Journey into China's 'climate cave' in Taihang mountains
China, the world's biggest polluter, is hosting a major UN conference on climate change this week.
The Chinese government says it wants to show the international community that it is taking the threat seriously.
Chinese scientists have been analysing new data that appears to show that man-made global warming could be having a significant effect on its weather.
The evidence was gathered in caves in the Taihang mountains on the edge of Beijing province.
Roger Harrabin reports.