The Scorching Summer of 2015
- Friday, 25th September 2015
The U.S. National Oceanic and Atmospheric Administration recently announced that the globally averaged temperature over land and ocean surfaces in summer (June to August) 2015 was the highest ever recorded for the globe since 1880.
Hong Kong also experienced the hottest summer ever since records began in 1884 with the mean temperature for June to August 2015 reaching 29.4 degrees, breaking the previous record of 29.3 degrees set not so long ago last year.
June 2015 was actually the hottest June on record (Table 1). Under the subsidence effect associated with Typhoon Soudelor, the temperature at the Hong Kong Observatory soared to a record-breaking 36.3 degrees on 8 August 2015, beating the previous extreme of 36.1 degrees set in 1990. More details on the record-breaking temperatures this summer are summarized in Table 2.
In fact, under the combined influence of global warming and urbanization development, there is a very significant long-term rising trend in the summer mean temperatures in Hong Kong (Figure 1). Record-breaking temperatures are evidently becoming more frequent, with four of the six hottest summers occurring within the past seven years (Table 3). Looking forward, if we fail to reduce greenhouse gas emission as soon as possible, the latest climate projections suggest that under a high emission scenario, the mean temperature in Hong Kong is expected to rise 1.5 - 3.0oC by the mid-21st century (2051-2060) as compared to the 1986-2005 average. This implies that very hot days, hot nights and extreme temperature records in future summers would only keep increasing, bringing negative impacts to our living conditions, especially for the underprivileged who have to stay in congested and poorly ventilated environment. The very hot conditions will also mean enhanced air-conditioning demand and hence more energy consumption. This will create a vicious negative feedback cycle with a profound implication of adverse social and economic consequences in the long run.
Figure 1 - Long Term Trend of Summer Mean Temperature (June - August) recorded at the Hong Kong Observatory
K W Li and K M Leung
 NOAA Global Analysis - August 2015
 Record-breaking high temperature
 Hong Kong temperature projections