China is experiencing a well-documented, widespread warming. The glaciers on the Tibetan Plateau are retreating rapidly, and permafrost is melting. This rate has accelerated in the early 21st century under the impact of an intensified South Asia Monsoon, which is likely a consequence of global warming.
Yao Tandong and others trace the glacial retreat in China to the termination of the Little Ice Age, around the beginning of the 20th century. Since then, the glacial retreat can be divided into several stages. The first half of the 20th century was characterized by shifting from glacial advances to retreats. Between the 1950s and the 1960s, the glaciers began extensive retreat, with over half of the studied glaciers retreating, about 30 percent advancing, and the others stable. In a short period from the late 1960s to the late 1970s, advancing glaciers increased again and the percentage of retreating glaciers decreased to less than half. Starting in the 1980s, glacier retreat intensified again, with 90 percent of the studied glaciers retreating. Since the 1990s, glacial retreat has been accelerating, with 95 percent of the studied glaciers now retreating.
The magnitude of glacial retreat is less on the northern Tibetan Plateau, and more at the margins; the greatest retreats are on the southeast plateau. The rate of glacial retreat reached 213 ft. (65 m.) per year on the southeast plateau, where the South Asia Monsoon prevails. The smallest glacial retreat appears on the central plateau, where a continental climate dominates.
Monsoons and the Westerlies affect the dominant patterns of glacial retreat on the Tibetan Plateau. The monsoon water vapor flows through the lower reaches of the Brahmaputra River valley toward the interior of the plateau, which results in the development of the largest glaciers. With global warming, the Southeast Asia Monsoon is intensifying, which causes more precipitation on the southeastern plateau. The increased precipitation there comes mostly as rainfall, as opposed to the situation in the mountains influenced by the Westerlies, where increased precipitation on high elevation glaciers falls mostly as snow. Trends showed strong increases for spring and winter precipitation from 1961 to 2001.
Over the last decade, many lakes in highly glaciated regions have expanded. Yao Tandong and others assessed size changes of lakes greater than 3.7 sq.
mi. (10 sq. km.) and discovered that over 70 percent of the lakes evaluated expanded by at least 12 percent, since the 1990s. Glaciological observations in the region suggest that intensified glacial melting in response to the current warming is the principal driver, not precipitation patterns over the plateau.
Lake expansion will most likely modify the hydro-logic cycle over the Tibetan Plateau. Grassland destruction and resultant reduction of livestock grazing is now occurring near Lhasa. (Higher CO2 concentrations also favor woody plants over grasslands.) Furthermore, the potential for glacial lake outburst flooding is also increasing, which could cause serious damage in south Asian countries such as India, Nepal, and Bhutan.
The southern limits of China's permafrost appear to be moving northward at over .93 mi. (1.5 km.) per year. The area of permafrost is expected to decline by 30-50 percent during this century. Permafrost collapse tends to cause slumping of the soil surface and flooding, followed by a complete change in vegetation, soil structure, and many other important aspects of these ecosystems. Melting permafrost causes concern, because frozen ground stores huge quantities of carbon as methane and CO2.
Recent studies show that initial flooding caused by melting boosts plant productivity, sequestering more carbon from the atmosphere in plant biomass. Hence, permafrost degradation may initially increase soil carbon sequestration, rather than release large amounts of carbon into the atmosphere, as originally predicted. But over time, the greenhouse effect of high methane emissions will outweigh the reduction of carbon in the atmosphere.
Chinese scientists conclude that human activities have accelerated the desertification process and have driven the north China deserts southward by approximately 186 mi. (300 km.) over the past 3,000 years. A growing population, intensive agricultural activities, excessive tree-cutting, and frequent warfare have damaged the natural vegetation, caused soil erosion, and intensified desertification. Reforestation projects and greater rainfall from changes in the East Asia Monsoon patterns currently affecting the semi-arid to arid areas in this region are likely to help prevent and reverse desertification. However, water shortages will persist, due to lack of glacier storage and the current heavy mining of ground water.
Most recently, both the International Energy Agency and the Netherlands Assessment Agency say that China became the world's leading source of greenhouse gas emissions in 2007. According to the World Bank, Chinese industry uses 4-10 times more water per unit of production than the average in industrialized nations. China ratified the Kyoto Protocol in 2002, but as a developing nation was not held to specific emissions targets. China's emissions of sulfur dioxide and particulates that act contrary to greenhouse gases (decreasing radiative heating in the lower atmosphere) are increasing even faster than China's economic growth. Their control may exacerbate the warming.
The China Daily recently reported that over 400 sq. mi. (644 sq. km.) of land in southern China would be flooded by 2050 as sea levels rise due to global warming. The Pearl River Delta area, a leading manufacturing hub, will be hard hit by climate change in the coming decades. The cities of Guangzhou, Zhuhai, and Foshan are expected to be the worst hit as sea levels rise by at least 11.8 in. (30 cm.) by 2050. Climate change will thus likely depress economic development of this province, which is currently one of the biggest consumers of energy and producers of greenhouse gases.
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