HKU Bulletin September 2007 (Vol. 9 No. 1)

12 13 A Quest for the Best Climate Projection Tools D r Chen Ji, an Assistant Professor in the Department of Civil Engineering, is using a regional climate model to study climate projection. Echoing a widely-held belief he said, “It’s difficult to predict climate change exactly. The Hong Kong Observatory’s projection is that there will be about a 3.5 degree increase in temperature over the next one hundred years in Hong Kong. But verifying this change and understanding the uncertainty of the projection require a lot of research.” Currently, the basic tool for studying, and projecting, climate change is the global climate model (GCM). It has the ability to consider different scenarios, including greenhouse gas emissions. But the problem, according to Chen, is that the current capability of the climate model may not exactly predict abrupt climate change features. “There are a lot scientific issues involved in climate projection. We know that climate change, especially after the 1980s, has been quite rapid. Some of this is due to land cover changes, some to urbanization and greenhouse gas emissions.” But, although global climate models are important tools for studying climate change, they generally cannot give details on regional climate. The Global Spectral Model (GSM) is used to simulate global climate. Chen used the Regional Spectral Model (RSM) to downscale it for specific regions, like Southern China. He then used climate projection data from the European Centre Hamburg Model (ECHAM) to project the temperatures in Hong Kong in the months of January and June between 2010- 2014. ECHAM’s data for January and June 1971 to 2000 was used to compare the pattern. “After downscaling and taking the 30-year climate average for the region I looked at the domains from different spatial resolutions – 15 km for Hong Kong and 30 km, which covers the entire Pearl River Basin (PRB). “In January for the PRB domain, the average temperature for the period was 14.53 degrees. But the ECHAM projection for 2010-2014, is above 17 degrees. “If we look at June, and the smaller domain of 15 km for Hong Kong, the average increase in temperature is not so significant – only about point five degree increase. “The temperature increase projected by the global model of 3.5 degrees for the next one hundred years generally combines everything together. But by using the regional model we can see that the significant increase is in January (or winter, dry season). In June (or summer, wet season) maybe it’s not so significant.” Chen said he was confident about the results because his previous research showed a similar pattern. “So when I saw these results I thought they were very interesting and also quite reasonable. “The observation data, station recorded data, for winter months in Hong Kong between 1980 and 2000 reflects this. So if this trend continues maybe we will end up with a less dramatic change in the seasons. “There are still many challenges with downscaling but I think the way we are working now is very solid, we can move step by step towards understanding climate change. It’s very important for human beings especially in terms of understanding extreme weather. To understand floods and droughts we have to understand climate and we have to understand atmosphere. And the way we are working can be useful for understanding water sources security for the region.” What his research has shown is the necessity of downscaling global models to study regional and local climate change. “Although downscaling is a challenge, the simulation domain and spatial resolution are critical factors for evaluating projections and studying climate change.” The Implications of Living in a Warmer World Although research on the regional impact of climate change has experienced a low priority in Hong Kong, the University has identified it as a strategic research theme. Here we offer a glimpse of some of the research being conducted at HKU in this increasingly-important area. COVER STORY