The effects of global warming on the climate have tested the nerve of the city's fashion designers, who face big design challenges with unusual seasonal changes. According to data compiled by Ho Pui-yin, associate professor at the history department at Chinese University, records show that Hong Kong is gradually becoming warmer. The Observatory announced last year that the city's urban areas were heating up three times faster than the global average. In the past century, Hong Kong's temperature has risen by about 1.2 degrees, while the global average surface temperature has risen by 0.6 degrees. Seasonal changes were becoming more insignificant, especially winter, which was now usually warmer than in the previous century, Professor Ho said. Acclaimed local fashion designer William Tang Tat-chi complained global warming presented the industry with a major challenge in both design and marketing. 'Due to the warm weather, we have to design clothes for perennial uses, such as a tube top and T-shirt [to be worn throughout] the whole year,' he said. 'For winter, we design fur collars and cardigans to add on to the tube top and T-shirt - instead of making winter coats and sweaters. 'Winter used to be the most profitable for the trade because customers are more willing to pay for winter clothes ... so we are facing a big challenge from the weather. We also face a lot of constraints in design due to the limitations in choosing the material. 'The weather also makes it difficult for us to market our clothes, for example, winter clothes are unsold when the temperature remains high. So we are facing a big challenge from the weather.'