Himalayan glaciers experienced significant mass loss during later phases of little ice age.

To date, there is a gap in the data about the state and mass balance of glaciers in the climate-sensitive subtropical regions during the Little Ice Age (LIA). Here, based on an unprecedented tree-ring sampling coverage, we present the longest reconstructed mass balance record for the Western Himalayan glaciers, dating to 1615. Our results confirm that the later phase of LIA was substantially briefer and weaker in the Himalaya than in the Arctic and subarctic regions. Furthermore, analysis of the time-series of the mass-balance against other time-series shows clear evidence of the existence of (i) a significant glacial decay and a significantly weaker magnitude of glaciation during the latter half of the LIA; (ii) a weak regional mass balance dependence on either the El Niño-Southern Oscillation (ENSO) or the Total Solar Irradiance (TSI) taken in isolation, but a considerable combined influence of both of them during the LIA; and (iii) in addition to anthropogenic climate change, the strong effect from the increased yearly concurrence of extremely high TSI with El Niño over the past five decades, resulting in severe glacial mass loss. The generated mass balance time-series can serve as a source of reliable reconstructed data to the scientific community.

Reconstructing atmospheric CO2 during the Plio-Pleistocene transition by fossil Typha.

The Earth has undergone a significant climate switch from greenhouse to icehouse during the Plio-Pleistocene transition (PPT) around 2.7-2.4 million years ago (Ma), marked by the intensification of the Northern Hemisphere glaciation (NHG) ~2.7 Ma. Evidence based on oceanic CO2 [(CO2)aq], supposed to be in close equilibrium with the atmospheric CO2 [(CO2)atm], suggests that the CO2 decline might drive such climate cooling. However, the rarity of direct evidence from [CO2]atm during the interval prevents determination of the atmospheric CO2 level and further assessment on the impact of its fluctuation. Here, we reconstruct the [CO2]atm level during 2.77-2.52 Ma based on a new developed proxy of stomatal index on Typha orientalis leaves from Shanxi, North China, and depict the first [CO2]atm curve over the past 5 Ma by using stomata-based [CO2]atm data. Comparisons of the terrestrial-based [CO2]atm and the existed marine-based [CO2]aq curves show a similar general trend but with different intensity of fluctuations. Our data reveal that the high peak of [CO2]atm occurred at 2.77-2.52 Ma with a lower [CO2]aq background. The subsequent sharp fall in [CO2]atm level might be responsible for the intensification of the NHG based on their general temporal synchronism. These findings shed a significant light for our understanding toward the [CO2]atm changes and its ecological impact since 5 Ma.