First came global warming. When this was followed by some of the coldest winters in recent history it became "global change." Now we are told that "hail is one of the most extreme weather phenomena, causing great loss to agriculture every year in China (Han, 1999)."
Researchers Xie and Zhang had already found there was a "significant decreasing trend of hail frequency in most of China from the early 1980s based on 46 years of data during 1960-2005."
Therefore, they focused on hailstone size, noting that "changes in hail size are also an important aspect of hail climatology." The conclusion of the research is that there has been no increase. Data suggests a slight decline in frequency and a possible decrease in maximum hail diameter.
C02 Science gives the references for this research as Han, Hail hazard in Hebei province in the Journal of Catastrophe and Trends in Hail in China during 1960-2005 in Geophysical Research Letters.