Multiple large-scale wildfires have been raging across California since October this year.

The largest of the blazes, the Thomas Fire has burned over 280,000 acres in southern California, destroying more than 1,000 structures in its path and forcing the evacuation of more than 200,000 people. Two deaths linked to the fire which broke out in early December have been reported. The U.S. Forest Service said that the Thomas Fire is the largest blaze in modern California history with economic cost amounting to more than US$10 billion.

Research found that climate change is increasing the frequency and size of California wildfires. Dr Chun Kwok-pan, Assistant Professor of the Department of Geography, explained that in terms of geographical location, it is typical for the East Pacific to be drier than the West Pacific because of the general atmospheric and oceanic circulations. Coastal California has what is known as the Mediterranean climate, with mild, wet winters and hot, dry summers. However, California has been dry for more than half a decade (starting around 2012) due to climate change. During an El Niño episode, California is generally expected to be wetter. Yet, the last El Niño episode did not bring an end to California's drought.

In addition, the seasonal Santa Ana winds, which are strong, extremely dry downslope winds causing bone-dry conditions in California, has set the stage for massive wildfires. What’s more, the winds increase the amount of dried vegetation which "fuels" the fire and it also helps to fan the flames, finally leading to uncontrolled blazes.

Dr Chun said there are several causes for wildfires. Though geographical location and climate may provide a favourable condition to wildfires, most blazes are caused by humans. "Volcano eruption, lighting and heat wave are the natural causes of fires. However, acts by humans, whether careless or deliberate, are the leading cause of wildfires both overseas and in Hong Kong. In order to enhance public awareness on wildfire prevention, we should work on educating the public." He added, controlled burn can be useful for reducing vegetation buildup and lowering the likelihood of serious hotter fires.

There are also a number of wildfires in Hong Kong every year. Dr Chun revealed that increasing temperatures may cause frequent blazes in our countryside. However, Hong Kong is likely to be wetter so the local climate is not favourable to massive and destructive wildfires. That said, more development and tourists inside country parks may lead to more human-caused fires.