Global Warming | Assignment Help

Global warming is the phenomenon of increasing average air temperatures near the surface of Earth over the past one to two centuries. Since the mid-20th century, climate scientists have gathered detailed observations of various weather phenomena (such as temperature, precipitation, and storms) and of related influences on climate (such as ocean currents and the atmosphere’s chemical composition). These data indicate that Earth’s climate has changed over almost every conceivable timescale since the beginning of geologic time and that, since at least the beginning of the Industrial Revolution, the influence of human activities has been deeply woven into the very fabric of climate change. (US NRC, 2008)

A vigorous debate is in progress over the extent and seriousness of rising surface temperatures, the effects of past and future warming on human life, and the need for action to reduce future warming and deal with its consequences. The points to consider in this regard are the causes of rising near-surface air temperatures, the influencing factors, the process of climate research and forecasting, the possible ecological and social impacts of rising temperatures, and the public policy developments since the mid-20th century. (US NRC, 2008)

Future warming and related changes will vary from region to region around the globe. The effects of an increase in global temperature include a rise in sea levels and a change in the amount and pattern of precipitation, as well a probable expansion of subtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with the continuing retreat of glaciers, permafrost and sea ice. Other likely effects of the warming include a more frequent occurrence of extreme-weather events including heat waves, droughts and heavy rainfall, ocean acidification and species extinctions due to shifting temperature regimes. Effects significant to humans include the threat to food security from decreasing crop yields and the loss of habitat from inundation. (US NRC, 2008)

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Impacts of Global Warming

Vulnerability of human societies to climate change mainly lies in the effects of extreme-weather events rather than gradual climate change. Impacts of climate change so far include adverse effects on small islands, adverse effects on indigenous populations in high-latitude areas, and small but discernable effects on human health. Over the 21st century, climate change is likely to adversely affect hundreds of millions of people through increased coastal flooding, reductions in water supplies, increased malnutrition and increased health impacts. Most economic studies suggest losses of world gross domestic product (GDP) for this magnitude of warming. (Hansen & James, 2000)

Food security

Under present trends, by 2030, maize production in Southern Africa could decrease while rice, millet and maize in South Asia could decrease by up to 10%. By 2080, yields in developing countries could decrease by 10% to 25% on average while India could see a drop of 30% to 40%. By 2100, while the population of three billion is expected to double, rice and maize yields in the tropics are expected to decrease by 20–40% because of higher temperatures without accounting for the decrease in yields as a result of soil moisture and water supplies stressed by rising temperatures. (Hansen & James, 2000)

Future warming of around 3°C by 2100 could result in increased crop yields in mid and high latitude areas, but in low latitude areas, yields could decline, increasing the risk of malnutrition. A similar regional pattern of net benefits and costs could occur for economic (market-sector) effects. Warming above 3 °C could result in crop yields falling in temperate regions, leading to a reduction in global food production. (Hansen & James, 2000)

Drought

The effects of drought on health include deaths, malnutrition, infectious diseases and respiratory diseases. Countries within the “Meningitis Belt” in semi-arid sub-Saharan Africa experience the highest epidemic frequency of meningococcal meningitis in Africa, although other areas in the Rift Valley, the Great Lakes, and southern Africa are also affected. The spatial distribution, intensity, and seasonality of meningococcal (epidemic) meningitis appear to be strongly linked to climate and environmental factors, particularly drought. The cause of this link is not fully understood.

Ground-level ozone

Ground-level ozone is both naturally occurring and is the primary constituent of urban smog. Climate change would increase cardio-respiratory morbidity and mortality associated with ground-level ozone. Ozone in smog is formed through chemical reactions involving nitrogen oxides and other compounds. It occurs in the presence of bright sunshine and high temperatures. Exposure to elevated concentrations of ozone is associated with increased hospital admissions for pneumonia, chronic obstructive pulmonary disease, asthma, allergic rhinitis and other respiratory diseases, and with premature mortality. Background levels of ground-level ozone have risen since pre-industrial times because of increasing emissions of methane, carbon monoxide and nitrogen oxides. This trend is expected to continue into the mid-21st century. (Thuiller, et al, 2004)

Irreversible Impacts

Climate change may lead to irreversible impacts on physical, biological, and social systems. There are a number of examples of climate change impacts that may be irreversible, at least over the timescale of many human generations. These include the large-scale singularities described above – changes in carbon cycle feedbacks, the melting of the Greenland and West Antarctic ice sheets. In social systems, unique cultures may be lost due to climate change. For example, humans living on atoll islands face risks due to sea-level rise, sea-surface warming, and increased frequency and intensity of extreme weather events. In biological systems, the extinction of species would be an irreversible impact. (Araújo, et al, 2005)

Agriculture

Droughts have been occurring more frequently because of global warming and they are expected to become more frequent and intense in Africa, southern Europe, and the Middle East, most of the Americas, Australia, and Southeast Asia. Their impacts are aggravated because of increased water demand, population growth, urban expansion, and environmental protection efforts in many areas. Droughts result in crop failures and the loss of pasture grazing land for livestock. (Araújo, et al, 2005)

Health

Human beings are exposed to climate change through changing weather patterns – temperature, precipitation, sea-level rise and more frequent extreme events – and indirectly through changes in water, air and food quality and changes in ecosystems, agriculture, industry and settlements and the economy. World Health Organization – estimated the effect of climate change on human health. Not all of the effects of climate change were included in their estimates, for example, the effects of more frequent and extreme storms were excluded. Climate change was estimated to have been responsible for 3% of diarrhea, 3% of malaria, and 3.8% of dengue fever deaths worldwide. (Araújo, et al, 2005)

 Habitat Inundation

In small islands and mega deltas, inundation as a result of sea level rise is expected to threaten vital infrastructure and human settlements. This could lead to issues of statelessness for populations in countries such as the Maldives and homelessness in countries with low lying areas such as Bangladesh. (Araújo, et al, 2005)

Volcanoes

The retreat of glaciers and ice caps can cause increased volcanism. Reduction in ice cover reduces the confining pressure exerted on the volcano thus increasing the prospects and potentially causing the volcano to erupt. This reduction of pressure can also cause decompression melting of material in the mantle, resulting in the generation of more magma. While the original study addresses the first reason for increased volcanism (reduced confining pressure), scientists have more recently shown that these lavas have unusually high trace element concentrations. (Araújo, et al, 2005)

Sea level rise

The effects of current sea level rise could include increased crustal stress at the base of coastal volcanoes from a rise in the volcano’s water table. In addition, the wide-scale displacement of water from melting in places such as West Antarctica is likely to slightly alter the Earth’s rotational period and may shift its axial tilt on the scale of hundreds of meters, inducing further crustal stress changes. Current melting of ice is predicted to increase the size and frequency of volcanic eruptions. In particular, lateral collapse events at strato-volcanoes are likely to increase.

There are two main factors that have contributed to observed sea level rise. The first is thermal expansion: as ocean water warms, it expands. The second is from the contribution of land-based ice due to increased melting. The major store of water on land is found in glaciers and ice sheets. (Karl, et al, 2009)

Earthquakes

A numerical modeling study has demonstrated that seismicity increases during unloading, such as that due to the removal of ice.

Oceans

The role of the oceans in global warming is a complex one. The oceans serve as a sink for carbon dioxide, taking up much that would otherwise remain in the atmosphere, but increased levels of CO2 have led to ocean acidification. Furthermore, as the temperature of the oceans increases, they become less able to absorb excess CO2. The oceans have also acted as a sink in absorbing extra heat from the atmosphere. Global warming is projected to have a number of effects on the oceans. Ongoing effects include rising sea levels due to thermal expansion and melting of glaciers and ice sheets, and warming of the ocean surface, leading to increased temperature stratification. Other possible effects include large-scale changes in ocean circulation. (Karl, et al, 2009)

Acidification

About one-third of the carbon dioxide emitted by human activity has already been taken up by the oceans. As carbon dioxide dissolves in sea water, carbonic acid is formed, which has the effect of acidifying the ocean, measured as a change in pH. The effects of ocean acidification on the marine biosphere are catastrophic. Laboratory experiments suggest beneficial effects for a few species, with potentially highly detrimental effects for a substantial number of species. (US NRC, 2012)

Oxygen depletion

 The amount of oxygen dissolved in the oceans may decline, with adverse consequences for ocean life.

Floods and weather disasters

Floods are low-probability, high-impact events that can overwhelm physical infrastructure and human communities. The impacts of weather disasters are considerable and unequally distributed. For example, natural disasters have been shown to result in increased domestic violence against – and post-traumatic stress disorders in – women. In terms of deaths and populations affected, floods and tropical cyclones have the greatest impact in South Asia and Latin America. Vulnerability to weather disasters depends on the attributes of the person at risk, including where they live and their age, as well as other social and environmental factors. High-density populations in low-lying coastal regions experience a high health burden from weather disasters. (US NRC, 2012)

Case study of China

China is the largest producer of greenhouse gases and the largest emitter of carbon dioxide. China produces about 23 percent of the world’s carbon dioxide. It was not supposed to overtake the United States as the world’s leading producer of greenhouse gases until 2020 but a study released in 2010 determined that China was already the world’s No. 1 emitter of carbon dioxide then. It surpassed the United States in 2006 when it produced 7.5 percent more of these gasses than the United States compared to 2 percent less in 2005. In August 2008, it was surveyed that China’s carbon dioxide emissions in 2008 were 6.8 million tons—the most of any nation and 178 percent higher than the 1990 level. The United States and China together account for 40 percent of the world’s greenhouse gases -most of which is derived from coal. Per capita carbon emissions for each Chinese are 4.03 tons. (US NRC, 2012)