Chlorofluorocarbons (CFCs)

Chlorofluorocarbons (CFCs) are nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine. They are used in the manufacture of aerosol sprays, blowing agents for foams and packing materials, as solvents, and as refrigerants. CFCs are classified as halocarbons, a class of compounds that contain atoms of carbon and halogen atoms. Individual CFC molecules are labeled with a unique numbering system. For example, the CFC number of 11 indicates the number of atoms of carbon, hydrogen, fluorine, and chlorine (e.g. CCl₃F as CFC-11). The best way to remember the system is the "rule of 90" or add 90 to the CFC number where the first digit is the number of carbon atoms (C), the second digit is the number of hydrogen atoms (H), and the third digit is number of the fluorine atoms (F). The total number of chlorine atoms (Cl) are calculated by the expression: Cl = 2(C+1) - H - F. In the example CFC-11 has one carbon, no hydrogen, one fluorine, and therefore 3 chlorine atoms.

Refrigerators in the late 1800s and early 1900s used the toxic gases, ammonia (NH₃), methyl chloride (CH₃Cl), and sulfur dioxide (SO₂), as refrigerants. After a series of fatal accidents in the 1920s when methyl chloride leaked out of refrigerators, a search for a less toxic replacement begun as a collaborative effort of three American corporations- Frigidaire, General Motors, and Du Pont. CFCs were first synthesized in 1928 by Thomas Midgley, Jr. of General Motors, as safer chemicals for refrigerators used in large commercial appilications¹. Frigidaire was issued the first patent, number 1,886,339, for the formula for CFCs on December 31, 1928. In 1930, General Motors and Du Pont formed the Kinetic Chemical Company to produce Freon (a Du Pont tradename for CFCs) in large quantities. By 1935 Frigidaire and its competitors had sold 8 million new refrigerators in the United States using Freon-12 (CFC-12) made by the Kinetic Chemical Company and those companies that were licensed to manufacture this compound. In 1932 the Carrier Engineering Corporation used Freon-11 (CFC-11) in the worldís first self-contained home air-conditioning unit, called the "Atmospheric Cabinet".; Because of the CFC safety record for nontoxicity, Freon became the preferred coolant in large air-conditioning systems. Public health codes in many American cities were revised to designate Freon as the only coolant that could be used in public buildings. After World War II, CFCs were used as propellants for bug sprays, paints, hair conditioners, and other health care products. During the late 1950s and early 1960s the CFCs made possible an inexpensive solution to the desire for air conditioning in many automobiles, homes, and office buildings. Later, the growth in CFC use took off worldwide with peak, annual sales of about a billion dollars (U.S.) and more than one million metric tons of CFCs produced.

Whereas CFCs are safe to use in most applications and are inert in the lower atmosphere, they do undergo significant reaction in the upper atmosphere or stratosphere. In 1974, two University of California chemists, Professor F. Sherwood Rowland and Dr. Mario Molina, showed that the CFCs could be a major source of inorganic chlorine in the stratosphere following their photolytic decomposition by UV radiation. In addition, some of the released chlorine would become active in destroying ozone in the stratosphere². Ozone is a trace gas located primarily in the stratosphere (see ozone). Ozone absorbs harmful ultraviolet radiation in the wavelengths between 280 and 320 nm of the UV-B band which can cause biological damage in plants and animals. A loss of stratospheric ozone results in more harmful UV-B radiation reaching the Earth's surface. Chlorine released from CFCs destroys ozone in catalytic reactions where 100,000 molecules of ozone can be destroyed per chlorine atom.

A large springtime depletion of stratospheric ozone was getting worse each following year. This ozone loss was described in 1985 by British researcher Joe Farman and his colleagues³. It was called ìthe Antarctic ozone holeî by others. The ozone hole was different than ozone loss in the midlatitudes. The loss was greater over Antarctic than the midlatitudes because of many factors: the unusually cold temperatures of the region, the dynamic isolation of this ìholeî, and the synergistic reactions of chlorine and bromine⁴. Ozone loss also is enhanced in polar regions as a result of reactions involving polar stratospheric clouds (PSCs)⁵ and in midlatitudes following volcanic eruptions. The need for controlling the CFCs became urgent.

In 1987, 27 nations signed a global environmental treaty, the Montreal Protocol to Reduce Substances that Deplete the Ozone Layer⁶, that had a provision to reduce 1986 production levels of these compounds by 50% before the year 2000. This international agreement included restrictions on production of CFC-11, -12, -113, -114, -115, and the Halons (chemicals used as a fire extinguishing agents). An amendment approved in London in 1990 was more forceful and called for the elimination of production by the year 2000. The chlorinated solvents, methyl chloroform (CH₃CCl₃), and carbon tetrachloride (CCl₄) were added to the London Amendment.

Large amounts of reactive stratospheric chlorine in the form of chlorine monoxide (ClO) that could only result from the destruction of ozone by the CFCs in the stratosphere were observed by instruments onboard the NASA ER-2 aircraft and UARS (Upper Atmospheric Research Satellite) over some regions in North America during the winter of 1992^7,8. The environmental concern for CFCs follows from their long atmospheric lifetime (55 years for CFC-11 and 140 years for CFC-12, CCl₂F₂)⁹ which limits our ability to reduce their abundance in the atmosphere and associated future ozone loss. This resulted in the Copenhagen Amendment that further limited production and was approved later in 1992. The manufacture of these chemicals ended for the most part on January 1, 1996. The only exceptions approved were for production within developing countries and for some exempted applications in medicine (i.e., asthma inhalators) and research. The Montreal Protocol included enforcement provisions by applying economic and trade penalties should a signatory country trade or produce these banned chemicals. A total of 148 signatory countries have now signed the Montreal Protocol. Atmospheric measurements CFC-11 and CFC-12 reported in 1993 showed that their growth rates were decreasing as result of both voluntary and mandated reductions in emissions⁹. Many CFCs and selected chlorinated solvents have either leveled off (Figure 1) or decreased in concentration by 1994^9,10.

The demand for the CFCs was accomodated by recycling, and reuse of existing stocks of CFCs and by the use of substitutes. Some applications, for example degreasing of metals and cleaning solvents for circuit boards, that once used CFCs now use halocarbon-free fluids, water (sometimes as steam), and diluted citric acids. Industry developed two classes of halocarbon substitutes- the hydrochlorofluorocarbons (HCFCs) and the hydrofluorocarbons (HFCs). The HCFCs include hydrogen atoms in addition to chlorine, fluorine, and carbon atoms. The advantage of using HCFCs is that the hydrogen reacts with tropospheric hydroxyl (OH), resulting in a shorter atmospheric lifetime. HCFC-22 (CHClF₂) has an atmospheric lifetime of about 13 years¹¹ and has been used in low-demand home air-conditioning and some refrigeration applications since 1975. However, HCFCs still contain chlorine which makes it possible for them to destroy ozone. The Copenhagen amendment calls for their production to be eliminated by the year 2030. The HFCs are considered one of the best substitutes for reducing stratospheric ozone loss because of their short lifetime and lack of chlorine. In the United States, HFC-134a is used in all new domestic automobile air conditioners. For example, HFC-134a is growing rapidly in 1995 at a growth rate of about 100% per year with an atmospheric lifetime of about 12 years¹². (The "rule of 90" also applies for the chemical formula of HCFCs and HFCs.)

Use of the CFCs, some chlorinated solvents, and Halons should become obsolete in the next decade if the Montreal Protocol is observed by all parties and substitutes are used. The science that became the basis for the Montreal Protocol resulted in the 1995 Nobel Prize for Chemistry. The prize was awarded jointly to Professors F. S. Rowland at University of California at Irvine, M. Molina at the Massachusetts Institute of Technology, Cambridge, and Paul Crutzen at the Max-Planck-Institute for Chemistry in Mainz, Germany, for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone (in particular, by the CFCs and oxides of nitrogen).

¹Midgley, T., and Henne, A., Organic fluorides as refrigerants, Industrial and Engineering Chemistry, 22, 542-547, 1930.

²Molina, M.J., and F.S. Rowland, Stratospheric sink for chlorofluoromethanes: Chlorine atom catalyzed destruction of ozone, Nature, 249, 810-814, 1974.

³Farman, J.C., B.G. Gardiner, and J.D. Shanklin, Large losses of total ozone in Antarctica reveal seasonal ClOx/NOx interaction, Nature, 315,207-210, 1985.

⁴McElroy, M.B., R.J. Salawitch, S.C. Wofsy, and J.A. Logan, Reductions of Antarctic ozone due to synergistic interactions of chlorine and bromine, Nature, 321, 759-762, 1986.

⁵Solomon, S., R.R. Garcia, F.S. Rowland, and D.J. Wuebbles, On the depletion of Antarctic ozone, Nature, 321, 755-758, 1986.

⁶Montreal Protocol on Substances that Deplete the Ozone Layer, 15 pp, United Nations Environmental Programme (UNEP), New York, 1987.

⁷Toohey, D.W., L.M. Avallone, L.R. Lait, P.A. Newman, M.R. Schoeberl, D.W. Fahey, E.L. Woodbridge, and J.G. Anderson, The seasonal evolution of reactive chlorine in the northern hemisphere stratosphere, Science, 261, 1134-1136, 1993.

⁸Waters, J., L. Froidevaux, W. Read, G. Manney, L. .Elson, D. Flower, R. Jarnot, and R. Harwood, Stratospheric ClO andozone from the Microwave Limb Sounder on the Upper Atmosphere Research Satellite, Nature, 362, 597-602, 1993.

⁹Elkins, J.W., T.M. Thompson, T.H. Swanson, J.H. Butler, B.D. Hall, S.O. Cummings, D.A. Fisher, and A.G. Raffo, Decrease in the growth rates of atmospheric chlorofluorocarbons 11 and 12, Nature, 364 , 780-783, 1993.

¹⁰Prinn, R.G., R.F. Weiss, B.R. Miller, J. Huang, F.N. Alyea, D.M. Cunnold, P.J. Fraser, D.E. Hartley, and P.G. Simmonds, Atmospheric trends and lifetimes of CH₃CCl₃ and global OH concentrations, Science, 269, 187-192, 1995.

¹¹Montzka, S.A., R.C. Myers, J.H. Butler, S.C. Cummings, and J.W. Elkins, Global tropospheric distribution and calibration scale of HCFC-22, Geophysical Research Letters, 20(8), 703-706, 1993.

¹²Montzka, S.A., R.C. Myers, J.H. Butler, J.W. Elkins, L.T. Lock, A.D. Clarke, and A.H. Goldstein, Observations of HFC-134a in the remote troposphere, Geophysical Research Letters, 23, 169-172, 1996.

Suggested Additional Reading:

Cagin, S., and P. Dray, Between Earth and Sky: How CFCs changed our world and threatened the ozone layer, 512 pp., Pantheon Press, New York, 1993.

Scientific Assessment of Ozone Depletion: 1994, edited by D. L. Albritton, R. T. Watson, and R. J. Aucamp, 37, 451 pp., World Meteorological Organization (WMO), Geneva, 1995.

Figure 1: The accumulation of chlorofluorocarbon-11 (CFC-11) in the atmosphere levels off as a result of voluntary and mandated emission reductions. Monthly means reported as dry mixing ratios in parts per trillion (ppt) for CFC-11 at ground level for four NOAA/CMDL stations (Pt. Barrow, Alaska; Mauna Loa, Hawaii; Cape Matatula, American Samoa; and South Pole) and three cooperative stations (Alert, Northwest Territories, Canada (Atmospheric Environment Service); Niwot Ridge, Colorado (University of Colorado); Cape Grim Baseline Air Pollution Station, Tasmania, Australia, (Commonwealth Scientific and Industrial Research Organization)⁹. (Courtesy of NOAA/CMDL)

Source:  www.esrl.noaa.gov

Green House Effect

A representation of the exchanges of energy between the source (theSun), Earth's surface, the Earth's atmosphere, and the ultimate sinkouter space. The ability of the atmosphere to capture and recycle energy emitted by Earth's surface is the defining characteristic of the greenhouse effect.

Another diagram of the greenhouse effect

The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere.^[1][2]

If a planet's atmosphere contains radiatively active gases (i.e., greenhouse gases) the atmosphere will radiate energy in all directions. Part of this radiation is directed towards the surface, warming it. The downward component of this radiation – that is, the strength of the greenhouse effect – will depend on the atmosphere's temperature and on the amount of greenhouse gases that the atmosphere contains.

On Earth, the atmosphere is warmed by absorption of infrared thermal radiation from the underlying surface, absorption of shorter wavelength radiant energy from the sun, and convective heat fluxes from the surface. Greenhouse gases in the atmosphere radiate energy, some of which is directed to the surface and lower atmosphere. The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.^[3]

Earth’s natural greenhouse effect is critical to supporting life. Human activities, primarily the burning of fossil fuels and clearing of forests, have intensified the natural greenhouse effect, causing global warming.^[4]

The mechanism is named after a faulty analogy with the effect of solar radiation passing through glass and warming a greenhouse. The way a greenhouse retains heat is fundamentally different, as a greenhouse works by reducing airflow and retaining warm air inside the structure.

Source: Wikipedia

Ozone FAQ

What is the ozone layer and why is it important?

The ozone layer is a concentration of ozone molecules in the stratosphere. About 90% of the planet's ozone is in the ozone layer. The layer of the Earth's atmosphere that surrounds us is called the troposphere. The stratosphere, the next higher layer, extends about 10–50 kilometers above the Earth's surface. Stratospheric ozone is a naturally occurring gas that filters the sun's ultraviolet (UV) radiation. A diminished ozone layer allows more radiation to reach the Earth's surface. For people, overexposure to UV rays can lead to skin cancer, cataracts, and weakened immune systems. Increased UV can also lead to reduced crop yield, disruptions in the marine food chain, and other harmful effects.

How does ozone depletion occur?

It is caused by the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances (ODS), which were used widely as refrigerants, insulating foams, and solvents. The discussion below focuses on CFCs, but is relevant to all ODS. Although CFCs are heavier than air, they are eventually carried into the stratosphere in a process that can take as long as 2 to 5 years.

When CFCs reach the stratosphere, the ultraviolet radiation from the sun causes them to break apart and release chlorine atoms, which react with ozone, starting chemical cycles of ozone destruction that deplete the ozone layer. One chlorine atom can break apart more than 100,000 ozone molecules.

Other chemicals that damage the ozone layer include methyl bromide (used as a pesticide) and halons (used in fire extinguishers). As methyl bromide and halons are broken apart, they release bromine atoms, which are 40 times more destructive to ozone molecules than chlorine atoms.

How do we know that natural sources are not responsible for ozone depletion?

While it is true that volcanoes and oceans release large amounts of chlorine, the chlorine from these sources is easily dissolved in water and washes out of the atmosphere in rain. In contrast, CFCs are not broken down in the lower atmosphere and do not dissolve in water. The chlorine in these human-made molecules does reach the stratosphere. Measurements show that the increase in stratospheric chlorine since 1985 matches the amount released from CFCs and other ozone-depleting substances produced and released by human activities.

What is being done about ozone depletion?

In 1978, the use of CFC propellants in spray cans was banned in the U.S. In the 1980s, the Antarctic “ozone hole” appeared and an international science assessment more strongly linked the release of CFCs and ozone depletion. It became evident that a stronger worldwide response was needed. In 1987, the Montreal Protocol was signed and the signatory nations committed themselves to a reduction in the use of CFCs and other ozone-depleting substances.

Since that time, the treaty has been amended to ban CFC production after 1995 in the developed countries, and later in developing. Today, over 160 countries have signed the treaty. Beginning January 1, 1996, only recycled and stockpiled CFCs will be available for use in developed countries like the US. This production phaseout is possible because of efforts to ensure that there will be substitute chemicals and technologies for all CFC uses.

Will the ozone layer recover? Can we make more ozone to fill in the hole?

The answers, in order, are: yes and no. We can't make enough ozone to replace what's been destroyed, but provided that we stop producing ozone-depleting substances, natural ozone production reactions should return the ozone layer to normal levels by about 2050. It is very important that the world comply with the Montreal Protocol; delays in ending production could result in additional damage and prolong the ozone layer's recovery.

Source:www.factmonster.com

The Ozone Layer & Ozone Depletion

The Earth's atmosphere is divided into several layers. The lowest region, the troposphere, extends from the Earth's surface up to about 10 kilometers (km) in altitude. The next layer, the stratosphere, continues from 10 km to about 50 km. Most atmospheric ozone is concentrated in a layer in the stratosphere, about 15–30 kilometers above the Earth's surface.

Ozone is a molecule containing three oxygen atoms. It is blue in color and has a strong odor. Normal oxygen, which we breathe, has two oxygen atoms and is colorless and odorless. Ozone is much less common than normal oxygen. Out of each 10 million air molecules, about 2 million are normal oxygen, but only 3 are ozone.

However, even the small amount of ozone plays a key role in the atmosphere. The ozone layer absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface. Most importantly, it absorbs the portion of ultraviolet light called UVB. UVB has been linked to many harmful effects, including various types of skin cancer, cataracts, and harm to some crops, certain materials, and some forms of marine life.

At any given time, ozone molecules are constantly formed and destroyed in the stratosphere. The total amount, however, remains relatively stable. While ozone concentrations vary naturally with sunspots, the seasons, and latitude, these processes are well understood and predictable. Each natural reduction in ozone levels has been followed by a recovery. Recently, however, convincing scientific evidence has shown that the ozone shield is being depleted well beyond changes due to natural processes.

What is the limitation of the Mankind

I have found from my planning and scheduling experience that weaknesses and limitation of manpower planning are usually these:

• Most companies never make use of the potential of all of their manpower. A few people are assigned the majority of the work and the remainder either pick up any slack or are used a "filler" for minor tasks or absenteeism. Planners and schedulers are asked to compensate for this and don't always do a good job accordingly.
• You can't "plan" for people not showing up. Illness,injury, accidents,etc happen. No amount of planning can compensate for them and as a result many manpower plans are limited because of those contingencies.
• Your plans have to incorporate the fact that large numbers of employees might have deficiencies in skill or education. While this can be offset somewhat by training in the pre-planning stages, most companies want larger numbers of skilled workers than are available on the market at any given time. They also want them geographically close and willing to work for a set amount of money.
• If you are planning projects in tight labor markets, you often find that you have scale back your planning accordingly as their simply aren't enough people for your projects. A company might need 100 workers, but due to low unemployment in the area (yes, there are places where this is a problem) they have to settle for 50-75 just to begin their project.
• Wages - Some companies simply have a set amount they want to pay employees,regardless of whether or not that rate is competitive in their market. As a result, unless economic times are dire, most manpower planners have to compensate for the fewer applicants that will apply for these positions and the fewer that will remain when they are able to obtain better offers.

Source: www.quora.com

Pollution of water

As technology improves, scientists are able to detect more pollutants, and at smaller concentrations, in Earth’s freshwater bodies. Containing traces of contaminants ranging from birth control pills and sunscreen to pesticides and petroleum, our planet's lakes, rivers, streams, and groundwater are often a chemical cocktail.

Beyond synthetic pollution, freshwater is also the end point for biological waste, in the form of human sewage, animal excrement, and rainwater runoff flavored by nutrient-rich fertilizers from yards and farms. These nutrients find their way through river systems into seas, sometimes creating coastal ocean zones void of oxygen—and therefore aquatic life—and making the connection between land and sea painfully obvious. When you dump paint down the drain, it often ends up in the ocean, via freshwater systems.

In the developed world, regulation has restricted industry and agricultural operations from pouring pollutants into lakes, streams, and rivers. Technology has also offered a solution in the form of expensive filtration and treatment plants that make our drinking water safe to consume. Some cities are even promoting "green" infrastructure, such as green roofs and rain gardens, as a way to naturally filter out pollutants. But you may find a different picture in parts of the developing world, where there is less infrastructure—politically, economically, and technically—to deal with the barrage of pollution threats facing freshwater and all of the species that rely on it.

Fast Facts

• In developing countries, 70 percent of industrial wastes are dumped untreated into waters, polluting the usable water supply.

• On average, 99 million pounds (45 million kilograms) of fertilizers and chemicals are used each year.

• Portland, Oregon, is actively pursing “green roofs” and “green streets” to prevent sewer overflows into the Willamette River. Chicago, Illinois, now has more than 517,000 acres (209,222 hectares) of vegetated roofs—more than any other U.S. city—which are helping to catch storm water, cool the urban environment, and provide opportunities for rooftop gardens.

Source:nationalgeographic.com

Noise Pollution Takes Toll on Health and Happiness

Noise Pollution takes toll on health and Happiness of our life

In the beginning there was silence, and it was good.

From silence came sound, not all of which was good. And the sound that was not welcome was called noise. And there got to be more and more of it, because who wants to rake when you can blow?
Let me be honest. I don't get along with noise. I see it, or rather hear it, as the essayist Ambrose Bierce did around the turn of the last century: as "a stench in the ear."
And by "noise" I don't mean only the noises that everyone agrees are bad for your hearing -- those ear-splitting sirens and the stand-right-next-to-the-speaker heavy metal concerts. Even everyday noise eats away at my nerves.
You may say I'm thin-skinned, but I have science on my side. A growing body of evidence confirms that the chronic din of construction crews, road projects, jet traffic and, yes, those ubiquitous leaf blowers, is taking a toll on our health and happiness.

Providing scientific proof of this has not been easy -- in part because noise, defined as "unwanted sound," is to a large degree a matter of personal taste and sensitivity. The romantic hears a train whistle differently from the insomniac. And no small number of Americans pay good money to hear the same rock-and-roll music that was used to torture the holed-up Panamanian dictator, Manuel Noriega, and Waco's David Koresh and induce cooperation from prisoners in Iraq and Guantanamo Bay, Cuba.
But study after study has found that community noise is interrupting our sleep, interfering with our children's learning, suppressing our immune systems and even increasing -- albeit just a little -- our chances of having a heart attack. It is also tarnishing the Golden Rule, reducing people's inclination to help one another.
"Everyday noise is under the radar, yet it affects everyone's life," said Louis Hagler, a retired physician in Oakland, Calif., and an advocate for quiet, who recently published in the Southern Medical Journal a review of studies linking noise exposures to health problems. "We don't say to people, 'You just have to learn to live with sewage in your water,' " Hagler said in an interview. "Why should we tolerate sewage coming into our ears?"
As I write -- from home today, the better to concentrate, I told my editor -- there is a person up the street blowing leaves and dust from one part of his property to another. To accomplish this task, he is generating a sound that is only a little less intense than the 85 decibels that the National Institute of Occupational Safety and Health says is physically damaging over a period of hours, and more than loud enough to make it almost impossible for me to think.
Leaf blowers may be my pet peeve, but it is modern transportation -- cars, motorcycles, trucks and air traffic -- that accounts for most of the background noise that disturbs and even sickens people.
More than 40 percent of Americans whose homes have any traffic noise at all classify that noise as "bothersome," according to the 2005 American Housing Survey, conducted by the U.S. Census Bureau. One-third of those say the noise is so bothersome they want to move. All told, more than 100 million Americans are regularly exposed to noise levels in excess of the 55 decibels that federal agencies have recommended as a reasonable background intensity.
Here in the Washington area, a battle over airport noise is posed to erupt this summer as the Senate considers adding as many as 20 new daily takeoffs and landings at Reagan National, a move opposed by neighbors already fed up with the steady roar of low-flying jets.

Source:www.washingtonpost.com

Plants and Animal & Social effects

The effects of global warming on the Earth's ecosystems are expected to be profound and widespread. Many species of plants and animals are already moving their range northward or to higher altitudes as a result of warming temperatures, according to a report from the National Academy of Sciences.

"They are not just moving north, they are moving from the equator toward the poles. They are quite simply following the range of comfortable temperatures, which is migrating to the poles as the global average temperature warms," Werne said. Ultimately, he said, this becomes a problem when the rate of climate change velocity (how fast a region changes put into a spatial term) is faster than the rate that many organisms can migrate. Because of this, many animals may not be able to compete in the new climate regime and may go extinct.

Additionally, migratory birds and insects are now arriving in their summer feeding and nesting grounds several days or weeks earlier than they did in the 20th century, according to the EPA.

Warmer temperatures will also expand the range of many disease-causing pathogens that were once confined to tropical and subtropical areas, killing off plant and animal species that formerly were protected from disease.

These and other effects of global warming, if left unchecked, will likely contribute to the disappearance of up to one-half of Earth's plants and one-third of animals from their current range by 2080, according to a 2013 report in the journal Nature Climate Change.

As dramatic as the effects of climate change are expected to be on the natural world, the projected changes to human society may be even more devastating.

Agricultural systems will likely be dealt a crippling blow. Though growing seasons in some areas will expand, the combined impacts of drought, severe weather, lack of snowmelt, greater number and diversity of pests, lower groundwater tables and a loss of arable land could cause severe crop failures and livestock shortages worldwide.

North Carolina State University also notes that carbon dioxide is affecting plant growth. Though CO₂ can increase the growth of plants, the plants may become less nutritious.

In addition to less nutritious food, the effect of global warming on human health is also expected to be serious. The American Medical Association has reported an increase in mosquito-borne diseases like malaria and dengue fever, as well as a rise in cases of chronic conditions like asthma, are already occurring, most likely as a direct result of global warming.

This loss of food security may, in turn, create havoc in international food markets and could spark famines, food riots, political instability and civil unrest worldwide, according to a number of analyses from sources as diverse as the U.S Department of Defense, the Center for American Progress and the Woodrow Wilson International Center for Scholars.

Many of these expected effects are the result of exhaustive scientific research and climate models, and the fact that most of them are already being observed gives additional credibility to the projected effects of global warming and climate change.
Source:www.livescience.com

Global warming is expected in all places

Global warming is expected to have far-reaching, long-lasting and, in many cases, devastating consequences for planet Earth.

For some years, global warming, the gradual heating of Earth's surface, oceans and atmosphere, was a topic of heated debate in the scientific community. Today, the overwhelming consensus of researchers is that global warming is real and is caused by human activity, primarily the burning of fossil fuels that pump carbon dioxide (CO₂), methane and other greenhouse gases into the atmosphere.

A major report released Sept. 27, 2013, by the Intergovernmental Panel on Climate Change (IPCC) stated that scientists are more certain than ever of the link between human activities and global warming. More than 197 international scientific organizations agree that global warming is real and has been caused by human action.

Additionally, global warming is having a measurable effect on the planet right now, in a variety of ways. "We can observe this happening in real time in many places. Ice is melting in both polar ice caps and mountain glaciers. Lakes around the world, including Lake Superior, are warming rapidly – in some cases faster than the surrounding environment. Animals are changing migration patterns and plants are changing the dates of activity (e.g., leaf-flush in spring to fall in autumn is longer)," Josef Werne, an associate professor in the department of geology and planetary science at the University of Pittsburgh, told Live Science.

Here is an in-depth look at these changes and more.

Increase in average temperatures and temperature extremes

One of the most immediate and obvious effects of global warming is the increase in temperatures around the world. The average global temperature has increased by about 1.4 degrees Fahrenheit (0.8 degrees Celsius) over the past 100 years, according to the National Oceanic and Atmospheric Administration (NOAA).

Since recordkeeping began in 1895, the hottest year on record for the 48 contiguous U.S. states was 2012. Worldwide, 2012 was also the 10th-warmest year on record, according to NOAA. And nine of the warmest years on record have occurred since 2000. According to NOAA, 2013 tied with 2003 as the fourth warmest year globally since 1880.

In 2014, some cities in the United States had the warmest summers on record, according to Scientific American. A report by the World Meteorological Organization released July 3, 2014, said that deaths from heat increased by more than 2,000 percent over the previous decade.

Extreme weather events

Extreme weather is an effect of global warming. While experiencing some of the hottest summers on record, much of the United States also has been experiencing colder than normal winters.

Changes in climate can cause the jet stream to migrate south, bringing with it cold, Arctic air. This is why some states can have a sudden cold snap or colder than normal winter, even during the long-term trend of global warming, Werne explained.

"Climate is by definition the long-term average of weather, over many years. One cold (or warm) year or season has little to do with overall climate. It is when those cold (or warm) years become more and more regular that we start to recognize it as a change in climate rather than simply an anomalous year of weather," he said.

Global warming may also lead to extreme weather other than cold or heat extremes. For example, hurricane formations will change. Though this is still a subject of active scientific research, current computer models of the atmosphere indicate that hurricanes are more likely to become less frequent on a global basis, though the hurricanes that do form may be more intense.

"And even if they become less frequent globally, hurricanes could still become more frequent in some particular areas," said atmospheric scientist Adam Sobel, author of "Storm Surge: Hurricane Sandy, Our Changing Climate, and Extreme Weather of the Past and Future" (HarperWave, 2014). "Additionally, scientists are confident that hurricanes will become more intense due to climate change."  This is because hurricanes get their energy from the temperature difference between the warm tropical ocean and the cold upper atmosphere. Global warming increases that temperature difference. 

"Since the most damage by far comes from the most intense hurricanes — such as typhoon Haiyan in the Philippines in 2013 — this means that hurricanes could become overall more destructive," said Sobel, a Columbia University professor in the departments of Earth and Environmental Sciences, and Applied Physics and Applied Mathematics.

Lightening is another weather feature that is being affected by global warming. According to a 2014 study, a 50 percent increase in the number of lightning strikes within the United States is expected by 2100 if global temperatures continue to rise. The researchers of the study found a 12 percent increase in lightning activity for every 1.8 degree F (1 degree C) of warming in the atmosphere.

The U.S. Climate Extremes Index (CEI) was established in 1996 to track extreme weather events. The number of extreme weather events that are among the most unusual in the historical record, according to the CEI, has been rising over the last four decades.

Scientists project that extreme weather events, such as heat waves, droughts, blizzards and rainstorms will continue to occur more often and with greater intensity due to global warming, according to Climate Central. Climate models forecast that global warming will cause climate patterns worldwide to experience significant changes. These changes will likely include major shifts in wind patterns, annual precipitation and seasonal temperatures variations.

In addition, because high levels of greenhouse gases in the atmosphere are likely to remain high for many years, these changes are expected to last for several decades or longer, according to the Environmental Protection Agency (EPA). In the northeastern United States, for example, climate change is likely to bring increased annual rainfall, while in the Pacific Northwest, summer rainfall is expected to decrease. lake sits at the left-hand terminus of the glacier. Taken in Thomsen Land, northeast Greenland. 

Source:www.livescience.com