Global warming has become a household term, but the widespread chill has raised doubts among the public about whether Earth is in the grip of global cooling.

Ding Yihui, deputy director-general of Climate Change Experts Committee and executive director of the scientific committee of World Climate Research Program, said the temporary period of low temperatures does not indicate that global warming has slowed.

The term global warming means the temperature of Earth is generally rising, but it still has relatively cold and warm periods, Ding told People's Daily.

According to the second National Assessment Report on Climate Change, released last year, land surface temperatures in China increased by 1.38 C from 1951 to 2009.

Ding said global warming is not only driving up the temperature, but also causing frequent extreme weather events such as drought and extreme cold.

Aside from global warming, surface cooling of oceans and weaker sun can cause temperatures to drop, he added.

In January, about 42 meteorological monitoring stations saw record-breaking low temperatures.

In Shenyang, Liaoning province, the unusual cold has driven up the number of patients with colds and respiratory complaints by at least 30 percent in the past week, said Wang Lijie, a doctor at Shengjing Hospital.

Li Danyang, a 30-year-old Shenyang resident, was on a drip on Sunday after contracting a severe cold.

"About 30 percent of my co-workers have gotten colds," she said.

Since Dec 30, the average temperature in Liaoning was -11 C , about 1.4 C lower than normal during the same period in the past 20 years, according to the Liaoning meteorological bureau.

Beijing released its first cold alert on Sunday, warning of strong winds and a sudden temperature drop of 8 C within two days.

Fog and snow brought by the cold caused the closure of 11 highways across the country on Monday, according to the Ministry of Transport.

Tianhe airport in Wuhan, Hebei province, delayed 47 flights on Sunday because of heavy fog, and more than 3,000 passengers were stranded at the airport, according to the airport.

On Friday, Hukou Waterfall in Shanxi province froze after the temperature remained -10 C for days.