''GLOBAL ISSUES''

       

Population growth rate[edit]

The "population growth rate" is the rate at which the number of individuals in a population increases in a given time period as a fraction of the initial population. Specifically, population growth rate refers to the change in population over a unit time period, often expressed as a percentageof the number of individuals in the population at the beginning of that period. This can be written as the formula:

A positive growth ratio (or rate) indicates that the population is increasing, while a negative growth ratio indicates the population is decreasing. A growth ratio of zero indicates that there were the same number of people at the two times—a growth rate may be zero even when there are significant changes in the birth rates, death rates, immigration rates, and age distribution between the two times.^[2]

A related measure is the net reproduction rate. In the absence of migration, a net reproduction rate of more than one indicates that the population of women is increasing, while a net reproduction rate less than one (sub-replacement fertility) indicates that the population of women is decreasing.

Human population growth rate[edit]

Main article: Total fertility rate

A world map showing global variations in fertility rate per woman, according to the CIA World Factbook's 2013 data.

7–8 children   6–7 children

5–6 children   4–5 children

3–4 children   2–3 children

1–2 children   0–1 children

Estimates of population evolution in different continentsbetween 1950 and 2050, according to the United Nations. The vertical axis is logarithmic and is in millions of people.

Growth rate of world population (1950–2050).

Globally, the growth rate of the human population has been declining since peaking in 1962 and 1963 at 2.20% per annum. In 2009, the estimated annual growth rate was 1.1%.^[3] The CIA World Factbook gives the world annual birthrate, mortality rate, and growth rate as 1.89%, 0.79%, and 1.096% respectively.^[4] The last 100 years have seen a rapid increase in population due to medical advances and massive increase in agricultural productivity^[5] made possible by the Green Revolution.^[6][7][8]

The actual annual growth in the number of humans fell from its peak of 88.0 million in 1989, to a low of 73.9 million in 2003, after which it rose again to 75.2 million in 2006. Since then, annual growth has declined. In 2009, the human population increased by 74.6 million, which is projected to fall steadily to about 41 million per annum in 2050, at which time the population will have increased to about 9.2 billion.^[3] Each region of the globe has seen great reductions in growth rate in recent decades, though growth rates remain above 2% in some countries of the Middle East and Sub-Saharan Africa, and also in South Asia, Southeast Asia, and Latin America.^[9]

Some countries experience negative population growth, especially in Eastern Europe mainly due to low fertility rates, high death rates and emigration. In Southern Africa, growth is slowing due to the high number of HIV-related deaths. Some Western Europe countries might also encounter negative population growth.^[10] Japan's population began decreasing in 2005.^[11] The United Nations Population Division expects world population to peak at over 10 billion at the end of the 21st century but Sanjeev Sanyal has argued that global fertility will fall below replacement rates in the 2020s and that world population will peak below 9 billion by 2050 followed by a long decline.^[12]

Growth by country[edit]

According to United Nations population statistics, the world population grew by 30%, or 1.6 billion people, between 1990 and 2010.^[13] In number of people the increase was highest in India 350 million and China 196 million. Population growth was among highest in the United Arab Emirates (315%) and Qatar (271%).^[13]

Growth rates of the world's most populous countries

Rank	Country	Population 2010	Population 1990	Growth (%) 1990–2010
	World	6,895,889,000	5,306,425,000	30.0%
1	China	1,341,335,000	1,145,195,000	17.1%
2	India	1,224,614,000	873,785,000	40.2%
3	United States	310,384,000	253,339,000	22.5%
4	Indonesia	239,871,000	184,346,000	30.1%
5	Brazil	194,946,000	149,650,000	30.3%
6	Pakistan	173,593,000	111,845,000	55.3%
7	Nigeria	158,423,000	97,552,000	62.4%
8	Bangladesh	148,692,000	105,256,000	41.3%
9	Russia	142,958,000	148,244,000	-3.6%
10	Japan	128,057,000	122,251,000	4.7%

'''ME AND MY FAMILY

     

                                                     THIS IS MY FAMILY

My family is the best of all they help me a lot and they are very supportive to me and help full. They teach me how to be brave on life. And my family is my inspiration to battle to life, many of us sometimes don't appreciate for what they are doing but for me even it is small thing but the important is its came from the heart. Family is my backbone on life i can't live without them, because without i don't think i can battle to life. My brother also who make me happy and brave, Thanks for my parents that they make me a better person a mature person that can his own decision but w/ there concern

global problem

          l global   warming 

Greenhouse GasesThe build-up of greenhouse gases in the atmosphere during the 20th century has resulted from the growing use of energy and 

expansion of the global economy. Over the century, industrial activity grew 40-fold, and the emissions of gases such as carbon dioxide (CO2) and sulphur dioxide (SO2) grew 10-fold.

The amount of CO2 in the air increased from some 280 parts per million by volume (ppmv) at the beginning of the century to 383 ppmv at the end of 2007. The amount of CO2 varies within each year as the result of the annual cycles of photosynthesis and oxidation (see graph). Of the other greenhouse gases, methane (CH4), which is formed by anaerobic decomposition of organic matter, rose from a preindustrial atmospheric concentration of around 700 parts per billion by volume (ppbv) to about 1 789 ppbv by 2007. Other important greenhouse gases include the oxides of nitrogen, notably nitrous oxide (NO2) and halocarbons, including the chlorofluorocarbons (CFCs) and other chlorine and bromine containing compounds.

The build-up of greenhouse gases in the atmosphere alters the radiative balance of the atmosphere. The net effect is to warm the Earth's surface and the lower atmosphere because greenhouse gases absorb some of the Earth’s outgoing heat radiation and reradiate it back towards the surface. The overall warming from 1850 to the end of the 20th century was equivalent to about 2.5 W/m2; CO2 contributed some 60 per cent of this figure and CH4about 25 per cent, with N2O and halocarbons providing the remainder. The warming effect that would result from a doubling of CO2 from pre-industrial levels is estimated to be 4 W/m2.

Ozone Depletion

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In 1985 Joe Farman, of the British Antarctic Survey, published a paper showing the decline of ozone levels over Antarctica during the early 1980s. The response was dramatic: large-scale international scientific programmes were mounted to prove that CFCs (used as aerosol propellants, in industrial cleaning fluids and in refrigeration equipment) were the cause of the problem. Even more important was immediate international action to curb the emissions of CFCs.

Plummeting ozone levels in the stratosphere over Antarctica during September and October are the result of complex chemical processes. The return of the Sun at the end of winter triggers photochemical reactions that lead to the destruction of ozone in the stratosphere. The October values of ozone have declined by up to 70 per cent compared to the pre-ozone hole years, and the size of the ozone hole had grown to more than 25 million km2 (twice the size of Antarctica) by 2000.

Over the Arctic the gradual development of an annual decline during the 1990s is a significant trend. More generally, over northern middle latitudes the concentration of stratospheric ozone has decreased since 1979 by 5.4 per cent in winter and spring, and by about 2.8 per cent in summer and autumn. There has been no discernible trend in the tropics and subtropics.

1. The scale and suddenness of the ozone decline shocked the scientific world, and led to the 1985 Vienna Convention for the Protection of the Ozone Layer and the 1987 Montreal Protocol and subsequent amendments to eliminate certain CFCs from industrial production. As a result of this rapid action the global consumption of the most active gases fell by 40 per cent within five years and the levels of certain chlorine-containing chemicals in the atmosphere have started to decline. It will be decades before the CFCs already in the atmosphere fully decay. In the meantime, the substantial destruction of ozone in the stratosphere over Antarctica during September and October will continue.

Aerosols in the Atmosphere

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Atmospheric aerosols are able to alter climate in two important ways. First, they scatter and absorb solar and infrared radiation and, second, they may change the microphysical and chemical properties of clouds and possibly their lifetime and extent. The scattering of solar radiation acts to cool the planet, while absorption of solar radiation by aerosols warms the air directly instead of allowing sunlight to be absorbed by the surface of the Earth.

The human contribution to the amount of aerosols in the atmosphere takes many forms. Dust is a biproduct of agriculture. Biomass burning produces a combination of organic droplets and soot particles. Industrial processes produce a wide variety of aerosols depending on what is being burned or produced in the manufacturing process. In addition, exhaust emissions from transport generate a rich cocktail of pollutants that are either aerosols from the outset, or are converted by chemical reactions in the atmosphere to form aerosols.

The concentrations of condensation nuclei are about three times higher in the Northern Hemisphere than in the Southern Hemisphere. This higher concentration is estimated to result in radiation forcing that is only about 50 per cent higher for the Northern Hemisphere.