ENVIRONMENT CHANGES

Introduction:

The climate has always been changing.on every timescaale,scince the earth was first formed is surface conditions have fluctuated. Past change are etched on the land scape, have influnced the evoluation of all life forms, and are a subtext of our economice and social history. Current changes are a central part of the debate about the conceqences of the human activities on the global environment, while the future course of the climet could exert powerful constraints on the economic development, specially in developing countrys. In our project we have to define the meaning of climate change and effect of the golbal warming on Bangladesh and all over the world.

Climate:

Climete is what would be expected to occur at any given time of the year based on statistics built up over many years. Defination of the Climate is the average and variations of weather over long periods of time. Climate zones can be defined using parameters such as temperature and rainfall. Paleoclimatology focuses on ancient climate information derived from sediment found in lake beds, ice cores, as well as various fauna and flora including tree rings and coral.. Climate in a narrow sense is usually defined as the “average weather”, or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period is 30 years, as defined by the World Meteorological Organization. These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system.

Climate change:

Climate changes refer to the difference in the Earth’s global climate or in regional climates over time. It describes changes in the variability or average state of the atmosphere over time scales ranging from decades to millions of years. These changes can be caused by processes internal to the Earth, external forces (e.g. variations in sunlight intensity) or, more recently, human activities. Earth has undergone periodic climate shifts in the past, including four major ice ages. The accumulation of snow and ice during a glacial period increases the surface albedo, reflecting more of the Sun’s energy into space and maintaining a lower atmospheric temperature. Increases in greenhouse gases, such as by volcanic activity, can increase the global temperature and produce an interglacial. Suggested causes of ice age periods include the positions of the continents, variations in the Earth’s orbit, changes in the solar output, and vulcanism.

Causes of climate change:

The general state of the Earth’s climate is largely affected by how much heat is stored in the atmosphere. Processes which affect this storage of heat can cause the climate of the Earth to change. It is not just man-made pollution of the atmosphere which can cause climate change. Changes in the amount of greenhouse gases in the air have occurred Illustrates the basic components that influence the state of the Earth’s climatic system. Changes in the state of this system can occur externally (from extraterrestrial systems) or internally (from ocean, atmosphere and land systems) through any one of the described components. For example, an external change may involve a variation in the Sun’s output which would externally vary the amount of solar radiation received by the Earth’s atmosphere and surface. Internal variations in the Earth’s climatic system may be caused by changes in the concentrations of atmospheric gases, mountain building, volcanic activity, and changes in surface or atmospheric aldedo.

Factors that influence the Earth’s climate

Naturally during the history of the Earth, leading to climate changes. Changes in the way ocean water circulates around the world can also influence climate, because the oceans store even more heat than the atmosphere. Changes in the amount of heat from the Sun will affect the Earth’s climate. Large volcanic eruptions can cause the Earth to cool over a couple of years, because huge amounts of pollution injected in to the air block out a lot more sunlight. This type of climate change can also occur when a large comet or meteorite strikes the Earth. Luckily, this only happens every few million years. Other processes can change the Earth’s climate, but only very, very slowly, over millions of years. When continents move around the world, and when mountains ranges are built, the changing patterns of landmasses affects the way the heat in the atmosphere and in the oceans is stored. Continental drift however, takes millions of years, and so therefore does any climate change caused by it

Attribution of 20th century climate change:

One global climate model,s reconstruction of temperature change during the 20th century as the result of five studied forcing factors and the amount of temperature change attributed to each.

Over the past 150 years human activities have released increasing quantities of greenhouse gases into the atmosphere. This has very likely led to increases in mean global temperature, or global warming. Other human effects are relevant for example, sulphate aerosols are believed to lead to cooling and natural factors also contribute. According to the historical temperature record of the last century, the Earth’s near-surface air temperature has risen around 0.74 ± 0.18 ° (1.3 ± 0.32 °).

1. Anthropogenic warming of the climate system is widespread and can be detected in temperature observations taken at the surface, in the free atmosphere and in the oceans. Evidence of the effect of external influences, both anthropogenic and natural, on the climate system has continued to accumulate since the TAR.Estimates of internal variability from climate models, and reconstructions of past temperatures, indicate that the warming is unlikely to be entirely natural.

2. Climate models forced by natural factors and increased greenhouse gases and aerosols reproduce the observed global temperature changes; those forced by natural factors alone do not.

3. “Fingerprint” methods indicate that the pattern of change is closer to that expected from greenhouse gas-forced change than from natural change.

4. The plateau in warming from the 1940s to 1960s can be attributed largely to sulphate aerosol cooling.

Effect of Climate change on globally:

As a result of the climate change is very unsafe for the entire world. It can arise many sort of Natural and health problem. All the problems are explain as following.

Global warming:

In recent usage, especially in the context of environmental change” often refers only to changes in modern climate, including policy, the term “climate the rise in average surface temperature known as global warming.

Increase in the global average surface temperature resulting from enhancement of the greenhouse effect, primarily by air pollution. In 2007 the UN Intergovernmental Panel on

Climate Change forecasted that by 2100 global average surface temperatures would increase 3.2 – 7.2 °F (1.8 – 4.0 °C), depending on a range of scenarios for greenhouse gas emissions, and stated that it was now 90 percent certain that most of the warming

The net impact of global warming so far has been modest, but near-future effects are likely to become significantly negative, with large-scale extreme impacts possible by the end of the century. Other scientists maintain that such predictions are overstated. The 1992 Earth Summit and the 1997 Kyoto Protocol to the United Nations Framework Convention on Climate Change attempted to address the issue of global warming, but in both cases the efforts were hindered by conflicting

National economic agendas and disputes between developed and developing nations over the cost and consequences of reducing emissions of greenhouse gases.

The greenhouse effect:

Mechanisms 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 warms a planet’s atmosphere and surface.

Greenhouse gases create a natural greenhouse effect, without which mean temperatures on Earth would be an estimated 30 °C (54 °F) lower so that Earth would be uninhabitable. Thus scientists do not “believe in” or “oppose” the greenhouse effect as such; rather, the debate concerns the net effect of the addition of greenhouse gases, while allowing for associated positive and negative feedback.

On Earth, the major natural greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect (not including clouds); carbon dioxide , which causes 9–26%; methane, which causes 4–9%; and ozone, which causes 3–7%. 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 above pre-industrial levels since 1750. 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. About three-quarters of the anthropogenic [man-made] emissions of CO₂ to the atmosphere during the past 20 years are due to fossil fuel burning. The rest of the anthropogenic emissions are predominantly due to land-use change, especially deforestation.

The present atmospheric concentration of CO₂ is about 383 parts per million (ppm) by volume. 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, 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. Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal, tar sands or methane clathrates are extensively used.

Positive feedback effects such as the expected release of CH₄ from the melting of permafrost peat bogs in Siberia (possibly up to 70,000 million tonnes) may lead to significant additional sources of greenhouse gas emissions not included in climate models cited by the IPCC.

Solar variation:

Variations in solar output, possibly amplified by cloud feedbacks, may have contributed to recent warming. A difference between this mechanism and greenhouse warming is that an increase in solar activity should produce a warming of the stratosphere while greenhouse warming should produce a cooling of the stratosphere. Reduction of stratospheric ozone also has a cooling influence but substantial ozone depletion did not occur until the late 1970s. Cooling in the lower stratosphere has been observed since at least 1960. Thus, solar activity alone is not the main contributor to recent warming.

Phenomena such as solar variation combined with volcanoes have probably had a warming effect from pre-industrial times to 1950, but a cooling effect since 1950. However, some research has suggested that the Sun’s contribution may have been underestimated. Two researchers at Duke University have estimated that the Sun may have contributed about 40–50% of the global surface temperature warming over the period 1900–2000, and about 25–35% between 1980 and 2000. Stott and coauthors suggest that climate models overestimate the relative effect of greenhouse gases compared to solar forcing; they also suggest that the cooling effects of volcanic dust and sulfate aerosols have been underestimated. Nevertheless, they conclude that even with enhanced climate sensitivity to solar forcing, most of the warming during the latest decades is attributable to the increases in greenhouse gases.

How effect on globally:

As a result of the climate change is very unsafe for the entire world. It can arise many sort of Natural and health problem. All the problems are explained as following.

Natural Disasters:

Climate change will increase the risk of both floods and drought. Ninety percent of disaster victims worldwide live in developing countries, where poverty and population pressures force growing numbers of people to live in harm’s way—on flood plains and on unstable hillsides. Unsafe buildings compound the risks. The vulnerability of those living in risk-prone areas is perhaps the single most important cause of disaster casualties and damage.

Impacts on Health:

To assess the potential impacts of climate change on health, it is necessary to consider both the sensitivity and vulnerability of populations for specific health outcomes to changes in temperature, rainfall, humidity, storminess, and so on. Vulnerability is a function both of the changes to exposure in climate and of the ability to adapt to that exposure.

Science classically operates empirically, via observation, interpretation, and replication. However, having initiated a global experiment, it would not be advisable to wait decades for sufficient empirical evidence to describe the health consequences. Risk assessment must therefore be carried out in relation to future environmental scenarios. The traditional “top-down” approach is to answer the question, “If climate changes like scenario X, then what will be the effect on specific health outcomes?” In contrast, “bottom-up” approaches begin with the question, “How much climate change can be tolerated?”

It is important to distinguish between “climate and health” relationships and “weather and health” relationships. Climate variability occurs on many time scales. Weather events occur at daily time scale and are associated with many health impacts (e.g., heat waves and floods). Climate variability at other time scales also affects health. In particular, the El Niño Southern Oscillation has been shown to influence internal variability in malaria, dengue, and other mosquito-borne diseases. Climate change is the long-term change in the average weather conditions for a particular location. Climate change will become apparent as a change in annual, seasonal, or monthly means. Thus, incremental climate change will be superimposed upon the natural variability of climate in time and space.

Vulnerability is to build the infrastructure to remove solid waste and waste water and supply potable water. No sanitation technology is “safe” when covered by flood waters, as fecal matter mixes with flood waters and is spread wherever the flood waters go.

How effect on Bangladesh:

Climate: baseline, scenarios, and key vulnerabilities:

This section briefly reviews projections of temperature and precipitation change for Bangladesh from climate models, and then addresses the major risks from climate change that Bangladesh may face. The sect oral risk is presented in order of importance. This order is based on subjective judgments about the significance of climate change impacts (which is a function of severity and importance of the affected resource), timing of impacts (whether the impacts are likely to be significant or noticeable in first half of this century or not until the latter half), and certainty of impact (any uncertainties about the relationship with climate change or the nature of the climate change itself.

Climate change and sea level rise projections:

Sea level rise:

Another critical variable that determines the vulnerability of Bangladesh to climate change impacts is the magnitude of sea level rise. There is no specific regional scenario for net sea level rise, in part because the Ganges-Brahmaputra delta is still active and the morphology highly dynamic. Literature suggests that the coastal lands are receiving additional sediments due to tidal influence, while there are parts where land is subsiding due to tectonic activities (Huq et al. 1996). Since the landform is constituted by sediment decomposition, compaction of sediment may also play a role in defining net change in sea level along the coastal zone. A review of the literature and of expert opinion suggests that sediment loading may cancel out the effect of compaction and subsidence, so that net sea level rise may be assumed. The Bangladesh country study put the range at 30-100 cm by 2100, while the IPCC Third Assessment gives a global average range with slightly lower values of 9 to 88 cm. In any event the increases in mean sea level need to be viewed in conjunction with the discussion on cyclones in the preceding section. Higher mean sea levels are likely to compound the enhanced storm surges expected to result from cyclones with higher intensity. Even in non cyclone situations, higher mean sea levels are going to increase problems of coastal inundation and Stalinization in the low lying deltaic coast.

The reduction in freshwater flows would only deteriorate with time and the lowest water levels would be expected in March. As a response to reduced flow regime the salinity front would penetrate inland both inside the forest areas and in the entire south-western areas of the country. Similar ingress of salinity is also expected on the Indian side of the Sundarbans. The effect of sea level rise on salinity ingress is modeled here using the salinity model of the Institute of Water Management (IWM), Bangladesh. Considering about 23 cm of SLR, isohaline lines penetrate inland, as shown in Figure 9 Significant penetration has been indicated for the threshold salinity of 1 pot or higher for the rivers supplying freshwater in the western and central parts of the Sundarbans: Betna, upper Bhairab and Kobadak.

Salinity ingress in the Sundarbans under 23 cm sea level rise:

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If an increased sea level rise of 44 cm is considered a relatively higher penetration is expected to occur along the western parts of the GDA for the isohaline limits of 1, 5 and 10 ppt. It must however be mentioned that the model offers results of low confidence due to its limitation of using a fixed salinity boundary along the downstream of rivers. The modeling results are indicative, and actual salinity ingress would be compounded but when model results are superimposed on the possibility of reduction of surface flows during the peak low flow period, one may have an understanding of the extent of salinity ingress along the rivers in the Sundarbans. As a consequence of salinity penetration in the Sundarbans, majority of the marshaling areas will be transformed into polyamine areas, while oligohaline areas would be reduced to only a small pocket along the lower-Bales war river in the eastern part of the forest. Such a finding closely supports earlier studies.

Water resources:

Water related impacts of climate change will likely be the most critical for Bangladesh – largely related to coastal and reverie flooding, but also enhanced possibility of winter (dry season) drought in certain areas. The effects of increased flooding resulting from climate change will be the greatest problem faced by Bangladesh. Both coastal flooding (from sea and river water), and inland flooding (river/rain water) are expected to increase.

Flooding in Bangladesh is a regular feature and has numerous adverse effects, including loss of

Life through drowning increased prevalence of disease, and destruction of property. This is because much of the Bangladesh is located on a floodplain of three major rivers and their numerous tributaries.

One-fifth of the country is flooded every year, and in extreme years, two-thirds of the country can be inundated (Mirza, 2002). This vulnerability to flooding is exacerbated by the fact that Bangladesh is also allow-lying deltaic nation exposed to storm surges from the Bay of Bengal.

Physiographic of Bangladesh showing major floodplains:

There has been a trend in recent decades of much higher inter-annual variation in area flooded. Since the late 1970s flooding events have tended to cover significantly lower or significantly higher areas than what was observed in prior decades. This trend in extremes cannot be simply attributed to climate change. Rather several other factors are at play. First, better flood monitoring and control measures have probably contributed to significant reduction in area coverage of moderate flooding events, which now cover much lower area.

Human health:

The combination of higher temperatures and potential increases in summer precipitation could create the conditions for greater intensity or spread of many infectious diseases. However, risk in the human health sector is low relative to climate change induced risks in other sectors (such as water resources) mainly because of the higher uncertainty about many of the health outcomes. Increased risk to human health from increased flooding and cyclones seems most likely. Changes in infectious disease are less certain. The causes of outbreaks of infectious disease are quite complex and often do not have a simple relationship with increasing temperature or change in precipitation. It is not clear if the magnitude of the change in health risks resulting from climate change will be significant compared to current risks. It is also not clear if increased health risk will be apparent in the next few decades. On the whole climate change is expected to present increased risks to human health in Bangladesh, especially in light of the poor state of the country’s public health infrastructure. Life expectancy is only 61 years, and 61% of children are

Malnourished (World Bank, 2002). Perhaps more illustrative of this point, though, is the US$12 per person per year that the Bangladeshi government expends on health, well below the US$21 spent in low income countries in general (World Bank, 2002).

Agriculture:

With over 35% of Bangladeshis suffering from malnourishment (Lal et al., 2001), the threat of Increased hunger from reduction in agricultural production would suggest the inclusion of agriculture as one of the major vulnerabilities facing the country. Yet the IPCC (Lal et al., 2001) and other studies (e.g., Karim et al., 1996) show crop yields potentially increasing at a few degrees Celsius increase in temperature (see Tables 2.3 and 2.4). Beyond that, particularly as the CO2 fertilization saturates, yields could decrease. For example, Karim et al. (1996) estimated that rice yields would increase for about a 1.5°C increase combined with higher CO2 levels.

Resource/ranking	Certainty of Impact	Timing of Impact	Severity of Impact	Importance Of resource
Water resources (Flooding)	Medium high	High	High	High
Coastal resources	High	Low	High	High
Human health	Low medium	Medium	Medium high	High
Agriculture	Medium	Low-medium	Low medium	High

Priority ranking of climate change risks for Bangladesh