Impacts of global warming and climate change [Archives:2007/1098/Health]
Raymond Branke, MSc. and Magdi Masgidi, MSc.
Climate change is happening now and is transforming life on Earth faster than previously believed and its impact is worse than expected – this is the essence from the Fourth Assessment Report of the United Nations Intergovernmental Panel on Climate Change (IPCC), published earlier this year.
Environmental scientists and policy-makers from all over the world have been patiently waiting for this meta-study which summarises the present knowledge and research results on global warming and the inevitably connected climate change and gives the most precise description to date of what has caused temperatures to rise from 1800 right up to now. This report is certain to have a major political impact on the ongoing debate about climate change.
The 450 main authors and about 2,500 supporting experts worked over the past six years on the 2007 IPCC report, analysed calculations from hundreds of computer models and screened some 30,000 data sets from more than 70 international studies, documenting changes to water circulation and ice zones as well as to flora and fauna over a period of at least 20 years.
According to the IPCC, researchers observed distinct changes in the Earth's climate including atmospheric composition, global average temperatures, ocean conditions, and other climate changes. More than 85 percent of the data indicate “changes in a direction that would be expected as a reaction to warming.”
The report lists vast of evidence for a global climate change:
l Changes in the atmospheric composition: Carbon dioxide, methane, and nitrous oxide, which are all long-lasting greenhouse gases “have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values.”
– Eleven of the twelve years in the period 1995 – 2006 rank among the top 12 warmest years in the instrumental record since 1850. Warming in the last 100 years has caused about a 0.74 C increase in global average temperature. “Average Arctic temperatures increased at almost twice the global average rate in the past 100 years.”
– “Mountain glaciers and snow cover have declined on average in both hemispheres.” At the same time glacial lakes are increasing in both size and number, potentially leading to deadly floods.
– Permafrost in mountainous regions and at high latitudes is warming increasing the danger of land slides.
– There has been an increase in hurricane intensity in the North Atlantic since the 1970s, and that increase correlates with increases in sea surface temperature.
– As the temperature of rivers and lakes rises, their thermal stratification and water quality is changing.
– River currents, affected by melting glaciers and ice, are speeding up during spring.
– Springtime is starting earlier, causing plants to bloom earlier and changing the migrations of birds.
– Many plants and animals are expanding their habitats into mountainous regions and higher latitudes that are becoming milder.
For more than a century now, people have been relied on burning fossil fuels such as oil, coal and gas for their energy needs, emitting enormous amounts of carbon dioxide into the atmosphere, with the result that carbon dioxide concentrations are now the highest in 150,000 years. Other, even more potent greenhouse gasses are also significant, as is massive deforestation. These human influences “have had a recognizable effect on many physical and biological systems”, the IPCC report states. The observed changes in temperature and climate are considered “very unlikely” to be naturally occurring phenomena and with”very high confidence” that humans were responsible for most of the observed increase in globally averaged temperatures since the mid-20th century due to the observed increase in anthropogenic greenhouse gas concentrations.”
The UN experts not only describe the current situation. They also explore how landscapes and ecosystems will develop in the future as global climates change. In its summary, the report estimates that temperatures in the next 30 years will rise by 0.7 degrees Celsius. By 2100, temperatures could raise by as much as 6.4 degrees Celsius depending on the amount of greenhouse gases that will have been released into the atmosphere.
Rising temperatures will have consequences
The IPCC report lists in detail the potential consequences for most of the world and expect the most dramatic changes in terms of climate and landscape will take place in the northern-most latitudes due to the greatest relative warming. But other parts of the Earth will be also affected: Africa south of the Sahel zone will face extensive droughts. Small island states in the Pacific and the densely populated river deltas in Asia will suffer from flooding as sea levels rise. But southern oceans and the Atlantic are expected to be less effected. In most instances, global warming will cause negative effects for both humans and the environment across the globe. Some expected positive aspects – such as temporary better agricultural and forestry yields in northern Europe – will be more than outweighed by the expected negative effects due to rising temperatures and inevitably combined perils.
Changing landscapes and nature at risk
Rising temperatures and changing patterns of rain and snow are forcing plant communities to adjust by moving toward cooler and more humid areas and animals that depend on them will have to follow in order to survive. But the rapid nature of climate change is likely to exceed the ability of many species to migrate or adjust. If the warming trend continues at its current rate, IPCC experts predict that one-fourth of Earth's species is likely to fall victim to climate change by 2050 as they will have no chances to adopt.
Extensive changes in landscape and ecosystems due to rising temperatures are expected over wide areas, for instance in the tundra, thawing permafrost will allow shrubs and trees to take root and grasslands of North America will likely become forests. Tropical rainforests will be replaced by savannah in those regions where groundwater decreases. Some specialised species and communities from polar regions, alpine meadows or natural oases may be left without any remaining viable habitat. In the tropics, increased sea temperatures are causing more coral reefs to “bleach,” as the heat kills colourful algae that are necessary to coral health and survival.
As the Earth heats up, the report expects sea levels to rise due to thermal expansion of oceanic water, posing serious threat to lowlands throughout the world and speeding up the melting of the ice sheets that cover Greenland and Antarctica, that worsens the problem by adding even more water. In the past 100 years sea levels have risen at a rate of 1 to 2 mm/year; since 1993 satellite measurements indicates a rate of 3 to 4 mm/year. Current projections – that all exclude the contribution from ice sheet flow due to a lack of basis in published literature – suggest that sea levels could continue to rise between 180 to 590 mm over the next 100 years, depending on the chosen scenario.
Rising sea levels threaten to flood low-lying areas and islands, threaten several hundred million people in densely populated coastal regions – particularly river deltas in Asia, erode shorelines, damage property and destroy ecosystems such as mangroves, salt marches and wetlands that protect coasts against storm events. The impacts may not only be related directly to flooding with increased loss of property and coastal habitats, an increased flood risk and potential loss of life, but may also include inhibition of primary production processes, agriculture and aquaculture through decline in soil and water quality, loss of non-monetary cultural resources and values, impacts on and loss of tourism, recreation, and transportation functions.
Inhabitants of some small island countries that rest barely above the existing sea level are already abandoning their islands, some of the world's first climate change refugees.
Increased risk of heat-related deaths and droughts
The UN climate panel also expects “increasing deaths, injuries and illness from heat waves, storms, forest fires and droughts.” In 2003, for example, extreme heat waves linked to climate change caused more than 20,000 deaths in Europe and more than 1,500 deaths in India.
The scientists warn that in addition to heat-related illness, climate change may increase the spread of infectious diseases and pests that were once limited to the tropics – such as mosquito-borne malaria – may find hospitable conditions in new areas that were once too cold to support them. The World Health Organization (WHO) estimates that climate change may have caused more than 150,000 deaths in the year 2000 alone, with an increase in deaths likely in the future.
As temperatures rise globally, evaporation from land and surface waters also increases, leading to more frequent and more severe droughts in many areas, with potentially devastating consequences for agriculture, water supply and human health. The report stated that it is very likely that the dry season and heat waves would increase, and pointed out that the intensity and length of the dry season has already increased in wider areas since the 1970s, especially in the tropics and subtropics. Thus, the African coast, Mediterranean Basin, South Africa, and parts of South Asia have become drier. Lands affected by drought are more vulnerable to flooding once rain falls. This phenomenon has already been observed in some parts of Asia and Africa, where droughts have become longer and more intense. Associated declining crop yields due to prolonged drought could put hundreds of thousands of people at risk for starvation.
Additionally, more than one-sixth of the world's population live in areas supplied by water sources from glaciers and snow that will “very likely” vanish, causing severe droughts, according to the report.
Hot temperatures and dry conditions also increase the likelihood of forest fires. In the conifer forests of the US for instance, earlier snowmelts, longer summers and an increase in spring and summer temperatures have increased yearly amount of land burned by 650percent and fire frequency by 400 percent since 1970.
Stronger storms and increased storm damage
The IPCC report also indicates that rising temperatures will cause tropical storms and hurricanes to become more intense causing more damage to coastal ecosystems and communities. As sea surface temperatures rise, developing storms will contain more energy, since hurricanes and tropical storms get their energy from warm water. At the same time, other factors such as rising sea levels, disappearing mangroves and wetlands, and increased coastal development threaten to intensify the damage caused by hurricanes and downpours.
Projected climate changes due to global warming have the potential to lead to numerous and varied future large-scale and possibly irreversible effects on the environment and for human life at continental and global scales. Most of the consequences of global warming would result from one of three physical changes: sea level rise, higher local temperatures, and changes in rainfall patterns that would directly lead to flooding of low-lying coastal areas, glacier retreat, and altered patterns of agriculture, but predictions for secondary and regional effects also include more frequent and intense extreme weather events, an increased spread of infectious diseases with drastic economic impact.
Besides marginal positive benefits of global warming, significant negative impacts are projected, that drive most of the scientific and political concern about global warming, leading to political activism advocating proposals to mitigate, eliminate, or adapt to it.
1) IPCC, 2007: Summary for Policymakers. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 7-22.
2) Understanding and Responding to Climate Change, An Overview from the National Academy of Sciences; http://dels.nas.edu/dels/rpt_briefs/climate-change-final.pdf