Catastrophic nature of Global Warming

Professor S. Antony Norbert
Department of Geography
University of Colombo

The phrase ‘Global Warming’ has become familiar recently as environmental issues have hit the headlines. Within the past decade, there has been a considerable rise in public awareness and interest in climate change and in the possible impact of human activities on global climate.

Such interest is particularly acute amongst environmental scientists, but is also prevalent amongst politicians, economists and some industrialists and has resulted in continuing attention in the media.

The focus of attention has been upon the present and continuing effects upon climate of both domestic and industrial fuel use and of other process both agro-environmental and industrial that lead to the release into the atmosphere of so-called ‘greenhouse’ gases. A recorded rise in temperature this century is mainly attributable to human activities and this rise will both accelerate and continue until well after greenhouse gas emissions are stabilised.

Records show global temperatures increasing: consolidated data from selected terrestrial stations and marine sea-surface temperature (SST) records round the world reveal that the seven warmest years this century have occurred since 1980.

The recorded rise in temperatures has been linked to an estimated 30 per cent rise of carbon dioxide concentrations in the lower atmosphere over the last 200 years. As the carbon dioxide concentrations in the atmosphere continue to rise, there might be major temperature rises and perhaps even catastrophic climate changes in the next century.

Changes in world temperature

The climate has changed significantly in historic times. The little ice age that lasted from about 1550 to 1850 was a period when the global climate was cooler and winters were particularly cold. Since the 19th century there have been temperature data available from weather stations throughout the world.

But it is difficult to compile an accurate picture of changes in world temperature over the last century due to various problems and errors. Overall there has been a worldwide warming of about 0.5 degree C since the end of the 19th century. During this time there have been two periods of rapid temperature increase, one between 1910 and 1930 and the other between 1970 and the present.

The 1990s was the warmest decade and 1998 the warmest year. On average, between 1950 and 1993, night-time daily minimum air temperature overland increased by about 0.2 degree C per decade. Warmest episodes of the El Nino Southern Oscillation (ENSO) phenomena have been more frequent, persistent and intense since the mid 1970s, compiled with the previous 100 years.

In recent years, the large body of evidence that shows human activity is changing the global climate, raising temperatures and affecting ecosystems around the world. The Earth has warmed by approximately 0.75 degree C since pre-industrial times.

Global average temperatures have increased by 1.1 degree F over the last century - warming faster than any time in the last 1,000 years. As a result, the 1990s were the hottest decade in the past 1,000 years. There is overwhelming consensus that this is due to emissions of greenhouse gases, such as carbon dioxide (CO2), from burning fossil fuels.

Examination of ice cores shows that there is more CO2 in the atmosphere than at any time in the past 600,000 years. Between 1960 and 2002, annual anthropogenic global emissions of CO2 approximately tripled. They rose by about 33 percent since 1987 alone. Warming in this century is projected to be between 1.4 and 5.8 degree C.

After reviewing hundreds of studies that used data and climate models to examine past and future changes in climate extreme, a team of scientists, led by David R. Easterling of NOAA’s National Climatic Data Centre reached a conclusion that our climate changes, extreme weather events such as droughts, floods, heat waves, heavy rainfall, tropical storms and hurricanes are expected to increase.

This trend is likely to become more intense in the years to come both as the climate continues to change, and society continues to become more vulnerable to weather and climate extremes. Scientists are increasingly concerned about the possibility of abrupt climate change, including reductions in ocean currents, such as the monsoon seasons, which would affect food security for billions of people.

Today, most mainstream scientists and scientific bodies agree that heat-trapping gases like carbon dioxide - produced mainly from the burning of fossil fuels in cars, power plants factories and homes have caused temperatures to rise around the globe.

Carbon dioxide, the major greenhouse gas, is currently found in the atmosphere in a concentration of 379 parts per million, and is almost certain to reach 540 ppm sometime in the next 40 to 50 years, according to the Intergovernmental Panel on Climate Change (IPCC). It could reach 800 to 1000 ppm before the end of the century.

According to the report by the IPCC, a doubling of carbon dioxide in the atmosphere would produce a global temperature rise ranging from 3 to 8 degrees F.

Humans are the dominant force behind the sharp global warming trend seen in the 20th century. The natural factors like volcanic eruptions and fluctuations in sunshine, which were powerful influences on temperatures in the past centuries, can account for only 25 percent of the warming since 1900.

The rest of the warming was caused by human activity, particularly rising levels of carbon dioxide and other heat-trapping gases. The natural variability plays only a subsidiary role and the most parsimonious explanation for most of the warming is that it is due to the anthropogenic increase in greenhouse gases (GHGs).

The impacts of climate change is already visible. Examples include: the shrinking Arctic ice cap; accelerating sea level rise; receding glaciers worldwide; thawing permafrost; earlier break-up of river and lake ice; increasing intensity and duration of tropical storms; lengthening of mid-to high-latitude growing seasons; and shifts in plant and animal ranges and behaviour.

Sea level rise

In the past 100 years, global sea level rose between 1 and 2 millimetres a year. Since 1992 the rate has increased to about 3 millimetres a year, primarily through thermal expansion of warming oceans and freshwater flowing into the oceans from melting ice.

Melting ice is responsible for a significant portion of the observed sea level rise, with the Greenland and Antarctic ice sheets the largest contributors. The Greenland Ice Sheet is melting faster than new ice is being formed.

Scientists know that warm sea surface temperatures provide the energy source for tropical storms, but many other factors influence whether hurricanes form and which way they go. Scientists projected current climate conditions for 2080 using by nine different global climate models.

Comparing the results, they found that global warming would increase hurricane intensity by 8 to 16 percent, with rainfall increasing by 12 to 26 percent within 60 miles of the storm centre.

Meanwhile, sea level rise due to global warming will push shorelines inland by 400 feet or more in low-lying areas, making storm surges even more damaging.

Land degradation

The severe droughts and forest fires of recent years in the regions of Mediterranean Europe, is threatening the livelihoods of 16.5 million Europeans. There are 300,000 square kilometres of territory currently affected.

Degradation is mainly due to human activities such as over farming or land clearance, although drought also degrades the quality and productivity of soil and vegetation. The average temperature of major Asian cities could rise by 3 to 10 degrees Celsius by the end of the century while longer droughts and flooding threaten rural areas.

Antarctica

Antarctica is a continent surrounded by ocean. It is the coldest, windiest and driest continent on earth. Close to 99 percent of the continent is covered by an ice-sheet with an average height above sea level of approximately 2,500 metres. Antarctic ice sheet has an average depth of around 2000 metres.

The largest depth that has been measured is approximately 4,700 metres. The amount of ice in Antarctica constitutes about 91 percent of the world’s total. If all Antarctic ice were to melt, sea level would rise by more than 60 metres.

Antarctica has no native terrestrial vertebrates, but large populations of marine birds and seals which go there to breed. A large proportion of the world’s seals are found in the ocean surrounding Antarctica. In the summer season both toothed whales and baleen whales are present in the Antarctic marine environment.

Around 45 species of nesting birds are found south of the Antarctic Convergence, all of which are connected to the marine ecosystem. Penguins constitute 85 percent of the biomass of Antarctic sea birds. In the Antarctic, three large sections of ice shelves in the Antarctic Peninsula have collapsed over the past 11 years.

Arctic sea ice

There are important geographical and political distinctions between the Arctic and Antarctic. The arctic is a partially-frozen ocean surrounded by a diversity of landscapes influenced by seasonal snow cover and permafrost, including ice, sparsely-vegetated barren lands, tundra, wetlands and forests. The Arctic Ice Cap consists of glaciers, ice sheets, icebergs and sea ice.

Sea ice covers approximately 7.5 to 15 million square kilometres of the Arctic Ocean, with an average thickness of about three metres. During the summer, 10 to 15 percent of the Arctic Ocean is not covered by ice. Greenland Ice Sheet is the largest Arctic glacial mass.

It constitutes 10 percent of the world’s total freshwater reserves. Melting of sea ice will not increase sea levels, but if all the Green ice were to melt, the sea level in the world’s oceans would rise by seven metres. The Arctic is warming twice as fast as the global average.

NASA satellite images show a 20 percent decline in summer arctic sea ice since 1979, while Antarctica glaciers are melting faster than expected accelerating sea level rise. Since 1980, between 20 and 30 percent of sea ice in the European Arctic has been lost. Some climate models project that there may be an almost complete loss of summer sea-ice in the Arctic before the end of the century.

If this happens, polar bears are unlikely to survive as a species. The Arctic Climate Impact Assessment found that in Alaska, western Canada and eastern Russia average winter temperatures have increased as much as 40 to 70F in the past 50 years. Hunting has become more difficult and dangerous due to less reliable sea-ice conditions.

Highland glaciers

In China, highland glaciers are shrinking each year by an amount equivalent to all the water in the Yellow River. The Chinese Academy of Science says that seven percent of the country’s glaciers are vanishing annually. By 2050, as many as 64 percent of the country’s glaciers will have disappeared. An estimated 300 million people live in China’s west and depend on water from glaciers for their survival.

Coral reefs

Coral reef is thought to host the most species-rich communities of the marine environment. They are comparable to tropical rainforest in that damage to their ecosystems may affect thousands of species adversely.

Two thirds of all marine fish species are associated with tropical reefs where many human societies are depended on coral reefs for food, sport, protection of shorelines from storm damage, and tourism. All the nucleus of the coral reefs that have photosynthetic plant cells living symbiotically in their tissues.

This plant-animal partnership is responsible for an efficient recycling of nutrients. Geologically, reefs are made up of calcium carbonate produced by corals and other organisms, most notably coralline algae that has accumulated layer upon layer over thousands of generations.

Reef communities are dependent on this reef structure for substrate and shelter and also on the reef’s primary production, to which the corals and algae make substantial contribution.

In the tropical waters, no reef occurs where the waters are too deep, too muddy, too diluted by fresh water, or too hot. No coral reefs occur where temperatures exceed 30 degrees C for extended periods. It is also noted that many coral reefs are already near their upper thermal limit, at least for some months of the year.

Thus, the small increases of 20-30 degrees C that are predicted for the surface waters of tropical oceans have profound implications for the structure, function, and distribution of reef ecosystems.

At least three major effects of temperature increase on coral reef may be identified. The first is physiological. Corals may expel their symbiotic algae in response to heat stress so that they appear bleached. Without those cells, corals cannot grow, and unless the algae become re-established, the corals die within a few months.

Warming of tropical eastern Pacific waters contributed to wide-spread coral bleaching and death in 1982-83, and surface water temperatures above 30 degrees C are thought to have been responsible for the wider spread bleaching of corals in the Caribean Sea in 1987 (Roberts, 1987).

Second, mechanical damage to reefs could increase. If corals die and reef growth stops, the reef will become more vulnerable to erosion. Further more, warming of tropical oceans may increase the frequency of hurricanes. Mechanical damage due to storms is a major source of coral mortality. Hurricanes can strip all living corals from long stretches of reef.

Third, thermal expansion of ocean water, among other factors, causes elevation of sea level. The rate of sea level rise may affect the extent, structure and functioning of coral reef communities.

Elkhorn, staghorn and fused-staghon coral, which live in the Caribbean and off the southeast coast of Florida, have declined up to 98 per cent in the past 30 years, largely due to global warming.

New research shows that carbon dioxide is a direct threat to corals because ocean water becomes more acidic (lower pH) as it absorb some of the CO2 emitted by power plants, automobiles and other sources. With corals already suffering from rising temperatures, the additional stress of falling pH could push them over the edge.

The oceans have absorbed approximately half of the CO2 produced in the past 2,000 years, producing carbonic acid and lowering the pH of surface seawater. This could affect the process of calcification by which animals such as corals and molluscs make their shells from calcium carbonate.

Agricultural Industry

Although crop yields may increase in some areas due to climate change, the negative effects are likely to dominate as warming increases. Africa is especially vulnerable, and studies warn that there may be a significant increase in hunger.

Poor communities are most directly dependent for their livelihoods on a stable and hospitable climate. They often rely on rain-fed subsistence agriculture, and are deeply dependent on climatic phenomena, such as the Asian monsoons.

A comprehensive regional study of the impacts of global warming in California shows that higher temperatures and summer water shortages would seriously harm California’s $30 billion agricultural industry. Alpine meadows in the Rocky Mountains to disappear, sugar maple trees to vanish in the Northeast, and greater risk from storm surges in the Southeast. Rising temperatures will also exacerbate water shortages in the west.

As glaciers melt in the world’s great mountain ranges, water supplies to rivers will be affected. In Europe, eight out of nine glaciated regions show significant retreat. Between 1850 and 1980, glaciers in the European Alps lost approximately one-third of their area and one-half of their mass.

This is also bad news for everyone who enjoys the fruit of their vines. The quality of California wine grapes would be degraded by excessive temperatures during ripening.

More bad air days

Hotter temperatures caused by global warming will speed formation of the lung-damaging pollution commonly known as smog, significantly reducing the number healthy air days enjoyed by residents in more than a dozen cities in the USA. The residents of the inner city are particularly vulnerable to the affects of climate change and global warming.

The greatest threat is from heat waves. Exposure to excessive heat caused over 8,000 deaths in the United States between 1979 and 1999. Extreme heat waves caused more than 20,000 deaths in Europe and more than 1500 deaths in India during 2003. Higher temperatures also elevate the level of ozone smog in urban areas, which contributes to excess mortality and triggers more asthma attacks.

Conclusion

The scientific findings released over the past few years show the humankind’s impact on earth’s climate. Given this growing body of evidence, we must act now to reduce pollution from vehicles and power plants. By deploying already available technologies it is possible to prevent a doubling of carbon dioxide in the atmosphere during the next 50 years and avoid the most dangerous threats from global warming.

The British Government has committed to reducing its emissions of heat-trapping gases by 60 percent from 1990 levels by mid-century and urging other industrialized countries to adopt the same goal. Any delay would be dangerous, because an additional warming of merely one degree Celsius could be enough to trigger the eventual disintegration of ice sheets in Greenland and parts of Antarctica.

The international community needs to work together immediately, not only to stabilise the level of heat-trapping greenhouse gases, but also to develop alternative technologies in order to move away from our dependence on fossil fuels.

Delaying action will only make it “more disruptive and more expensive” to deal with global warming. Substantial reductions in emissions can come from improvements in fuel efficiency of cars and trucks, policies that require energy efficiency and the use of renewable energy, and long-term investments in new technologies like hydrogen fuels and bio fuels.

Carbon dioxide is the main greenhouse gas (GHG), and slowdown of its emissions must have priority. It will be a growing issue in international relations for decades. ‘Kyoto’ gives too little or no weight to gases such as methane, the trace gas HFC-134a, ozone and the precursor gases that form ozone.

The slowdown in the growth rate of the GHGs contribution to global warming from the peak in the 1980s is due mainly to the phase out of CFCs as dictated by the Montreal Protocol. This success could be diminished by increases of other trace gases not controlled by the Montreal Protocol. Therefore, it is well worth extending the Montreal Protocol machinery to phase out many of these trace gases.

More than half of all humanity has probably always lived within coastal areas of the world, and that proportion is increasing rapidly. Human activities have already caused extensive alteration of natural coastal ecosystems, which can ill afford further damage. Therefore, natural and international efforts to protect coastal areas should be given the highest priority, and long-term plans should include provisions for dealing with climate change.

Climate change cause profound changes in the ecology of marine systems, but also climate change will add stress to systems that are already experiencing increasing and often severe disruption from other human activities, including pollution, habitat destruction, and over harvesting of the seas.

All of the changes that we have mentioned have consequences not only for species and ecological diversity but also for the human economic future. Change in the abundances or geographical availability of fishery resources, for example, will have great human impacts. The consequences will be ever larger if warming affects basic ecological processes such as primary productivity, reef building, and the lifestyles communities.