CORDIS OpenAire University of Groningen Research Portal CORE (RIOXX-UK Aggregator) Research@WUR Sygma Bielefeld Academic Search Engine (BASE) UnpayWall HAL-INSU Crossref Microsoft Academic Graph Europe PubMed Central HAL-CEA European Union Open Data Portal https://centaur.reading.ac.uk/78233/1/manuscript_WUE_v20_maintext.pdf http://www.nature.com/articles/s41561-018-0212-7.pdf https://doi.org/10.1038/s41561-018-0212-7 Nature Geoscience Open Access 2018-08-22 2020-10-23 Severe droughts in the Northern Hemisphere cause widespread decline of agricultural yield, reduction of forest carbon uptake, and increased CO2 growth rates in the atmosphere. Plants respond to droughts by partially closing their stomata to limit their evaporative water loss, at the expense of carbon uptake by photosynthesis. This trade-off maximizes their water-use efficiency, as measured for many individual plants under laboratory conditions and field experiments. Here we analyze the 13C/12C stable isotope ratio in atmospheric CO2 (reported as δ13C) to provide new observational evidence of the impact of droughts on the water-use efficiency across areas of millions of km2 and spanning one decade of recent climate variability. We find strong and spatially coherent increases in water-use efficiency along with widespread reductions of net carbon uptake over the Northern Hemisphere during severe droughts that affected Europe, Russia, and the United States in 2001-2011. The impact of those droughts on water-use efficiency and carbon uptake by vegetation is substantially larger than simulated by the land-surface schemes of six state-of-the-art climate models. This suggests that drought induced carbon-climate feedbacks may be too small in these models and improvements to their vegetation dynamics using stable isotope observations can help to improve their drought response. FLUXES 330 GRASSLAND MODELS 0207 environmental engineering 02 engineering and technology CARBON-ISOTOPE DISCRIMINATION 01 natural sciences DIOXIDE EXCHANGE LEAF Life Science 0105 earth and related environmental sciences 2. Zero hunger [SDU.OCEAN]Sciences of the Universe [physics]/Ocean PRODUCTIVITY Atmosphere [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere PHOTOSYNTHESIS 15. Life on land ATMOSPHERE [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment 6. Clean water REDUCTION 13. Climate action [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces environment John B. Miller, Bruce H. Vaughn, Henrique F. Duarte, David Wårlind, Philippe Ciais, Dan Zhu, Ivar R. van der Velde, Ivar R. van der Velde, Anne Verhoef, Ingrid T. van der Laan-Luijkx, James W. C. White, Pier Luigi Vidale, Erik van Schaik, Pieter Tans, Kevin Schaefer, Michiel K. van der Molen, Wouter Peters, Wouter Peters, Marko Scholze, 2018-08-27 journalpaper Severe droughts in the Northern Hemisphere cause widespread decline of agricultural yield, reduction of forest carbon uptake, and increased CO2 growth rates in the atmosphere. Plants respond to droughts by partially closing their stomata to limit their evaporative water loss, at the expense of carbon uptake by photosynthesis. This trade-off maximizes their water-use efficiency, as measured for many individual plants under laboratory conditions and field experiments. Here we analyze the 13C/12C stable isotope ratio in atmospheric CO2 (reported as δ13C) to provide new observational evidence of the impact of droughts on the water-use efficiency across areas of millions of km2 and spanning one decade of recent climate variability. We find strong and spatially coherent increases in water-use efficiency along with widespread reductions of net carbon uptake over the Northern Hemisphere during severe droughts that affected Europe, Russia, and the United States in 2001-2011. The impact of those droughts on water-use efficiency and carbon uptake by vegetation is substantially larger than simulated by the land-surface schemes of six state-of-the-art climate models. This suggests that drought induced carbon-climate feedbacks may be too small in these models and improvements to their vegetation dynamics using stable isotope observations can help to improve their drought response. Increased water-use efficiency and reduced CO2 uptake by plants during droughts at a continental scale 10.1038/s41561-018-0212-7