(8) Air Pollution

 Air Pollution Causes More than 6 Million Deaths Worldwide

Air quality to suffer with global warming

Air Quality and Climate Change

Air Pollution - Comes From Many Sources


What Are Some Possible Effects of a Warmer Atmosphere?

CONCEPT 15-4 Some areas will benefit from a warmer climate and others will suffer from melting ice, rising sea levels, more extreme weather events, increased drought and floods, and shifts in locations of wildlife habitats and agricultural areas.

 Global Warming Can Have Harmful and Beneficial Effects

A warmer global climate could have a number of harmful and beneficial effects for humans, other species, and ecosystems, depending mostly on where they are located and on how rapidly the temperature changes. Some areas will benefit because of less severe winters, more precipitation in some dry areas, less precipitation in wet areas, and increased food production.

Other areas will suffer harm from excessive heat, drought, and decreased food production (Concept 15-4).

According to the IPCC, the world’s poor, who are least responsible for global warming, and wild species in the tropics (especially Africa and parts of Asia) will suffer the most harm.

According to a study by Agiuo Dai and his colleagues, between 1979 and 2002, the area of the earth’s land (excluding Antarctica) experiencing severe drought tripled and affected an area the size of Asia, mostly because of global warming. This browning of the land is expected to increase sharply and decrease water supplies and biodiversity in many areas. According to the 2007 IPCC report, hundreds of millions of people would suffer from water scarcity, with just a small rise in temperatures. However, if the average temperature rose by more that 4 C°(7 F°), 1.1 to 3.2 billion people might suffer from water shortages. According to the IPCC, areas projected to have increased drought by 2080–2099 include the western United States, the Mediterranean basin, southern Africa, southern and eastern Australia, and northeastern Brazil. The same report projected more days of heavy rain with increased flooding in areas of Canada, most of Europe, and the northern parts of the United States.


Predicting the effects of global warming in different parts of the world

Ice and Snow Are Melting in the Arctic

Environmental scientists are alarmed by recent news that parts of the Arctic are warming two to three times faster than the rest of the earth. Over the past 30 years, snow cover in the Arctic has declined by about 10%, mountain glaciers are melting and retreating, and permafrost is beginning to thaw in some areas. The melting of such reflective ice and snow exposes much darker land and water, which absorb more solar energy, and accelerates global warming.

In 2006, the U.S. National Oceanic and Atmospheric Administration issued a State of the Arctic report in which researchers predicted Arctic summers without floating sea ice by 2040 and perhaps much earlier. Because sea ice floats, it does not contribute to a rising sea level when it melts. However, open water reflects much less sunlight and absorbs more heat than do reflective ice or snow. Hence, floating ice turning to water during the Arctic summer will accelerate the warming of the lower atmosphere. The Arctic’s contribution to a rising sea level will come from land-based ice and snow that melts and runs into the sea. This is especially true in Greenland, a large mountainous island, which is covered almost completely by glaciers that are up to 3.2 kilometers (2 miles) deep. These glaciers contain about 10% of the world’s freshwater-enough water to raise the global sea level by as much as 7 meters (23 feet) if the glaciers all melt. This would flood many coastal cities and large areas of farmland.

Until recently scientific models of Greenland assumed that this huge solid block of ice would take thousands of years to melt. But recent satellite measurements made by scientists at the University of Kansas Jet Propulsion Laboratory show that Greenland’s net loss of ice more than doubled between 1996 and 2006 and is not being replaced by increased snowfall. Even partial melting will accelerate the projected average sea level rise during this century. Some climate scientists, such as James Hansen (Core Case Study), warn that once Greenland’s glacier starts to disintegrate they could reach a tipping point beyond which the breakup would occur very rapidly.

Mountaintop glaciers are affected by two climatic factors: snowfall that adds to their mass during the winter and warm temperatures that spur melting during the summer. As temperatures go up, melting exceeds snowfall and the glaciers begin receding. During the last 25 years, many of the world’s mountaintop glaciers have been melting and shrinking at accelerating rates. For example, climate models predict that by 2070, Glacier National Park in the United States will have no glaciers. In 2007, scientists projected that at their current rate of melting most glaciers will disappear from Europe’s Alps somewhere between 2037 and 2059. As mountain glaciers disappear, at least 300 million people in countries such as Bolivia, Peru, Ecuador, and India, who rely on meltwater from such glaciers could face severe water shortages.

Sea Levels Are Rising

According to the 2007 IPCC report, the world’s average sea level is very likely (90-99% certainty) to rise 8–59 centimeters (0.6–1.9 feet) during this century-about two-thirds of it from the expansion of water as it warms, and the other third from the melting of land-based ice.

However, larger rises in sea levels of up to 1 meter (39 inches) by 2100 cannot be ruled out if glaciers in Greenland reach a tipping point and continue melting at their current or higher rates as the atmosphere warms.

According to the IPCC, the projected increases in sea levels during this century could:

  •          Threaten at least one third of the world’s coastal estuaries, wetlands, and coral reefs,
  •          Disrupt many of the world’s coastal fisheries,
  •        Flood low-lying barrier islands and cause gently sloping coastlines (especially on the U.S. East Coast) to erode and retreat inland,
  •          Flood agricultural lowlands and deltas in coastal areas where much of the world’s rice is grown,
  •         Contaminate freshwater coastal aquifers with saltwater,
  •         Submerge some low-lying islands in the Pacific Ocean, the Caribbean Sea, and the Indian Ocean, and
  •      Flood coastal areas, including some of the world’s largest cities, and displace at least 100 million people, especially in China, India, Bangladesh, Vietnam, Indonesia, and Japan.

Permafrost Is Melting: Another Dangerous Scenario

Global warming could be accelerated by an increased release of methane (a greenhouse gas 23 times more potent, per volume, than carbon dioxide) from four major sources: natural decay in swamps and other freshwater wetlands, decay from garbage in landfills, melting permafrost in soils and lake beds, and ice-like compounds called methane hydrates trapped beneath arctic permafrost and on the deep ocean floor.

The amount of carbon locked up as methane in permafrost soils is 50–60 times the amount emitted as car bon dioxide from burning fossil fuels each year. Significant amounts of methane and carbon dioxide would be released into the atmosphere if the permafrost in arctic areas melts. This is already happening on a small scale in parts of North America and Asia, and as the earth gets warmer, it could accelerate. According to the 2004 Arctic Climate Impact Assessment, 10–20% of the Arctic’s current permafrost might thaw during this century and decrease the area of Arctic tundra.

A warmer atmosphere could melt more permafrost and increase emissions of CH4 and CO2. This would cause more warming and more permafrost melting, which would cause still more warming.

Ocean Currents Are Changing but the Threat Is Unknown

Ocean currents, which on the surface and deep down are connected, act like a gigantic conveyor belt, moving CO2 and heat to and from the deep sea, and transferring hot and cold water between the tropics and the poles.

Scientists are concerned that melting of land-based glaciers from global warming (especially in Greenland) and increased rain in the North Atlantic could add enough freshwater to the ocean in the arctic area to slow or disrupt this conveyor belt. Reaching this tipping point would drastically alter the climates of northern Europe, northeastern North America, and probably Japan. The exact nature and likelihood of this possible threat is still unknown, but most climate scientists do not see it as a major threat in the near future.

Extreme Weather Will Increase in Some Areas

Global warming is projected to alter the hydrologic cycle and shift patterns of precipitation, causing some areas to get more water and other areas to get less. This could shift the locations of areas where crops could be grown and where people could live (Concept 15-4).

According to the IPCC, global warming will increase the incidence of extreme weather such as prolonged, intense heat waves and droughts, which can kill large numbers of people and expand deserts. At the same time, other areas will experience increased flooding from heavy and prolonged precipitation.

Researchers have not been able to establish that global warming will increase the frequency of tropical hurricanes and typhoons. But a 2005 statistical analysis by MIT climatologist Kerry Emmanuel and six other peer-reviewed studies published in 2006 indicated that global warming, on average, could increase the size and strength of such storms in the Atlantic by warming the ocean’s surface water.

On the other hand, some researchers blame the recently increased ferocity of tropical Atlantic hurricanes on natural climate cycles. More research is needed to evaluate these opposing hypotheses. More research is needed to evaluate the scientific controversy over the effects of global warming on hurricane frequency and intensity.

Maldives in the Indian Ocean, even a small rise in sea level could spell disaster for most of its 295,000 people. About 80% of the 1,192 small islands making up this country lie less than 1 meter (39 inches) above sea level. Rising sea levels and higher storm surges during this century could flood most of these islands and their coral reefs.


Global Warming Is a Major Threat to Biodiversity

According to the 2007 IPCC report, changes in climate are now affecting physical and biological systems on every continent. A warmer climate could expand ranges and populations of some plant and animal species that can adapt to warmer climates, including certain weeds, insect pests such as fire ants and ticks, and disease-carrying organisms.

Changes in the structure and location of wildlife habitats could cause the premature extinction of as many as 1 million species during this century (Concept 15-4). One of the first mammal species to go may be the polar bear (see front cover), as arctic sea ice, on which the bears hunt seals and other marine mammals, diminishes. By 2050, polar bears may be found mostly in zoos.

The ecosystems most likely to suffer disruption and species loss are coral reefs, polar seas, coastal wetlands, arctic and alpine tundra, and high-elevation mountaintops.

Forest fires may increase in some areas. Shifts in regional climate would also threaten many parks, wildlife reserves, wilderness areas, and wetlands-wiping out more biodiversity. In other words, slowing global warming would help sustain the earth’s biodiversity.

Global Warming Will Change Locations of Areas Where Crops Can Be Grown

Farming depends on a stable climate, probably more than any other human endeavor. Global warming will upset this stability by shifting climates and speeding up the hydrologic cycle (Concept 15-4).

Agricultural productivity may increase in some areas and decrease in others. For example, models project that warmer temperatures and increased precipitation at northern latitudes may lead to a northward shift of some agricultural production from the breadbasket of the midwestern United States to midwestern Canada.

But overall food production could decrease because soils in midwestern Canada are generally less fertile than those to the south. Crop production could also increase in Russia and Ukraine. In 2007, a panel of scientists from six Chinese government agencies warned that rising temperatures during the second half of this century could slash the country’s grain production by over a third, melt glaciers, increase pressure on its already scarce water resources in many areas, change its forest industry, and cause flooding in coastal areas that include 21 of its 33 largest cities.

Models predict a decline in agricultural productivity in tropical and subtropical regions, especially in Southeast Asia and Central America, where many of the world’s poorest people live. In addition, flooding of river deltas due to rising sea levels could reduce crop and fish production in these productive agricultural lands and coastal aquaculture ponds. According to the IPCC, for a time, food will be plentiful because of the longer growing season in northern regions. But by 2050, 200–600 million people could face starvation from decreased food production.

Global Warming Could Threaten the Health of Many People

According to the IPCC and a 2006 study by U.S National Center for Atmospheric Research, heat waves in some areas will be more frequent and prolonged, increasing death and illness, especially among older people, those with poor health, and the urban poor who cannot afford air conditioning. During the summer of 2003 (based on a detailed analysis in 2006 by Earth Policy Institute), such a heat wave killed about 52,000 people in Europe-almost two-thirds of them in Italy and France.

On the other hand, in a warmer world fewer people will die from cold weather. But a 2007 study by Mercedes Medin-Ramon and his colleagues suggested that increased heat-related deaths would be greater than the drop in cold-related deaths.

Incidences of tropical infectious diseases such as dengue fever and malaria are likely to increase if mosquitoes that carry them spread to temperate and higher elevation areas that are getting warmer. A 2006 study by Nils Stenseth at the University of Oslo found that the bacterium that causes bubonic plague, which killed more than 20 million people in the Middle Ages, could spread if the flea populations increase as temperatures rise. In addition, hunger and malnutrition will increase in areas where agricultural production drops.

A 2005 WHO study estimated that each year, climate change already prematurely kills more than 160,000 people-an average of 438 people a day-and that this number could double by 2030. In addition, the WHO estimates that climate change causes 5 million sicknesses each year. By the end of this century, the annual death toll from global warming could be in the millions.

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