Prof Sanath P Lamabadusuriya MBE
In the recent past there have been major natural disasters such as floods, droughts, cyclones, earthquakes, landslides, tsunamis, forest fires etc. affecting many countries. There is increasing evidence that global warming (GW) is directly linked to the increasing incidence of natural disasters, and climate change (CC). Natural disasters and CC have affected millions of lives globally; many epidemics of infectious diseases have occurred, new diseases have emerged, hundreds of thousands have perished and survivors have been left with a heavy burden of physical handicap and psychological problems.
The Industrial Revolution began in the 1800s with the discovery of the steam engine and later the internal combustion engine. The steam engines that are powered by coal and internal combustion engines that are powered by oil, led to an exponential increase in the usage of earth's fossils during the last two centuries or so. As a result, vast amounts of carbon dioxide (CO2) locked up below the earth were released. With the spread of agriculture and industrialisation, deforestation followed. Many green house gases (GHGs) such as CO2, methane, water vapour and nitrous oxide (N2O) occur naturally in the atmosphere. The synthetic (man made) GHGs that are released as a result of usage of fossil fuels are CO2, methane (CH4), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). These gases are considered to be at least partly responsible for GW, leading to a rise in temperature which may have catastrophic consequences for life on earth. Although CO2 has the least GW potential of the 5 gases, it has a lifetime of almost 100 years. In the atmosphere, water vapour, CO2 and other GHGs absorb some of the thermal radiation leaving the earth's surface. Plants have the capacity to absorb and trap CO2; but with deforestation there is less vegetation around to do so. Thus, with increasing production of CO2 through utilization of fossil fuels, more transmitted heat from the earth's surface is trapped leading to GW. The average global temperature has increased gradually during the last two hundred years.
GW has resulted in the melting of the polar ice caps, and rise in the sea levels. This would eventually result in the increase of ocean volume at the expense of land volume. GW has a major impact on CC such as increase in temperature, extremes of climate, changes in the quantity and distribution of rainfall (both spatial and temporal) and rise in sea levels. At present, there is near unanimous scientific consensus regarding the hazards of GW, and the WHO estimates that CCs of the past 30 years claimed over 150,000 lives annually, obviously not all associated with communicable diseases.
Ecosystems are affected by GW. Higher temperatures enhance microbial proliferation which may ultimately result in outbreaks of food-borne epidemics. Extreme weather related disasters have been followed by food, water and vector-borne disease outbreaks. Climatic variations also have a profound effect on vectors, as they affect reproduction and survival rates. Temperature thresholds of pathogens and their vectors are well defined. A range of epidemics have been associated with CCs such as dengue (Sri Lanka, Pakistan) pulmonary hanta virus syndrome (USA), Rift valley fever (Kenya), meningococcal disease (Saudi Arabia) and leptospirosis (Sri Lanka). Regarding tick-borne encephalitis and Lyme disease, there is an ongoing debate on the precise role of climate influencing a detected increase. Malaria is now spreading to new regions and higher altitudes, however, it remains controversial whether GW is the major cause as such changes are determined by many other factors such as air travel as well.
Emerging infectious diseases are often zoonotic in origin (eg rodent populations may increase with CC). In Sri Lanka the vector of dengue viral fever, the Aedes mosquito, has been detected to breed at higher elevations. GW leads to migration of large communities. When they are displaced as a result of worsening weather patterns, inundations or desertification of crop land, they may import infections as environmental refugees to their often over-crowded home areas, as seen in the African continent. In the summer of 2003, due to an extreme heat wave in South West Europe, when the mean temperature was + 3.50 C above normal (hottest in 500 years), during a 2 week period in August, there were 22,500 to 45,000 deaths. Risk of such heat waves have doubled by 2003 due to human induced CC. There have been milder heat waves in Greece and Italy subsequently. India has experienced 18 heat waves between 1980 - 1998. In India there were 1300 deaths in 1998 and 3000 deaths in 2003. Bangladesh experienced a heat wave in 2001 which caused deaths among rickshaw pullers and metal workers. Since 1850, the period between 1995 and 2007 have been the warmest 12 year period.
Changes in complex ecological systems are an indirect effect of CC. The ecology may change resulting in the range and activity of vectors of diseases such as dengue, malaria, avian flu, Chikungunya etc. There would be changes in the environment to facilitate transmission of water-borne diseases such as shigellosis and cholera. Geographic Information Systems (GIS) can be used to store information and integrate data analysis, so as to predict outbreaks of dengue fever and identify potential “hot spots” as was recently carried out in Mawanella. Possibly there are also few beneficial effects of CC on communicable diseases such as decreased influenza infections in cold climates but data are not conclusive. The highest disease burden is expected to be in regions with the lowest capacity of adaptation according to all predictions and models.
What are the possible solutions to GW, CC and its consequences? The biggest producer of GHGs, which is the USA, is not a signatory to the Kyoto Protocol (KP), regarding it's prevention. KP is an international agreement setting targets for industrialised countries to cut their GHG emissions. This protocol was agreed and ratified in 1997 by most countries except for USA and Australia. Signing of KP is symbolic and it's ratification carries a legal obligation and effectively becomes a contractual agreement. The target was to cut their combined emissions by at least less than 5% by 2008 - 2012. Australia signed the agreement later; however, USA has not done so as yet. The main reason for abstinence is due to the potential damage to their national economy. The agreement acknowledges that most developing countries (except China and India) contribute least to climate change, but will quite likely suffer most from its effects. Countries are also able to gain credits for activities which boost the environment's capacity to absorb carbon. These include tree planting and soil conservation, and can be carried out in their own country, or by that country working in a developing country.
It is heartening to note that in some industrialised countries which are environmentally conscious, Green Parties are emerging; in some parliaments there are elected members. If this movement gathers momentum, there may be a slowing down of GW. In some countries such as Australia, although fossil fuels such as coal are found in abundance, environmentally conscious individuals are using solar panels to generate electricity for their own needs; the excess power that is generated is sold to the national grid. Solar panels made in China are being exported to the USA at a very competitive price. At present generation of power through solar panels is expensive. However, in the long run it is cost saving.
The writer is the President of the Sri Lanka Medical Association and Emeritus Professor of Paediatrics of the University of Colombo.
http://www.dailynews.lk/2011/12/26/fea01.asp
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