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Climate Change - The Effects




Sea levels

Changes in the 20th century : Sea levels rose in th 20th century by between 10 - 20cm. Much of this can be related to the increase in global mean temperatures.

Rising sea levels are largely a consequence of the thermal expansion of the ocean, melting of low latitude glaciers e.g. in the Alps and Rockies and many other factors, each of which are reviewed every few years by the Intergovernmental Panel on Climate Change (IPCC).


The Arctic : The Arctic region is warming at two to three times the rate for the rest of the world.

Precipitation in the Arctic has increased by 8% on average over the past century, accompanied by rising river flows and sea level rise. Snow cover has declined by 10% over the past 30 years, reducing the earth’s reflective capacity and increasing heat absorption through greater exposure of darker ocean surfaces. Melting glaciers have reduced salinity impairing the Atlantic thermohaline circulation. Thawing permafrost will result in methane release.


Thermohaline circulation : There are three main processes that make the oceans circulate : tidal forces, wind stress and density differences. The density of sea water is controlled by its temperature (thermo) and its salinity (haline). Both of these are affected by mean global temperature and ocean currents can change. The Atlantic Gulf Stream, which keeps the weather in the UK mild, could be reversed, which would bring much colder weather to Western Europe. 


The future : Global mean sea levels are predicted to rise by 9 cm to 88 cm between the years 1990 and 2100. However, if all Greenland’s ice were to melt, then sea levels would rise by around 20 feet or 6.5 metres. It is currently losing about 200 cu km per annum, faster than any of the models have predicted.


Some consequences of rising sea levels : Many cities are built on the coast or rivers. Taking no other factors into account e.g. extreme rainfall, the rise in flooding consequent on rising sea levels would affect 50 – 200 million people across the world and have a dramatic effect on life and health.


Food production

Crops : In the short term, warming may improve agricultural yields in some cooler regions. However, significant reductions are highly likely to dominate in later decades of the present century, particularly for wheat, rice and maize. This would aggravate malnutrition that affects many regions. This is a growing problem even in the absence of climate change, due to growing populations, increasing economic disparities and the continuing shift of diet towards animal protein.


Fish : While some regions, such as the North Atlantic, might allow larger catches, a loss of marine productivity is expected in nearly all tropical waters, caused by warming and acidification. This affects poor countries in South-East Asia and the Pacific in particular. Many of these countries will also be affected disproportionately by the consequences of sea-level rise for coastal mega-cities. 



Heatwave-related health problems: Heatwaves are projected to become more frequent resulting in increased heat-related illness & deaths. The very old & young and chronically ill are most susceptible to heat related illness.


Winter-related illness & deaths: Cold-related illness, falls, road traffic accidents and deaths are likely to decline. This could be reversed, however, if there were to  be significant changes to the Thermohaline Circulation


River, Coastal Flooding & Flash Floods: The risk of major flooding disasters caused by severe winter gales, heavy rainfall and coastal erosion is likely to increase significantly accompanied with psychological consequences, disruption, injuries and deaths. River floods or storm surges, which can be forecast several days in advance, have fewer casualties compared to flash floods where there is no prior warning.


Infectious diseases: Cases of food poisoning and water borne disease  linked to warm weather are likely to increase.


Vector-borne diseases: Patterns of these diseases will change. 


Sunburn, skin cancer and cataract: These are all likely to increase. 


Extreme weather-related events : Natural disaters from, for example,  droughts and hurricanes lead to social disruption, injuries, deaths, disability, communicable disease outbreaks, interuption of immunisation programmes, migration and homelessness.


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