In urban areas, change even more marked
The winter season became shorter by an average of ten days in areas across the nation in the 31 years leading up to 2004, largely due to global warming, researchers said. The phenomenon was particularly evident in urban areas. According to climatological research led by Choi Gwang-yong of Rutgers University in the U.S. and Kwon Won-tae of the National Meteorological Administration of Korea, spring started an average six days earlier across the country between 1973 and 2004, while winter started four days later than usual. This means that winter has become about ten days shorter on average. In order to determine the "beginning" and "end" of seasons, researchers used a Summed Daily Temperature (SDT) that denotes the average of the combined values of daily Minimum, Mean, and Maximum temperatures over a period of seven days. If the SDT dropped below 15 degrees Celsius, it denoted the start of winter. Summer began if the SDT went over 60 degrees Celsius. The research also found that Seoul’s winter became 12 days shorter during the 1973-2004 time period, and the nation’s other large urban areas showed similar figures. The season became 17 days shorter in Busan, Daegu 14 days, and Jeju city 24 days. Areas which have urbanized at a slightly slower rate showed less shortening of their winters: Yangpyeong, Youngcheon, Seongsanpo, and Geoje saw their winters shorten on average by three, seven, 10, and 11 days, respectively."Based on the comparison of climates in urban and rural areas, we found that urbanization accounted for around 30 percent of the total average climate change," a researcher who participated in the study said. Urbanization also affected summer, as well. The season became an average three days longer than usual across the nation during the 1973-2004 time period. But in areas where urbanization took place at a faster pace than others, such as Ulsan and Pohang in the Gyeongsang provinces, the summer season became 10 days longer. For Jeju city and Seoguipo, summer became six and eight days longer, respectively. On the contrary, Haenam and Goheung, rural areas off the southern coast, saw an average six-day shorter summer. The research attributed the polarization in temperatures between urban and rural areas to concrete-walled buildings that absorb heat radiation from the sun. In addition, the destruction of forests and other green areas around cities has contributed to heat waves during the summer season, the researchers said. "Urbanization, not just greenhouse gas emissions, is no less a critical factor in affecting climate. So the use of concrete in urban development should be comprehensively evaluated," a researcher on the project said. Please direct questions or comments to [englishhani@hani.co.kr]
