Previous studies investigated the Asian monsoon intensity in the late Miocene of southwestern China using the ratios of mean precipitation of the wettest and driest months to mean annual precipitation as indicators. However, the indices are based on two monthly means and not on mean values overall. Therefore, a new index is needed to accommodate the climatic parameters reconstructed based on paleoclimatic reconstructions.

Prof. Zhou Zhekun and his research team of Xishuangbanna Tropical Botanical Garden (XTBG) used Leaf Margin Analysis (LMA), Climate Leaf Analysis Multivariate Program (CLAMP) and Coexistence Approach (CA) to reconstruct the paleoclimate of the late Miocene Xianfeng flora.

The fossil site is situated in the Xianfeng Basin, 60 km north of Kunming, southwest China ; Yunnan (25°25′ N, 102°51′ E, asl 1900 m).

Their study was aimed: (1) to quantitatively reconstruct the paleoclimate of the Xianfeng flora, (2) to propose a monsoon index applicable to paleoclimatic reconstruction, and (3) to reconstruct the monsoon intensity in the late Miocene of Yunnan.

The results indicated that the Xianfeng flora experienced a monsoonal warm temperate climate. By comparing it with other neighboring late Miocene floras, the researchers concluded that Yunnan had a warmer, humid and seasonal climate. The precipitation seasonality was weaker and, based on their monsoon intensity index, a weaker winter monsoon was suggested.