Another major flaw of climate change advocates is that they confuse correlation and causation. We admit that the global climate has been warming over the past three decades, and the concentration of carbon dioxide in the atmosphere has been surging over the same period. But they could only be called well-correlated, and do not necessarily imply carbon dioxide emissions have caused global warming. If the height of a tree planted in 1980 has also grown in the same period, can we conclude that its growth is caused by carbon dioxide emissions?

Other suspicious points remain to be clarified. The rise of carbon dioxide concentration is smooth, whereas the ascent of global temperature is circuitous and cyclic. Data show that carbon dioxide concentrations began rising steeply in the 1950s, while the upward inflection point of global temperatures was around the 1850s, according to the latest data by Mann and others. In the recent decade, carbon dioxide emissions have surged fourfold compared to the 1990s, whereas the global temperature did not increase between 1998 and 2008. If carbon dioxide is the culprit of climate change, how can we explain the disparities? We need further and deeper research into the details about climate change, rather than rush into a conclusion.

Nowadays, the view that human activities have caused climate change has dominated the scientific community, public opinion and political discussions. Why are we hardly listening to opposing voices?

In the scientific community, in fact, there are different views. Mainstream scientists who support the climate-change hypothesis, however, almost monopolize the discussion, and oppress the views of climate skeptics. Articles giving higher estimations for future temperatures are easier to publish, and the voices hyping the severity of climate change gain a wider audience. On the contrary, the works that doubt the authenticity of climate change are either rejected or neglected. The global scientific community behaves unfairly on this matter, and consequently it is not surprising that climate skeptics used "Climategate" prior to the Copenhagen conference as a counterstrike to the mainstream.

Climategate, however, was simply an event that stirred up trouble and should not be applauded. Non-mainstream scientists, despite all the unfairness they have suffered, should discuss with mainstream scientists, most of them reasonable and well-trained, on the scientific results and try to persuade public opinion. The scientific establishment as well as the general public should listen to the skeptics' voices, too.

The author is a professor of atmospheric science at Peking University.