Local Impacts of Global Climate Change

The overarching theme of this blog has so far been to exemplify the climatic characteristics of the city of Bangalore and how certain key variants of the surrounding natural environment, both on the surface and in the atmosphere, amalgamate to construct the cities unique climatic profile. However this profile is not unconditional, it is not a stagnant cyclical pattern that can be predicted with any actual certainty in future trends.  Rather it is a stage in the ever-changing dynamic of planetary meteorological conditions, which has seen vast extremes on both ends of the climatic spectrum.

Through extensive research from an assortment of scientific disciplines, climate variablity is now a near undisputed scientific truth.  Verification occurred by utilizing proxy indicators as tools to determine the historical climatic record through the examination of uninterrupted and preserved mediums, to replicate a direct measurement of climatic conditions. For example the climatic past can be assessed by taking sample cores out of ancient trees.  The cores reveal the annual growth of the tree through examination of the size of each individual ring, providing insight on the annual climatic conditions of that particular site.  Another means in determining conditions are core samples taken from the oceans and large bodies of water.  These sediment samples preserve pollens and other plant materials which are undisturbed from surface conditions and wave actions at water depth.  As important as these core types are for localities and the geologic near-term, core samples taken from ice sheets and glaciers provide the most extensive knowledge of paleoclimatologic conditions. The most prolific of these is the Vostok core taken from Antarctica.  This particular core is the largest of its kind, and provides invaluable data covering over 400,000 years.  This data is derived from encapsulated air bubbles found within the ice, which through analysis determines the atmospheric composition, and greenhouse gas concentrations. The core also provides insight in the amount of precipitation recieved, temperature trends, as well as solar activity on the continent, which is a proven representative of the annual global conditions of the past.  Besides cores, other means of determining historic records include the makeup and deviations of continental margins of the sea floor.  The analysis of the geologic features show historic exposure to wave erosion points, as well as graduated steppes which determine previous historic sea levels.  In conjunction with variation in sea level rise and fall, is the presence and remnants of periods of glaciation. Records can be ascertained both temporally and spatially of glacial periods from examination of present day geological compositions that modified the topography under the glaciers extent.  This is made possible because of the sheer force of an advancing and retreating glacier, which creates and leaves behind stratifications in rock such as granite, and depositions of materials hundreds of miles from their origins.

Whether or not global warming is occurring is not the true emphasis of the debate, rather it is centered upon whom or what is responsible for these trends and to what extent will these trends continue. The source of global warming is basically divide into two factions, those that believe global warming is nothing more than a high point in a natural climatic cycle, which has been occurring since the inception of the earth, and those that believe that the trend is being caused by, or at least, amplified by anthropogenically induced forces.  Those that reason warming is a natural cycle, point to prehistoric records that surpass that of the present, an unreliable temperature record, and an anomalously high instance of solar activity. The opposing view, points to the vast increase in gases such as carbon dioxide, methane, and ozone since the industrial revolution which has led to a greenhouse effect that readily allows solar radiation into the atmosphere, but not out. These opposing views result in models that see warming either continuing on linear path than falling off, or on an exponential path that will completely alter the world’s climate.

As technological advancements are continually made, the present knowledge of historical climate trends continues to be reinforced and advanced.  This also holds true for the detail and scope of global climatic observations of the present day.  Documentation of weather data for most of the “developed” world has been relatively comprehensive for the past century and the “developed”, “developing” and “underdeveloped” world continually improve upon the degree and accuracy of worldwide weather data. This rapid expansion of knowledge has afforded a foundation for an established field that focuses on the prediction of future climatic conditions. However it is a field that is by no means unified, and has been the focus of heated debate for the past several decades.

The above data shows the steep linear trend of CO2 levels found at the Mauna Loa Observatory on the Big Island of Hawaii.  The site is considered nearly ideal as it has limited influence from local pollutants.

Few experts in the field of climatology will deny the fact that the world is presently experiencing an overall warming trend.  Data collected from the past century shows an average global increase in temperature amounting to 0.74 degrees Celsius, with Polar Regions and certain sub-tropical locations increasing over 2 degrees Celsius in the same period.  Adding to the concern is that the warming trend has been most pronounced in the past few decades.  According to the Intergovernmental Panel on Climate Change (IPCC) the period from 1995 to 2006 experienced eleven of the twelve warmest years on record.  More recent data has shown every year of the 2000’s (besides 2008)  making the top ten, and 2010 now tied for the warmest year on record with 2005, and 2011 being the ninth warmest year in recorded observational history. The predictions for Bangalore and the surrounding region range from an minimum increase in mean temperature of 2.7 ̊ Celsius, to a maximum increase of 4.7 ̊ Celsius by the end of the century.

By definition models are smaller scale representations of real world scenarios and systems, which cannot possibly account for the varying components that make up the latter. Climatic models are no different and often produce vastly different results. Some show only slight changes in the environment while other models of worst-case scenarios would see a dramatic increase in extreme weather events, erratic periods of hot and cold, wet and dry, and a rising sea level that would inundate many of the world’s most populous areas.  For our purposes an average will be used to determine the potential direct affects on Bangalore, and the potential affects that may not be as apparent.

  In even the most extreme cases, the possibility of Bangalore being directly affected by rising sea levels is impossible. In a situation where all of the world’s ice sheets and glaciers were melted and the thermal expansion of water is at its maximum, the sea level would be approximately 100 meters higher than present, an amount that is still over 700 meters lower than the cities lowest elevation.  However, a more feasible sea level rise of 20 meters would displace upwards of 400 million people, and a rise of 10 meters would inundate the Indian cities of Calcutta and Mumbai with water, leading to catastrophic social and economic consequences. A recent study by Jawaharlal Nehru University of India projects a 1 meter rise in sea level would displace 7,000,000 Indians.  Nevertheless the models presented by the IPCC predict a maximum rise of 0.59 meters by the end of the century.

The IPCC models for precipitation extensive variability with estimates ranging from a pronounced decline to significant increase.  For the region of South Asia they averaged these models to have a range of plus or minus 11%, which is what is displayed above.  

Another concern of global warming is that of an increase in extreme weather events. The level of confidence in an increase or decrease in magnitude and frequency of such events varies, depending on the source and location.  Either way it could prove disastrous for Bangalore.  A 2009 study conducted by the Scripps Institute of Oceanography, Oregon State University, and the Desert Research Institute of Nevada has correlated abrupt shifts in world climate with a southward shift in seasonal South Asian monsoons.  A significant reduction in vegetation growth was seen when comparing stalagmites in China with equivocal ice core samples, which researchers surmised, was caused by rain falling in the Indian Ocean rather than on the continent, a scenario that would jeopardize the food security of millions.  However recent trends have shown the opposite to hold true.  The intensity, frequency, and magnitude of monsoonal rains have been steadily increasing at a rate of 10% since 1950, frequently leading to catastrophic flooding.   One such example was in 2009, when 240 people were killed just north of the city, and over 100,000 were left homeless after a four day rain event which followed a period of prolonged drought. Flooding in the region would likely be compounded from increased river flows from melting snow pack, leading to a variety of issues, including disease, and agricultural and structural damage.  Another concern in the region is the frequency and magnitude of tropical cyclones, which rarely directly affect the city, but always affect it indirectly.  Though trends show otherwise, many predict an increase of tropical cyclone events, which have historically been some of the world’s worst natural disasters. Finally the last and potentially most devastating effect of global warming may be intense and prolonged heat waves, a scenario that could result in hundreds, if not thousands of immediate deaths per year, as well as an untold amount of deaths from the loss of available food resources.

The above diagram shows the amount of cylcones that have made landfall on the Indian Sub-Continent from the years 1891-2009.  The green represents cyclonic disturbances (31 KM/h to 61 KM/h), the yellow tropical cyclones (62 KM/h to 87 KM/h) and the red representing severe cylclones (88 KM/h and above). Note the trendlines for the above and following graphs.

Unlike the decreasing trend for all types of cyclones that reached landfall, those based in the Arabian Sea have increased overall in the past century.

The cyclones found in the Bay of Bengal are by far the most abundant of the three.  As the second order polynomial trendline shows a peak was seen from the mid 1940's to the mid 1960's, with a steady decrease since.

The nation of India is attentive to these potentially catastrophic outcomes and has made a conscious effort to reduce their impact on climate change.  The country has committed itself to a 20% to 25% reduction in energy usage by 2020 and recently has proposed their 12^th five year plan to reduce GHG emissions.  While the nation currently spends an estimated 2.8% of its gross domestic product on climate change programs, this is still well short of projected required amount needed to fulfill their 2020 goal. Mitigation efforts include the implementation of solar farms, rainwater collection sites, community organized drainage cleaning to reduce the magnitude of floods, and the regrowth of mangrove forests that act as both carbon sinks as well as protective barriers from tropical cyclones.

Though the efforts made by the Indian Government to mitigate and adapt to climate change are noble and well intended programs, the effort may be misplaced. The country is currently ravaged by rampant poverty, much of which is extreme.   This correlates with the high level of illiteracy among its people as well as burgeoning population that susceptible to starvation should food shortages occur from events perpetuated by climatic change.  The country of India and the city of Bangalore are rich in natural and human resources, but if a perpetual cycle of poverty continues to occur, the country and city will always be subjected to an unnecessary risk.

 

 

Sources

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Lutgens, F. K., & Tarbuck, E. J. (2007). The Atmosphere: An introduction to meteorology. Upper Saddle River: Pearson Prentice Hall.

Manjaro, C. (2011, October 04). Air Pollution is Stunting India's Monsoon. Retrieved April 02, 2012, from The Watchers: http://thewatchers.adorraeli.com/2011/10/04/air-pollution-is-stunting-indias-monsoon/

McKnight, T. L., & Hess, D. (2008). Physical Geography: A landscape appreciation. Upper Saddle River: Pearson Prentice Hall.

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Historical Climatology of Bangalore and the Growth of the City

As with all the locations of the world, an accurate description of a localities weather and climate regime must consider the various scales that influence it and make each individual location unique. In meteorology, scales are distinguished spatially as either micro, meso, or macro, from smallest to largest respectively, and the latter of which will be discussed in the next post.  So far, this blog has focused extensively and nearly exclusively on the meso (regional) scale of the Indian subcontinent and surrounding environments.  This includes discussion of Bangalore’s position in relation to the Indian Ocean and the Asian Continent, as well as the ITCZ and the Himalayan Mountains. Combined, these factors contribute to a generalized regional weather system, which is often portrayed on maps using classification systems such as Koppen-Geiger. However, each specific location has its own unique weather and thus climate.  These variations’s can be seen from city to city, city to rural, or wholly within the city itself, at the micro-scale.  In the case of Bangalore the most pronounced factor that is currently changing, as well as differentiating its climate from its neighbors, is the near exponential population growth and the subsequent expansion of the city proper. Known as an urban heat island effect, the city itself tends to be warmer than the surrounding environments. Also precipatation tends to be slighltly higher on the windward side of the city, a situation which would not have occured otherwise. The cause behind urban heat islands is belevied to be from an increase in the albedo of built environments, a decrease in evapotranspiration, and an increase in environmental air pollutants.

The above records are from the Indian government's Ministry of Home Affairs, the branch which is responsible for the decadal census of the country.  This type of growth is seen throughout the country  and India is expected to surpass China sometime in the next couple of decades as the most populous country in the world.  The city of Bangalore has several times been the fastest growing major city in the country and consistently been among the fastest growing cities in the world.

The above graph is the historical mean high and low temperatures for Bangalore along with the annual precipitation. Though high temperatures have remained relatively consistent, the mean low has increased significantly from 1901 to 2000. Also take note at the extreme variation in precipitation, from over 100 mm in one year to a half a decade straight of no recordable amount.

The historical records for July show an upward trend in both the mean highs and mean lows for the month and with an almost 1.5 degree Celsius increase in the average low over the century long period.  It should be noted that the reason for the lack of information of the most recent decade is the propriety stance of the Indian Meteorological Department.  Generalized and often incomplete information can be obtained from mostly US and European agencies and entities, but the inconsistent nature within and between these highly regarded meteorological centers has left me no choice but to omit their data.  These policies are currently being questioned by academia, businesses, and individuals within the country and abroad.  A slide show can be found at the end of the post for further information and action currently taking place.

The most widely used climate classification system, the Koppen-Geiger system was created in the latter part of the 19th century and has been expanded upon several times since.  In terms of scale, at best it could be considered effective on the meso level, however should probably be only considered at the macro-scale as seen above.

Zooming into the regional meso-scale it can be seen that Bangalore falls along the border of Highland Subtropical (CWb) and Humid Subtropical (CWa), however other sources have placed the city in a warm semi arid or tropical wet-dry regime. These definitive lines and descriptions are why it is important to consider all scales when describing a specific location.  As mentioned before historical analysis has shown that the city center has different weather patterns than the surrounding environments, a discrepency that continues to increase with continual urbanization.  

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Ward, A. D., & Trimble, S. W. (2004). Environmental Hydrology. Boca Raton: CRC Press.

Withgott, J., & Brennan, S. (2008). Environment: The Science Behind the Stories. San Francisco: Pearson Benjamin Cummings.

Climate data in india - Open and Closed

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