FOR AGENDA 21 CHAPTER 9
Addressing uncertainties (9A)
Sustainable development: energy, transportation, industry, resources/land use (9B)
Risks from new technologies
Ozone depletion (9C)
Damage to the ozone layer
Atmospheric pollution (9D)
New air pollution problems
As if each of the major atmospheric
problems were not enough by themselves, they can interact and reinforce
each other. Recent research has shown that acid rain and global warming
can greatly magnify the effects of ozone layer thinning. In Canada,
regional warming has reduced precipitation and thus dissolved organic carbon
inputs to lakes, while acidification reduces the productivity of some plants.
Together these can raise ultraviolet penetration in lake water from thinning
ozone by up to 800 percent, causing increasing damage to lake ecosystems
(Schindler, et al., 1996).
The IPCC third scientific assessment (IPCC 2001) shows that there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities. Since the IPCC’s 1995 Report confidence in the ability of models to project future climate has increased. For example, there is now a longer and more closely scrutinized temperature record. Reconstructions of climate data for the past 1,000 years, as well as model estimates of natural climate variations, suggest that the observed warming over the past 100 years was unusual and is unlikely to be entirely natural in origin. In addition, detection and attribution studies consistently find evidence for an anthropogenic signal in the climate record of the last 35-50 years. However, there are still many remaining gaps in information and understanding about climate change.
An increasing body of observation gives a collective picture of a warming world. Globally it is very likely that the 1990s were the warmest decade, and 1998 the warmest year, in the instrumental record, since 1861. New analyses of data from tree rings, corals, ice cores and historical records for the Northern Hemisphere indicate that the increase in temperature in the 20th century is likely to have been the largest of any century during the past 1000 years, and it is likely that the 1990s were the warmest decade and 1998 was the warmest year (IPCC 2001).
In the mid- and high-latitudes of the northern hemisphere, it is very likely that snow cover has decreased by about 10% since the late 1960s, and the annual duration of lake- and river-ice cover has shortened by about two weeks over the 20th century. It is likely that there has been about a 40% decline in Arctic sea-ice thickness during late summer to early autumn in recent decades.
Since 1750, the atmospheric concentration of carbon dioxide has increased by 31% from 280 parts per million to about 367 ppm today. The present CO2 concentration has not been exceeded during the past 420,000 years and likely not during the past 20 million years.
The globally averaged surface temperature is projected to increase by 1.4 5.8°C from 1990 to 2100. This is higher than the 1995 Second Assessment Report’s projection of 1 - 3.5°C, largely because future sulphur dioxide emissions (which help to cool the Earth) are now expected to be lower. This future warming is on top of a 0.6°C increase since 1861 (IPCC 2001).
Global average water vapour concentration and precipitation are projected to increase. More intense precipitation events are likely over many northern hemisphere’s mid- to high-latitude land areas. The observed intensities and frequencies of tropical and extra-tropical cyclones and severe local storms, however, currently show no clear long-term trends, although data are often sparse and inadequate.
Sea-levels are projected to rise by 0.09 to 0.88 metres from 1990 to 2100. Despite higher temperature projections these sea level projections are slightly lower than the range projected in the Second Assessment Report (0.13 to 0.94 metres), primarily due to the use of improved models, which give a smaller contribution from glaciers and ice sheets (IPCC 2001).
The string of record warm years and other signs of climate disruption continues the trend already documented in the previous IPCC report and other studies (IPCC, 1995; Pearce, 1995c; Karl, 1998). The greatest temperature increase has been in the southern hemisphere (Salinger, et al. 1994; Bindoff and Church, 1992), and ice shelves are retreating significantly on the Antarctic Peninsula (Johannessen, et al., 1995; Vaughan and Doake, 1996). However, the effects of change are already and will probably continue to be seen in the northern hemisphere as well: according to a report published by the Department of the Environment in the UK, London will be as hot as the Loire Valley within 20 years (Parry et al., 1996). Sulphate aerosols have counteracted warming in industrialized areas of the northern hemisphere, at least on a short-term basis (IPCC, 1995; Pearce, 1995b), but as air pollution is controlled, this effect should diminish.
New evidence also shows that climate can change or oscillate more rapidly than expected, and that deep ocean currents may be part of the control mechanism. Worse yet, a process of ice formation off Greenland which drives one of these deep currents and helps to maintain the Gulf Stream (responsible for the mild western European climate), failed completely in 1994, probably as a result of global warming (Grootes et al., 1993; IPCC, 1995; Wadhams, 1996). The deep waters of the Atlantic, Pacific and Indian Oceans have also warmed in the last few decades (Salinger et al. 1994; Bindoff and Church, 1992; Parrilla et al., 1994). The role of oceans in absorbing carbon dioxide and stabilizing climate may also be affected by changes in plankton populations (Lovelock and Kump, 1994); ocean surface warming off California is associated with a decrease in zooplankton of 80 percent since 1951 (Roemmich and McGowan, 1995), and a significant change in intertidal marine life (Barry et al., 1995), with warm-water species moving up the coast and colder-water species retreating. It is these lateral shifts in temperature patterns that may be the most important signal of global warming. The sea surface has also warmed significantly in the western Pacific off Japan (Japanese Maritime Safety Agency, 1995). However, sea levels are now expected to rise more slowly than predicted earlier, perhaps by 45 cm by 2100 (EPA, 1995; IPCC, 1995).
New studies show that methane emissions from natural wetlands have serious implications for global warming. Methane, an important greenhouse gas, is produced in summer from wetlands in western Siberia, leading to high atmospheric concentrations. In eastern Siberia, methane is produced in the sediments of permafrost lakes, and large quantities of methane are stored in permafrost. Warming in permafrost areas of Siberia and Canada might increase methane emissions to the atmosphere significantly (Dallimore and Collett, 1995).
Climate inertia and the long life of gases mean that the full effects of past emissions will occur even if future emissions are reduced, slowing the effect of emissions reductions. Even if industrialized countries reduce emissions by 30-90 percent, global emissions would reach two to three times 1990 levels, so a slow start is difficult to correct later. There are large margins of error in calculating natural sources and sinks, such that an accurate calculation for terrestrial sources and sinks is not presently possible (ENB, 1997).
The IPCC has assessed regional vulnerability to climate change impacts in 10 regions, because the ability to predict impacts for specific places and times is limited. It concluded that ecosystems, especially forests and coral reefs, are highly sensitive to climate change. Billions of people could be affected by exacerbated problems in drinking water supply, sanitation, and drought. Food production could decrease in the tropics and subtropics, despite steady global production. Significant adverse effects on small island States and low-lying deltas such as in Bangladesh, Egypt and China could displace tens of millions of people with one meter of sea-level rise. Heat stress mortality and vector-borne diseases could increase. Most effects are negative for the most vulnerable developing countries (ENB, 1997).
Much of the controversy about proving the reality of climate change is because the wrong effects are being measured. The effects should appear not as global warming, since the tropics and the poles will show little temperature change, but as global heating expressed by increased variability and shifts in the latitude of biological and climatological features in temperate regions. The tropics will grow wider and the polar regions will shrink. These effects are already being demonstrated (Barry et al. 1995). An increased frequency of the El Niño/Southern Oscillation and other ocean/atmosphere oscillations, and more severe storms, could be a result of increased energy available from global heating. The biggest recent concern, based on coupled ocean/atmosphere models, is of major changes in the oceans, particularly the Southern Ocean, such as more stability in ocean temperature gradients and a reduction of nearly a quarter in ocean fertility over the next 75 years. This would reduce the capacity of the oceans to take up carbon dioxide, thus further accelerating the greenhouse effect (AtKisson, 1997).
In the meantime, while Europe as a whole may possibly stabilize its carbon emissions, this is clearly only the beginning of the effort needed to deal with climate change (EEA, 1995). Many other countries may have serious difficulties meeting their stabilization targets under the Framework Convention on Climate Change.
One positive result of the focus on climate change has been significant progress in methods of climate prediction and impact assessment, particularly with reference to inter-annual changes such as variations in rainfall associated with the El Niño-Southern Oscillation. This is now possible because of increased ocean observations from automatic buoys and satellites, new means of network communications, and the capability to monitor climate anomalies in near-real-time on a global basis. See for example the satellite data on the El Niño phenomenon at the Jet Propulsion Laboratory http://www.jpl.nasa.gov/elnino/. The first global assessment of the 1997-98 El Niño event was held in Guayaquil, Ecuador in November 1998 and adopted the Declaration of Guayaquil. If adequately supported and made operational through the Global Climate Observing System, mechanisms to make such predictions could provide significant economic benefits in many regions (Cane et al., 1994; WMO, 1995).
The energy sector, the driving force for modern civilization, has been giving mixed signals. While oil prices have dropped because of producing countries' desires to maintain income, the latest estimates suggest that global oil production will peak in a decade or two. Falling production will then drive prices up rapidly. On the other hand, changes in technology such as a rapid shift to electric vehicles could cause a fall in demand, which would have severe economic consequences for oil-producing countries. While this would improve air quality in cities, the impact on greenhouse gas production would depend on whether non-fossil energy sources were used to meet the increased demand for electricity (MacKenzie, J., 1996).
Plans by a Russian consortium of aerospace companies to launch giant space mirrors to light up northern cities in the arctic, put forth as a novel way to economize on terrestrial energy consumption, were put on hold in February 1999, when an experiment with a 25-metre reflector misfired. The mirror failed to open, much to the relief of astronomers studying faint objects, who risked seeing their instruments blinded by the light (Ward, 1998).
Furthermore, altering the natural rhythms of light with which organisms have evolved since the very beginning could have caused an ecological disaster. Lunar cycles of light at night are important to many biological processes. For example, the regular appearance of moonlight has been shown to synchronize reproductive cycles, such as in marine brown algae of the Dictyotales, where male and female gametes are borne by separate plants and only precise timing of their development and release by moonlight ensures effective fertilization. Some animals also use lunar rhythms to time their reproduction. The creation of artificial moonlight could have significant ecological impacts, including reproductive failure in some species and their disappearance from affected areas, with consequences all through the ecosystem. Animal behaviour, hormonal balances and plant development are other areas where disruption by artificial moonlight could be expected. With the lack of adequate research in this field, many other unsuspected effects are probable. It would be unwise to proceed with plans for space mirrors without detailed environmental impact assessments and due respect for the precautionary principle.
Satellite measurements in September 2000 revealed that the stratospheric ozone “hole” over the Antarctic had a reached a record 28.3 million square kilometres (some one million sq. km more than the previous record, in 1998). Earlier in the year, ozone depletion over northern latitudes also reached record levels, leading to predictions of a second ozone hole over the Arctic; such an event would expose many millions of people to dangerous doses of ultraviolet-B radiation.
The danger is that ozone-destroying chemicals are long-lasting and take time to travel up to the stratosphere. Chemicals released years ago are still present in the atmosphere and are contributing to today’s peak concentrations.
Meanwhile, global climate change is thought to be slowing the ozone layer's healing process. The warming of the atmosphere near the ground causes the stratosphere to become even colder. Cold stratospheric temperatures, particularly during the early Antarctic spring, catalyze the chemical processes that destroy ozone molecules (UNEP, 2000).
Scientist first suggested in 1974 that man-made chloroflourocarbons (CFCs) might cause ozone depletion. There is now conclusive proof that CFCs and similar chemicals are the cause of ozone depletion in the stratosphere, since chemicals found there could come from no other source (Russell et al., 1996). The reduction and elimination of production of many ozone-depleting substances in industrialized countries under the Montreal Protocol to protect the ozone layer is a major international environmental accomplishment (EEA, 1995). A decrease in levels of ozone depleting substances in the lower atmosphere has already been recorded (Montzka, 1996). However the damage to the ozone layer continues to accelerate, thinning twice as fast as predicted, for reasons scientists cannot explain (MacKenzie, 1995). The next ten years are expected to be the most vulnerable (Albritton, 1995).
The hole in the ozone layer over the Antarctic reached its largest size ever in September 1998. It grew by more than 15 percent, exposing not only Antarctica but a large area of the Pacific and Atlantic oceans and the southern tip of South America to harmful ultraviolet radiation. The ozone reduction was more serious because the polar vortex of high level winds around a cold low-pressure centre was larger than usual, facilitating increased ozone destruction ( WMO, 1998). Major ozone layer losses are now occurring over the northern hemisphere as well, with serious losses since the winter of 1991-92 and a record hole in 1996 lasting two months that doubled carcinogenic ultraviolet rays over an area covering Scandinavia and extending from Greenland to Western Siberia (WMO, 1996). The lowest reading over Britain in 1996 showed a 47 percent reduction from the March average (Pearce, 1996). There was a 35 percent loss over Siberia in 1995, reductions of 10-15 percent over Europe as far south as Spain (Bojkov, 1995), and a loss of 5-18 percent in the U.S. (Komhyr et al., 1994). The greenhouse effect, which causes stratospheric cooling, may be contributing to ozone hole formation, and may also slow recovery even after ozone depleting substances start declining (Pearce, 1996; MacKenzie, 1995).
The results of the latest WMO/UNEP scientific assessment of ozone depletion, released 22 June 1998, confirm the effectiveness of the Montreal Protocol on Substances that Deplete the Ozone Layer (WMO/UNEP, 1998). A full recovery of the Earth's protective ozone shield could occur by the middle of next century if the Protocol is fully implemented. However, even though the Protocol is working well to reduce the use and release of ozone-depleting substances, the life of chemicals already released in the atmosphere will keep the depletion going for years to come.
The combined total abundance
of ozone-depleting compounds in the troposphere (the
The ozone layer in the stratosphere (about 12-45 km above the ground) shields the Earth's surface from the Sun's damaging ultraviolet (UV-B) rays. Exposure to increased UV-B radiation at the Earth's surface is known to result in skin cancer, and unpredictable damage to plants, algae, the food chain and the global ecosystem.
Among the atmospheric pollutants, there is new emphasis on tropospheric ozone, both because of its impact on the climate as a greenhouse gas, and because of the key chemical role that ozone plays in atmospheric chemical reactions, health impacts and environmental damage. Small particulates less than 10 microns in diameter are another recently recognized dangerous pollutant, causing early death among those suffering from lung and heart disease. This fine dust is produced by diesel exhausts, power stations and industry. The UK has estimated the safe level for these particles is exceeded in most cities 10 per cent of the time, causing 2,000 to 10,000 extra deaths a year (WHO, 1995; Martinson, 1996). Aerosols need to receive more attention, as they are now believed to play an important role in the climate change issue, but this has not been well assessed or quantified.
While acid rain has long been recognized as a problem in the industrial north, there is now evidence of the increasing danger of acid rain in South-East Asian countries (WMO). Emissions of sulphur dioxide have declined significantly in Europe and North America with reduced coal use and the application of emission clean-up techniques, and further progress is expected (EEA, 1995). This has reduced the sulphur contribution to acid rain, but surprisingly has also resulted in sulphur deficiencies in some agricultural soils, causing falling yields and the appearance of new diseases. (Schnug, Ewald, et al., 1995) A lack of sulphur may also contribute to increasing ozone pollution by reducing the ability of plants to oxidize it.
The same improvement has not been seen in nitrogen oxides and other pollutants from vehicles, where the reduction in emissions due to catalytic converters has been counterbalanced by a growing number of vehicles. Urban air quality in Europe has thus continued to deteriorate (EEA, 1995).
The worst pollution problems may appear in unexpected places, such as the Arctic, where high levels of toxins such as PCBs, DDT, toxaphene, hexachlorobenzene, chlordane, lindane, dieldrin, mercury and dioxin have been found. There appears to be a global process of distillation where pollutants evaporate in warmer areas, are transported by winds to the Arctic, and then condense out to become concentrated in Arctic food chains (Kidd et al., 1995).
Human activities have doubled the cycling of nitrogen in the earth's system. Four-fifths of nitric oxide emissions worldwide now come from human activities such as the combustion of fossil fuels, cultivation of certain crops, and especially the manufacture of nitrogen-rich fertilisers. The amount of industrially-fixed nitrogen applied to crops during the decade from 1980 to 1990 more than equals all that applied previously in human history (Pearce, 1997a). Nitrogen saturation causes eutrophication in coastal waters, urban smog, the death of trees, the leaching of nutrients from soils and the loss of fragile heaths. Symptoms of eutrophication (the process of over-fertilization whereby an aquatic or marine ecosystem may lose much of its natural capacity to support a wide variety of vegetation and wildlife) include toxic algal blooms, loss of fish habitat, hypoxia and anoxia, changes in species composition of plankton, elimination of entire food chains, and the death of fish and shellfish (Sea Technology, Dec 1996 & Jan 1997).
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