RESEARCH

The Tibetan Plateau is of crucial importance for the global hydrological, energy and element cycles and represents one of the most vulnerable geo-ecosystems on Earth. The 6^th IPCC Assessment Report highlighted the TP as one of the most sensitive areas to global climate change already observed and was predicted to experience an increase in heavy precipitation events and hot extremes (AR6 IPCC, 2021). Precipitation has risen by 12% since 1960, and temperatures have soared by 0.4°C per decade - twice the global average (Qiu, 2014). Temperature rise has led to a retreat rate of glaciers on the TP between 1970 and 2000 of up to 0.57% yr^-1 (Yao et al., 2012). Likewise, the areal extent of permafrost in China has been reduced by about 18.6% during the last 30 years (Cheng and Jin, 2013). A significant wetting trend since the early 1980s has been observed (Fang et al., 2015) and green-up dates in the TP have continuously advanced since 1982 (Zhang et al., 2013).

These observed and predicted climate changes will have a pronounced impact on geo-ecosystems on the TP and will significantly alter the water supply of a major part of Asia, home to almost two thirds of the world's population (Messerli, 2012). Changes in the hydrological cycle will be accompanied by significant changes in sediment and carbon (C) fluxes with potential severe consequences for terrestrial and aquatic biota. It is thus of utmost importance to assess to what extent geo-ecosystems on the TP are threatened by rapidly changing environmental conditions.

The scientific goals of TransTiP are to

1. quantify rates of sediment movement and transport,
2. identify the impact of land-use on soil carbon fluxes,
3. determine water balances and climate-change effects on geo-ecosystems, and
4. understand, how societies interact with these changes.

For this reason we identified the following overarching research question:

How will Earth surface fluxes change with the projected future climate change and which consequences are to be expected for water ressources, biodiversity and species composition and distribution?

Based on that, we developed three more detailed questions:

1. How, how fast and to what spatial extent do Earth surface fluxes, for example soil erosion and sediment transport, C fluxes and river flow, respond to climate change?
2. What are the seasonal and inter-annual variabilities as well as the magnitudes and rates of current Earth surface fluxes?
3. How did these Earth surface fluxes vary on decadal to centennial time scales, especially during the past 2000 years?
4. How has environmental change affected abiotic and biotic components of geo-ecosystems?
5. How have local communities responded to climate changes in the past and are responding at present day?