Xu Lian

Plausible rice yield losses under future climate warming

Rice is the staple food for more than 50% of the worlds population1–3. Reliable prediction of changes in rice yield is thus central for maintaining global food security. This is an extraordinary challenge. Here, we compare the sensitivity of rice yield to temperature increase derived from field warming experiments and three modelling approaches: statistical models, local crop models and global gridded crop models. Field warming experiments produce a substantial rice yield loss under warming, with an average temperature sensitivity of −5.2 ± 1.4% K−1. Local crop models give a similar sensitivity (−6.3 ± 0.4% K−1), but statistical and global gridded crop models both suggest less negative impacts of warming on yields (−0.8 ± 0.3% and −2.4 ± 3.7% K−1, respectively). Using data from field warming experiments, we further propose a conditional probability approach to constrain the large range of global gridded crop model results for the future yield changes in response to warming by the end of the century (from −1.3% to −9.3% K−1). The constraint implies a more negative response to warming (−8.3 ± 1.4% K−1) and reduces the spread of the model ensemble by 33%. This yield reduction exceeds that estimated by the International Food Policy Research Institute assessment (−4.2 to −6.4% K−1) (ref. 4). Our study suggests that without CO2 fertilization, effective adaptation and genetic improvement, severe rice yield losses are plausible under intensive climate warming scenarios.

Spatiotemporal variations in the difference between satellite‐observed daily maximum land surface temperature and station‐based daily maximum near‐surface air temperature

There is an increasing demand to integrate land surface temperature (LST) into climate research due to its global coverage, which requires a comprehensive knowledge of its distinctive characteristics compared to near-surface air temperature (Tair). Using satellite observations and in situ station-based data sets, we conducted a global-scale assessment of the spatial and seasonal variations in the difference between daily maximum LST and daily maximum Tair (delta(T), LST - Tair) during 2003-2014. Spatially, LST is generally higher than Tair over arid and sparsely vegetated regions in the middle-low latitudes, but LST is lower than Tair in tropical rainforests due to strong evaporative cooling, and in the high-latitude regions due to snow-induced radiative cooling. Seasonally, delta(T) is negative in tropical regions throughout the year, while it displays a pronounced seasonality in both the midlatitudes and boreal regions. The seasonality in the midlatitudes is a result of the asynchronous responses of LST and Tair to the seasonal cycle of radiation and vegetation abundance, whereas in the boreal regions, seasonality is mainly caused by the change in snow cover. Our study identified substantial spatial heterogeneity and seasonality in delta(T), as well as its determinant environmental drivers, and thus provides a useful reference for monitoring near-surface air temperature changes using remote sensing, particularly in remote regions.

Extension of the growing season increases vegetation exposure to frost

While climate warming reduces the occurrence of frost events, the warming-induced lengthening of the growing season of plants in the Northern Hemisphere may actually induce more frequent frost days during the growing season (GSFDs, days with minimum temperature < 0 °C). Direct evidence of this hypothesis, however, is limited. Here we investigate the change in the number of GSFDs at latitudes greater than 30° N using remotely-sensed and in situ phenological records and three minimum temperature (Tmin) data sets from 1982 to 2012. While decreased GSFDs are found in northern Siberia, the Tibetan Plateau, and northwestern North America (mainly in autumn), ~43% of the hemisphere, especially in Europe, experienced a significant increase in GSFDs between 1982 and 2012 (mainly during spring). Overall, regions with larger increases in growing season length exhibit larger increases in GSFDs. Climate warming thus reduces the total number of frost days per year, but GSFDs nonetheless increase in many areas.Plant growing season increases under a warming climate, but it is not known whether this will alter plant exposure to frost days. Here Liu et al. investigate trends in the Northern Hemisphere over 30 years and find increased exposure to frost days in regions that have longer growing seasons.

Impact of Earth Greening on the Terrestrial Water Cycle

AbstractLeaf area index (LAI) is increasing throughout the globe, implying the Earth greening. Global modelling studies support this contention, yet satellite observations and model simulations have never been directly compared. Here, for the first time, we used a coupled land-climate model to quantify the potential impact of the satellite-observed Earth greening over the past 30 years on the terrestrial water cycle. The global LAI enhancement by 8% between the early 1980s and the early 2010s is modelled to have caused increases of 12.0 ±2.4 mm yr-1 in evapotranspiration and 12.1 ±2.7 mm yr-1 in precipitation — about 55 ±25% and 28 ±6% of the observed increases in land evapotranspiration and precipitation, respectively. In wet regions, the greening did not significantly decrease runoff and soil moisture because it intensified moisture recycling through a coincident increase of evapotranspiration and precipitation. But in dry regions including Sahel, West Asia, northern India, western United States and the...

Responses of land evapotranspiration to Earth's greening in CMIP5 Earth System Models

Satellite-observed Earths greening has been reproduced by the latest generation of Earth System Models (ESMs) participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Land evapotranspiration (ET) is expected to rise with increasing leaf area index (LAI, Earths greening). The responses of ET play a key role in the land–climate interaction, but they have not been evaluated previously. Here, we assessed the responses of ET to Earths greening in these CMIP5 ESMs. We verified a significant and positive response of ET to the modeled greening in each model. However, the responses were not comparable across the ESMs because of an inherent bias in the sensitivity of ET to LAI

Partitioning global land evapotranspiration using CMIP5 models constrained by observations

(\partial {\rm{E}}{\rm{T}}/\partial {\rm{L}}{\rm{A}}{\rm{I}})

Regional patterns of future runoff changes from Earth system models constrained by observation

in the models:

Divergent hydrological response to large-scale afforestation and vegetation greening in China

\partial {\rm{E}}{\rm{T}}/\partial {\rm{L}}{\rm{A}}{\rm{I}}

Comment on “Satellites reveal contrasting responses of regional climate to the widespread greening of Earth”

is precisely and inversely proportional to the trend of LAI

Seasonal Responses of Terrestrial Carbon Cycle to Climate Variations in CMIP5 Models: Evaluation and Projection

(\partial {\rm{L}}{\rm{A}}{\rm{I}}/\partial t)