GLOBAL WARMING

GLOBAL WARMING

INTRODUCTION:
Global warming is the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.
The global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 years ending in 2005.[1] The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations"[1] via the greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.[2][3] These basic conclusions have been endorsed by at least 30 scientific societies and academies of science,[4] including all of the national academies of science of the major industrialized countries.[5][6][7] While individual scientists have voiced disagreement with some findings of the IPCC,[8] the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.[9][10]
Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the 21st century.[1] The range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.[1]
Increasing global temperature will cause sea level to rise, and is expected to increase the intensity of extreme weather events and to change the amount and pattern of precipitation. Other effects of global warming include changes in agricultural yields, trade routes, glacier retreat, species extinctions and increases in the ranges of disease vectors.
Remaining scientific uncertainties include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions, but there is ongoing political and public debate worldwide regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences.

EFFECTS OF GLOBAL WARMING:
The predicted effects of global warming on the environment and for human life are numerous and varied. It is generally difficult to attribute specific natural phenomena to long-term causes, but some effects of recent climate change may already be occurring. Rising sea levels, glacier retreat, Arctic shrinkage, and altered patterns of agriculture are cited as direct consequences, but predictions for secondary and regional effects include extreme weather events, an expansion of tropical diseases, changes in the timing of seasonal patterns in ecosystems, and drastic economic impact. Concerns have led to political activism advocating proposals to mitigate, eliminate, or adapt to it.
The 2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC) includes a summary of the expected effects.

CAUSES
Components of the current radiative forcing as estimated by the IPCC Fourth Assessment Report.
Main articles:
Attribution of recent climate change and Scientific opinion on climate change.
The Earth's climate changes in response to external forcing, including variations in its orbit around the Sun (orbital forcing),[13][14][15] volcanic eruptions,[16] and atmospheric greenhouse gas concentrations. The detailed causes of the recent warming remain an active field of research, but the scientific consensus[17][18] is that the increase in atmospheric greenhouse gases due to human activity caused most of the warming observed since the start of the industrial era. This attribution is clearest for the most recent 50 years, for which the most detailed data are available. Some other hypotheses departing from the consensus view have been suggested to explain the temperature increase. One such hypothesis proposes that warming may be the result of variations in solar activity.
None of the effects of forcing are instantaneous. The thermal inertia of the Earth's oceans and slow responses of other indirect effects mean that the Earth's current climate is not in equilibrium with the forcing imposed. 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.

GREENHOUSE GASES IN THE ATMOSPHERE
Main articles: Greenhouse gas and Greenhouse effect
The greenhouse effect was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896. It is the process by which absorption and emission of infrared radiation by atmospheric gases warm a planet's lower atmosphere and surface.
Existence of the greenhouse effect as such is not disputed. Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F), without which Earth would be uninhabitable.[23][24] Rather, the issue is how the strength of the greenhouse effect changes when human activity increases the atmospheric concentrations of some greenhouse gases.
On Earth, the major greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect (not including clouds); carbon dioxide (CO2), which causes 9–26%; methane (CH4), which causes 4–9%; and ozone, which causes 3–7%.[25][26] Molecule for molecule, methane is a more effective greenhouse gas than carbon dioxide, but its concentration is much smaller so that its total radiative forcing is only about a fourth of that from carbon dioxide. Some other naturally occurring gases contribute very small fractions of the greenhouse effect; one of these, nitrous oxide (N2O), is increasing in concentration owing to human activity such as agriculture. The atmospheric concentrations of CO2 and CH4 have increased by 31% and 149% respectively since the beginning of the industrial revolution in the mid-1700s. These levels are considerably higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from ice cores. From less direct geological evidence it is believed that CO2 values this high were last attained 20 million years ago.[27] Fossil fuel burning has produced about three-quarters of the increase in CO2 from human activity over the past 20 years. Most of the rest is due to land-use change, in particular deforestation.[28]
Recent increases in atmospheric carbon dioxide (CO2). The monthly CO2 measurements display small seasonal oscillations in an overall yearly uptrend; each year's maximum is reached during the Northern Hemisphere's late spring, and declines during the Northern Hemisphere growing season as plants remove some CO2 from the atmosphere.

The present atmospheric concentration of CO2 is about 385 parts per million (ppm) by volume.[29] Future CO2 levels are expected to rise due to ongoing burning of fossil fuels and land-use change. The rate of rise will depend on uncertain economic, sociological, technological, and natural developments, but may be ultimately limited by the availability of fossil fuels. The IPCC Special Report on Emissions Scenarios gives a wide range of future CO2 scenarios, ranging from 541 to 970 ppm by the year 2100.[30] Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal, tar sands or methane clathrates are extensively used.[31]
Although it is difficult to connect specific weather events to global warming, an increase in global temperatures may in turn cause broader changes, including glacial retreat, Arctic shrinkage, and worldwide sea level rise. Changes in the amount and pattern of precipitation may result in flooding and drought. There may also be changes in the frequency and intensity of extreme weather events. Other effects may include changes in agricultural yields, addition of new trade routes,[69] reduced summer streamflows, species extinctions, and increases in the range of disease vectors.
Some effects on both the natural environment and human life are, at least in part, already being attributed to global warming. A 2001 report by the IPCC suggests that glacier retreat, ice shelf disruption such as that of the Larsen Ice Shelf, sea level rise, changes in rainfall patterns, and increased intensity and frequency of extreme weather events, are being attributed in part to global warming.[70] While changes are expected for overall patterns, intensity, and frequencies, it is difficult to attribute specific events to global warming. Other expected effects include water scarcity in some regions and increased precipitation in others, changes in mountain snowpack, and adverse health effects from warmer temperatures.
Increasing deaths, displacements, and economic losses projected due to extreme weather attributed to global warming may be exacerbated by growing population densities in affected areas, although temperate regions are projected to experience some benefits, such as fewer deaths due to cold exposure.[72] A summary of probable effects and recent understanding can be found in the report made for the IPCC Third Assessment Report by Working Group II.[70] The newer IPCC Fourth Assessment Report summary reports that there is observational evidence for an increase in intense tropical cyclone activity in the North Atlantic Ocean since about 1970, in correlation with the increase in sea surface temperature, but that the detection of long-term trends is complicated by the quality of records prior to routine satellite observations. The summary also states that there is no clear trend in the annual worldwide number of tropical cyclones.
Additional anticipated effects include sea level rise of 110 to 770 millimeters (0.36 to 2.5 ft) between 1990 and 2100,[73] repercussions to agriculture, possible slowing of the thermohaline circulation, reductions in the ozone layer, increased intensity of hurricanes and extreme weather events, lowering of ocean pH, and the spread of diseases such as malaria and dengue fever. One study predicts 18% to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections.[74] However, few mechanistic studies have documented extinctions due to recent climate change[75] and one study suggests that projected rates of extinction are uncertain.[76]

ECONOMIC
The projected temperature increase for a range of stabilization scenarios (the colored bands). The black line in middle of the shaded area indicates 'best estimates'; the red and the blue lines the likely limits. From the work of IPCC AR4.
Some economists have tried to estimate the aggregate net economic costs of damages from climate change across the globe. Such estimates have so far failed to reach conclusive findings; in a survey of 100 estimates, the values ran from US$-10 per tonne of carbon (tC) (US$-3 per tonne of carbon dioxide) up to US$350/tC (US$95 per tonne of carbon dioxide), with a mean of US$43 per tonne of carbon (US$12 per tonne of carbon dioxide).[72] One widely publicized report on potential economic impact is the Stern Review; it suggests that extreme weather might reduce global gross domestic product by up to 1%, and that in a worst-case scenario global per capita consumption could fall 20%.[77] The report's methodology, advocacy and conclusions have been criticized by many economists, primarily around the Review's assumptions of discounting and its choices of scenarios,[78] while others have supported the general attempt to quantify economic risk, even if not the specific numbers.
In a summary of economic cost associated with climate change, the United Nations Environment Programme emphasizes the risks to insurers, reinsurers, and banks of increasingly traumatic and costly weather events. Other economic sectors likely to face difficulties related to climate change include agriculture and transport. Developing countries, rather than the developed world, are at greatest economic risk.[81]

SECURITY:
In November 2007, the Center for Strategic and International Studies and the Center for a New American Security published a report highlighting the national security effects of climate change.[82] These security effects include increased competition for resources between countries, mass migration from the worst affected areas, challenges to the cohesion of major states threatened by the rise in sea levels, and, as a consequence of these factors, an increased risk of armed conflict, including even nuclear conflicts.

CLIMATE MODELS:
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.
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).
Global climate model
Scientists have studied global warming with computer models of the climate. These models are based on physical principles of fluid dynamics, radiative transfer, and other processes, with simplifications being necessary because of limitations in computer power and the complexity of the climate system. All modern climate models include an atmospheric model that is coupled to an ocean model and models for ice cover on land and sea. Some models also include treatments of chemical and biological processes.[62]These models predict that the effect of adding greenhouse gases is to produce a warmer climate.[63] However, even when the same assumptions of future greenhouse gas levels are used, there still remains a considerable range of climate sensitivity.
Including uncertainties in future greenhouse gas concentrations and climate modeling, 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.[1] Models have also been 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.
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.[64] These models do not unambiguously attribute the warming that occurred from approximately 1910 to 1945 to either natural variation or human effects; however, they suggest that the warming since 1975 is dominated by man-made greenhouse gas emissions.
Global climate model projections of future climate are forced by imposed greenhouse gas emission scenarios, most often from the IPCC Special Report on Emissions Scenarios (SRES). Less commonly, models may also include a simulation of the carbon cycle; this generally shows a positive feedback, though this response is uncertain (under the A2 SRES scenario, responses vary between an extra 20 and 200 ppm of CO2). Some observational studies also show a positive feedback.
The representation of clouds is one of the main sources of uncertainty in present-generation models, though progress is being made on this problem.[68]
Put this four-point plan into action and we can drastically cut global warming pollution.
We have solutions in hand right now to drastically cut global warming pollution. Act now -- put clean, innovative energy technologies to use, and enact policies to encourage their rapid, widespread adoption -- and we can stop global warming in its tracks. Instead of nearly doubling U.S. global warming pollution by 2050, we can cut it by more than half using today's technology. And with the proper incentives in place, even more innovative solutions will emerge along the way, leading to even bigger reductions.
This four-point plan is how we get started.
"In my view, climate change is the most severe problem that we are facing today -- more serious even than the threat of terrorism."
With this warning to an international science meeting in February 2004, David A. King, Chief Scientific Advisor to the British Government, brought the issue of global warming into sharp focus.
The World View of Global Warming project is documenting this change through science photography from the Arctic to Antarctica, from glaciers to the oceans, across all climate zones. Rapid climate change and its effects is fast becoming one of the prime events of the 21st century. It is real and it is accelerating across the globe. As the effects of this change combine with overpopulation and weather crises, climate disruptions will affect more people than does war.
The 2005 average global temperature equaled (within several hundredths of a degree) the record warm year of 1998, according to meteorologists. 2002-4 were nearly as warm, and the 11 warmest years on record have all occurred since 1990. In response, our planet has been changing with warming winds and rising seas. At the poles and in mountains, ice is under fire and glaciers are receding. Down into the temperate zone, change is rearranging the boundaries of life. The plants and animals with whom we share the planet are adapting and moving -- some even going extinct -- because they have no choice.
We six billion humans are being affected, too. Coastal towns are suffering from rising sea level, storms are getting stronger and 35,000 people died in European heat waves in 2003. However, we have choices to make to help correct and ameliorate global warming. This is a story of frightening scale and great urgency that is just beginning to be told. Please go to Actions to see what you can do now.
I began photographing climate change in 1999, about when scientists started to realize how great a change in temperatures is taking place in our time. Past earth temperatures left their mark in tree rings, glaciers and ancient lake and ocean sediments, and the record shows slowly decreasing temperatures over the last 2000 years. In that time there have been warm and cool periods, but nothing like the rise in temperatures in the past 150 years -- and no increase even close to the past 30. This research has created what has become the single most powerful icon of climate change, the so-called "hockey-stick" graph of temperatures. In 2005-6 it was subjected to intense re-analysis. Evidence of previous cool and warm periods has increased, but the rapid and sustained heat gain especially since the 1970s remains unparalleled in recent earth history.
In general global temperatures have risen since the 19th century industrial revolution. There is little scientific question the reason is a steep increase in atmospheric carbon dioxide -- CO2 -- from human use of fossil fuels. Methane, ozone, other gases and dusts have also increased greatly. The mechanism of our atmosphere is that gases like CO2 and methane trap some of the sun's radiation and hold it in the lower atmosphere, heating it. The natural greenhouse effect made the earth warm enough for life, but the effect is much higher now. Ice core records show that whenever CO2 has increased in the earth's past, so has temperature. The recent increase in atmospheric CO2 is 200 times as great as any previous change seen in the ice cores. The current level is 380 parts per million, the highest in more than 650,000 years. It shows no signs of decreasing.
This increase caused earth's average atmospheric temperature to go up about 1. degree F in the 20th century. Now, according to NOAA, the global warming rate in the last 25 years has risen to 3.6 degrees F per century. This tends to confirm the predictions of temperature increases made by international panels of climate scientists (IPCC). The ocean has actually absorbed most of the added CO2 and heat -- becoming warmer and very slightly more acidic. These increases, seemingly small, have a giant effect on weather, climate zones, plants and animals, sea life, glaciers and river flow -- and thus human life. My project and this Web site seek to document these changes. For more on past climate and today's weather, see especially the Paleoclimate and Weather sections.
FEEDBACK CYCLES IN GLOBAL WARMING:
One of the causes of global warming, or more generally, global climate change is increased atmospheric CO2 that comes from anthropogenic sources. Human activity is increasing the release of CO2 into the atmosphere by burning fossil fuels, burning forests, deforestation and destruction of the soil, along with other activities. This pulse of CO2 into the atmosphere is a perturbation and the earth system will respond with some changes. Our focus is to attempt to identify important responses and determine whether these responses will counter the increase in CO2 or temperature, or whether the response will exacerbate the change.
In a systems view of this system, we are looking for feedback cycles that are either positive or negative (Figure 1). A negative feedback cycle will resist change with compensatory flows in other parts of the system. Conversely, a positive feedback will accelerate the rate of change.


Figure1. Several possible feedback cycles for global warming. The
details are discussed in the text below.
• There is a negative feedback cycle involving CO2, temperature and algae.
 increased CO2 causes surface temperature to rise
 which leads to increased algae growth rates in the ocean,
 which depletes atmospheric CO2
 thus countering the rise in atmospheric CO2.
• There is a positive feedback cycle involving air temperature, CO2 and soil organisms.
 increased CO2 causes surface temperature to rise
 increased temperature causes soil organisms to respire faster
 faster respiration converts more soil organics to CO2
 thus accelerating the cycle of CO2 input.
• There is another positive feedback involving surface albedo of glaciers and temperature.
 increased temperature causes glaciers to melt
 the loss of reflective surface of the glacier leads to more absorption of sunlight
 more absorption leads to higher temperatures
 thus accelerating the melting and temperature rise
It is crucial that we understand these cycles and the potential interaction between these cycles.The negative feedback cycles will lead to controlling or minimizing temperature gain, whereas positive feedback processes will contribute to acceleration of the problem. If we are very lucky, there may be very strong negative feedback controls that will buffer human impact. If we are less lucky, a slight anthropogenic change may trigger a set or processes that will cause a shift in the processes that control surface temperature. In terms of resilience; if the overall global system is very resilient, human perturbation may be quickly fixed, on the other hand, once we cross a threshold (exceed the resilience) there may be a dramatic and essentially irreversible shift in the fundamental processes of the system.

Effects on agriculture
Main article: Climate change and agriculture
For some time it was hoped that a positive effect of global warming would be increased agricultural yields, because of the role of carbon dioxide in photosynthesis, especially in preventing photorespiration, which is responsible for significant destruction of several crops. In Iceland, rising temperatures have made possible the widespread sowing of barley, which was untenable twenty years ago. Some of the warming is due to a local (possibly temporary) effect via ocean currents from the Caribbean, which has also affected fish stocks.[102]
While local benefits may be felt in some regions (such as Siberia), recent evidence is that global yields will be negatively affected. "Rising atmospheric temperatures, longer droughts and side-effects of both, such as higher levels of ground-level ozone gas, are likely to bring about a substantial reduction in crop yields in the coming decades, large-scale experiments have shown" [103].
Moreover, the region likely to be worst affected is Africa, both because its geography makes it particularly vulnerable, and because seventy per cent of the population rely on rain-fed agriculture for their livelihoods. Tanzania's official report on climate change suggests that the areas that usually get two rainfalls in the year will probably get more, and those that get only one rainy season will get far less. The net result is expected to be that 33% less maize—the country's staple crop—will be grown.[104]


Climate change may be one of the causes of t

he Darfur conflict. The combination of decades of drought, desertification and overpopulation are among the causes of the conflict, because the Arab Baggara nomads searching for water have to take their livestock further south, to land mainly occupied by farming peoples.[105]
"The scale of historical climate change, as recorded in Northern Darfur, is almost unprecedented: the reduction in rainfall has turned millions of hectares of already marginal semi-desert grazing land into desert. The impact of climate change is considered to be directly related to the conflict in the region, as desertification has added significantly to the stress on the livelihoods of pastoralist societies, forcing them to move south to find pasture," the UNEP report states.[106]
In 2007, higher incentives for farmers to grow non-food biofuel crops[107] combined with other factors (such as rising transportation costs, climate change, growing consumer demand in China and India, and population growth)[108] to cause food shortages in Asia, the Middle East, Africa, and Mexico, as well as rising food prices around the globe.[109][110] As of December 2007, 37 countries faced food crises, and 20 had imposed some sort of food-price controls. Some of these shortages resulted in food riots and even deadly stampedes.[111][112][113]
See also: Food security, Food vs fuel, and 2007–2008 world food price crisis

Flood defense
For historical reasons to do with trade, many of the world's largest and most prosperous cities are on the coast, and the cost of building better coastal defenses (due to the rising sea level) is likely to be considerable. Some countries will be more affected than others—low-lying countries such as Bangladesh and the Netherlands would be worst hit by any sea level rise, in terms of floods or the cost of preventing them. Still, in 180 of 192 littoral countries worldwide, coastal protection will cost less than 0.1% of the country's gross domestic product.[114]
In developing countries, the poorest often live on flood plains, because it is the only available space, or fertile agricultural land. These settlements often lack infrastructure such as dykes and early warning systems. Poorer communities also tend to lack the insurance, savings or access to credit needed to recover from disasters.[115]

Migration
Some Pacific Ocean island nations, such as Tuvalu, are concerned about the possibility of an eventual evacuation, as flood defense may become economically unviable for them. Tuvalu already has an ad hoc agreement with New Zealand to allow phased relocation.[116]
In the 1990s a variety of estimates placed the number of environmental refugees at around 25 million. (Environmental refugees are not included in the official definition of refugees, which only includes migrants fleeing persecution.) The Intergovernmental Panel on Climate Change (IPCC), which advises the world’s governments under the auspices of the UN, estimated that 150 million environmental refugees will exist in the year 2050, due mainly to the effects of coastal flooding, shoreline erosion and agricultural disruption (150 million means 1.5% of 2050’s predicted 10 billion world population).[117][118]

Northwest Passage

Arctic ice thicknesses changes from 1950s to 2050s simulated in one of GFDL's R30 atmosphere-ocean general circulation model experiments
Melting Arctic ice may open the Northwest Passage in summer, which would cut 5,000 nautical miles (9,000 km) from shipping routes between Europe and Asia. This would be of particular benefit for supertankers which are too big to fit through the Panama Canal and currently have to go around the tip of South America. According to the Canadian Ice Service, the amount of ice in Canada's eastern Arctic Archipelago decreased by 15% between 1969 and 2004.[119]

In September 2007, the Arctic Ice Cap retreated far enough for the Northwest Passage to become navigable to shipping for the first time in recorded history.[120]
In August, 2008, melting sea ice simultaneously opened up the Northwest Passage and the Northern Sea Route, making it possible to sail around the Arctic ice cap. Scientists estimate that this hasn't happened in 125,000 years.[121] The Northwest Passage opened August 25, 2008, and the remaining tongue of ice blocking the Northern Sea Route dissolved a few days later. Because of arctic shrinkage, the Beluga group of Bremen, Germany, announced plans to send the first ship through the Northern Sea Route in 2009.[122]

Development
The combined effects of global warming may have particularly harsh effects on people and countries without the resources to mitigate those effects. This may slow economic development and poverty reduction, and make it harder to achieve the Millennium Development Goals.[123]
In October 2004 the Working Group on Climate Change and Development, a coalition of development and environment NGOs, issued a report Up in Smoke on the effects of climate change on development. This report, and the July 2005 report Africa - Up in Smoke? predicted increased hunger and disease due to decreased rainfall and severe weather events, particularly in Africa. These are likely to have severe impacts on development for those affected.

Conclusion
Conclusion of global warming
The bottom line it is coming (if not already here) and we have to figure out what we can do. Waters rising will be a disaster, food will be affected and we gotta plan for catastrophies like katrina. This is gonna hit everyone, not just the poor or the democrats or the catholics--we're all in a heap of trouble and the sooner we accept this FACT. We should put serious effort to overcome the problems due to it. We must try our best to solve the problem and strive as much as possible to reinstate our earth for sake of future generation.