific understanding, nor was an upper bound given for sea level rise. Over the course of centuries to millennia, the melting of ice sheets could result in sea level rise of 4–6 m or more.
Changes in regional climate are expected to include greater warming over land, with most warming at high northern latitudes, and least warming over the Southern Ocean and parts of the North Atlantic Ocean. Snow cover area and sea ice extent are expected to decrease. The frequency of hot extremes, heat waves, and heavy precipitation will very likely increase.
In terrestrial ecosystems, the earlier timing of spring events, and poleward and upward shifts in plant and animal ranges, have been linked with high confidence to recent warming. Future climate change is expected to particularly affect certain ecosystems, including tundra, mangroves, and coral reefs. It is expected that most ecosystems will be affected by higher atmospheric CO2 levels, combined with higher global temperatures. Overall, it is expected that climate change will result in the extinction of many species and reduced diversity of ecosystems.
Vulnerability of human societies to climate change mainly lies in the effects of extreme weather events rather than gradual climate change. Impacts of climate change so far include adverse effects on small islands, adverse effects on indigenous populations in high-latitude areas, and small but discernable effects on human health. Over the 21st century, climate change is likely to adversely affect hundreds of millions of people through increased coastal flooding, reductions in water supplies, increased malnutrition and increased health impacts.
Future warming of around 3 ?C (by 2100, relative to 1990-2000) could result in increased crop yields in mid- and high-latitude areas, but in low-latitude areas, yields could decline, increasing the risk of malnutrition. A similar regional pattern of net benefits and costs could occur for economic (market-sector) effects. Warming above 3 ?C could result in crop yields falling in temperate regions, leading to a reduction in global food production. Most economic studies suggest losses of world gross domestic product (GDP) for this magnitude of warming.
Reuters have reported that the US military is spending millions of dollars a year on nuclear submarine patrols and torpedo tests in the Arctic. This is with a view to global warming leading to Arctic ice disappearing during the summers from the mid-2030s onwards, which in turn will mean that they expect vast new oil and gas reserves to become accessible and commercial shipping to make increased use of shorter passages via the Bering Strait. They report that the US is "jockeying for position" with Russia, China, and other countries to benefit from such new business opportunities in the area.
Responses to global warming
Main article: Climate change mitigation
See also: Fee and dividend
Reducing the amount of future climate change is called mitigation of climate change. The IPCC defines mitigation as activities that reduce greenhouse gas (GHG) emissions, or enhance the capacity of carbon sinks to absorb GHGs from the atmosphere. Many countries, both developing and developed, are aiming to use cleaner, less polluting, technologies.:192 Use of these technologies aids mitigation and could result in substantial reductions in CO2 emissions. Policies include targets for emissions reductions, increased use of renewable energy, and increased energy efficiency. Studies indicate substantial potential for future reductions in emissions. Since even in the most optimistic scenario, fossil fuels are going to be used for years to come, mitigation may also involve carbon capture and storage, a process that traps CO2 produced by factories and gas or coal power stations and then stores it, usually underground.
Main article: Adaptation to global warming
Other policy responses include adaptation to climate change. Adaptation to climate change may be planned, e.g., by local or national government, or spontaneous, i.e., done privately without government intervention. The ability to adapt is closely linked to social and economic development. Even societies with high capacities to adapt are still vulnerable to climate change. Planned adaptation is already occurring on a limited basis. The barriers, limits, and costs of future adaptation are not fully understood.
Another policy response is engineering of the climate (geoengineering). This policy response is sometimes grouped together with mitigation. Geoengineering is largely unproven, and reliable cost estimates for it have not yet been published. Geoengineering encompasses a range of techniques to remove CO2 from the atmosphere or to block incoming sunlight. As most geoengineering techniques would affect the entire globe, the use of effective techniques, if they can be developed, would require global public acceptance and an adequate global legal and regulatory framework.
Most countries are Parties to the United Nations Framework Convention on Climate Change (UNFCCC). The ultimate objective of the Convention is to prevent "dangerous" human interference of the climate system. As is stated in the Convention, this requires that GHGs are stabilized in the atmosphere at a level where ecosystems can adapt naturally to climate change, food production is not threatened, and economic development can proceed in a sustainable fashion.
The UNFCCC recognizes differences among countries in their responsibility to act on climate change. In the Kyoto Protocol to the UNFCCC, most developed countries (listed in Annex I of the treaty) took on legally binding commitments to reduce their emissions. Policy measures taken in response to these commitments have reduced emissions. For many developing (non-Annex I) countries, reducing poverty is their overriding aim.
At the 15th UNFCCC Conference of the Parties, held in 2009 at Copenhagen, several UNFCCC Parties produced the Copenhagen Accord. Parties agreeing with the Accord aim to limit the future increase in global mean temperature to below 2 °C. The 16th Conference of the Parties (COP16) was held at Canc?n in 2010. It produced an agreement, not a binding treaty, that the Parties should take urgent action to reduce greenhouse gas emissions to meet the 2 °C goal. It also recognized the need to consider strengthening the goal to a global average rise of 1.5 °C.
Views on global warming
Main articles: Global warming controversy and Politics of global warming
See also: Scientific opinion on climate change and Public opinion on climate change
Per capita greenhouse gas emissions in 2005, including land-use change.
Total greenhouse gas emissions in 2005, including land-use change.
There are different views over what the appropriate policy response to climate change should be. These competing views weigh the benefits of limiting emissions of greenhouse gases against the costs. In general, it seems likely that climate change will impose greater damages and risks in poorer regions.
Developed and developing countries have made different arguments over who should bear the burden of economic costs for cutting emissions. Developing countries often concentrate on per capita emissions, that is, the total emissions of a country divided by its population. Per capita emissions in the industrialized countries are typically as much as ten times the average in developing countries. This is used to make the argument that the real problem of climate change is due to the profligate and unsustainable lifestyles of those living in rich countries.
On the other hand, Banuri et al. point out that total carbon emissions, carrying capacity, efficient energy use and civil and political rights are very important issues. Land is not the same everywhere. Not only the quantity of fossil fuel use but also the quality of energy use is a key debate point. Efficient energy use supporting technological change might help reduce excess carbon dioxide in Earth’s atmosphere. The use of fossil fuels for conspicuous consumption and excessive entertainment are issues that can conflict with civil and political rights. People in developed countries argue that history has proven the difficulty of implementing fair rationing programs in different countries because there is no global system of checks and balances or civil liberties.
The Kyoto Protocol, which came into force in 2005, sets legally binding emission limitations for most developed countries. Developing countries are not subject to limitations. This exemption led the U.S. and Australia to decide not to ratify the treaty,  although Australia did finally ratify the treaty in December 2007. Debate continued at the Copenhagen climate summit and the Canc?n climate summit.
In 2007–2008 Gallup Polls surveyed 127 countries. Over a third of the world’s population was unaware of global warming, with people in developing countries less aware than those in developed, and those in Africa the least aware. Of those aware, Latin America leads in belief that temperature changes are a result of human activities while Africa, parts of Asia and the Middle East, and a few countries from the Former Soviet Union lead in the opposite belief. In the Western world, opinions over the concept and the appropriate responses are divided. Nick Pidgeon of Cardiff University said that "results show the different stages of engagement about global warming on each side of the Atlantic", adding, "The debate in Europe is about what action needs to be taken, while many in the U.S. still debate whether climate change is happening." A 2010 poll by the Office of National Statistics found that 75% of UK respondents were at least "fairly convinced" that the world’s climate is changing, compared to 87% in a similar survey in 2006. A January 2011 ICM poll in the UK found 83% of respondents viewed climate change as a current or imminent threat, while 14% said it was no threat. Opinion was unchanged from an August 2009 poll asking the same question, though there had been a slight polarisation of opposing views.
A survey in October, 2009 by the Pew Research Center for the People & the Press showed decreasing public perception in the United States that global warming was a serious problem. All political persuasions showed reduced concern with lowest concern among Republicans, only 35% of whom considered there to be solid evidence of global warming. The cause of this marked difference in public opinion between the United States and the global public is uncertain but the hypothesis has been advanced that clearer communication by scientists both directly and through the media would be helpful in adequately informing the American public of the scientific consensus and the basis for it. The U.S. public appears to be unaware of the extent of scientific consensus regarding the issue, with 59% believing that scientists disagree "significantly" on global warming.
By 2010, with 111 countries surveyed, Gallup determined that there was a substantial decrease in the number of Americans and Europeans who viewed Global Warming as a serious threat. In the United States, a little over half the population (53%) now viewed it as a serious concern for either themselves or their families; a number 10 percentage points below the 2008 poll (63%). Latin America had the biggest rise in concern, with 73% saying global warming was a serious threat to their families.
Most scientists accept that humans are contributing to observed climate change. National science academies have called on world leaders for policies to cut global emissions. However, some scientists and non-scientists question aspects of climate-change science.
Organizations such as the libertarian Competitive Enterprise Institute, conservative commentators, and some companies such as ExxonMobil have challenged IPCC climate change scenarios, funded scientists who disagree with the scientific consensus, and provided their own projections of the economic cost of stricter controls. In the finance industry, Deutsche Bank has set up an institutional climate change investment division (DBCCA), which has commissioned and published research on the issues and debate surrounding global warming. Environmental organizations and public figures have emphasized changes in the current climate and the risks they entail, while promoting adaptation to changes in infrastructural needs and emissions reductions. Some fossil fuel companies have scaled back their efforts in recent years, or called for policies to reduce global warming.
The term global warming was probably first used in its modern sense on 8 August 1975 in a science paper by Wally Broecker in the journal Science called "Are we on the brink of a pronounced global warming?". Broecker’s choice of words was new and represented a significant recognition that the climate was warming; previously the phrasing used by scientists was "inadvertent climate modification," because while it was recognized humans could change the climate, no one was sure which direction it was going. The National Academy of Sciences first used global warming in a 1979 paper called the Charney Report, it said: "if carbon dioxide continues to increase, [we find] no reason to doubt that climate changes will result and no reason to believe that these changes will be negligible." The report made a distinction between referring to surface temperature changes as global warming, while referring to other changes caused by increased CO2 as climate change.
Global warming became more widely popular after 1988 when NASA climate scientist James Hansen used the term in a testimony to Congress. He said: "global warming has reached a level such that we can ascribe with a high degree of confidence a cause and effect relationship between the greenhouse effect and the observed warming." His testimony was widely reported and afterward global warming was commonly used by the press and in public discourse.
Air, is the most essential element for all living organisms and yet, most humans play a big role on polluting this essential resource. Air pollution may not be as dangerous in its direct outcome as nuclear or water pollution can be, but in the long term it will have an tremendous effect on the environment and health of its organisms living in. Asthma, cancer, acid rain, and the disability to photosynthesize are only a few causes of air pollution.The atmospheric pollutants with the greatest effect onto the environment are the carbon monoxide, carbon dioxide, hydrocarbons, sulfur dioxide, nitrogen oxides, dust particles, radioactive isotopes, and chlorofluorocarbons. The major sources that enable carbon monoxide to enter the atmosphere are the exhausts of cars, the burning of fossil fuels, and the oxidation of natural methane. Carbon dioxide is caused by the consumption of fossil fuels only and it causes the possible greenhouse effect which has global warming as an outcome. Hydrocarbons are caused by the combustion of oil and petrol and it effects the environment with carcinogen. Carcinogen is a chemical agent that causes cancer. Sulphur dioxide is certainly one of the major atmospheric pollutants considered that it causes stinging eyes, lung damage, asthma, and acid rain. It is the result of coal-fired power stations. Nitrogen oxides that is produced by the exhaust of cars, causes pneumonia and asphyxia. The outcome of the well known dust particles is often underestimated. It is caused by industrial chimneys, car exhaust, and volcanic eruptions and it effects the environment by toxic effects and damage of the lungs. Radioactive isotopes which are caused by small quantities from nuclear waste and nuclear accidents have an carcinogenic effect on the environment as well. The outcome of chlorfluorocarbons, which had been first discovered in the 80s is that it destroys the ozone layer. Many of those major atmospheric pollutants combined produce the dangerous and well known smoke and gas emission called smog.
Smog or dust dome is most often formed when a layer of cool air is trapped beneath a layer of still warmer air. The mixture of benzopyrene ( a cancer causing substance that is produced by the evaporation of petrol), the waste of hydrocarbons, combined with nitrogen dioxide, oxygen, and sunlight produce the photochemical smog which can be recognized as the yellow cloud over every big city in the world. Besides that optical effect it causes an increase of ozone in the lower atmosphere and the health conditions of the particular organism living in such an area. For example, it is estimated that “Washington DC receives 10% less sunlight than at the begging of the century due to the shielding of atmospheric pollution.” The ozone enters the leaves of plants turning them brown and makes it difficult for plant to photosynthesize. In addition to that, it causes skin cancer on humans. Most seriously though, it increases the acidity of the rain which is mainly caused by the rise of sulphur dioxide and nitrogen oxides that get caught up by clouds. All ready unpolluted rain is slightly acid due to dissolved carbon dioxide, but polluted rain may be very acidic. The effect of acid rain on terrestrial and aquatic ecosystems can be very different. “In Scandinavia, which receives a high proportion of its air pollution from Britain, once productive lakes are now completely devoid of fish.” In addition to its direct effect on water, acid rain allows metal ions such as aluminum, which is highly toxic to fish, to be leached from the soil . Acid rain reduces the growth of trees and disables plants to photosynthesize which destroys them in the long term. It also reduces the activity of nitrogen-fixing bacteria. In the event of a nuclear accident or war, the main risks do lay only partly in the pollution of air and air as a carrier of the polluted particles. The main risks arise from inhalation of contaminant particles, fallout of radioactive isotopes on soil with subsequent incorporation into food, and contamination of water supplies. The outcome of all those pollutant factors are enormous. The smoke from car engines which contains lead, that causes brain damage in children, stinging eyes, damage of the lung, the death rate of 40.000 asthma patients every year, and the destruction of whole forests includes only a few examples of the effects of air pollution. There are many ways to control and reduce air pollution and it is not the lack of technology but the unwillingness of the humans to change their attitudes and life styles.
It exists a wide range of technology for effective air pollution. Emissions of dust can and should be controlled by filters which remove solid particles before gases are discharged. Low sulphure fuels could be used in order to reduce the sulphure emission from coal-fired power stations. For all other forms of waste that get released during production into the air, technology provides a wide range of filters which are able to remove 80-95% of sulphur dioxide gas. The control of emission from the most common pollutant, the car, improvements can be made. The use of lead free patrol and catalytic converters would reduce toxic emissions to a fraction of their present level and prevent damage to the environment. Of course are the big companies the one which produce most waste and cause most pollution, but in order to change and reduce the air pollution, everyone, even the smallest household, needs to change its attitudes and be more responsible with the limited sources the nature is providing. If humans would be less greedy for money and willing to ensure a safe and clean environment for the children of tomorrow, vast improvements could be made that would be beneficial for the whole world.