Summer warmth of the past six interglacials on Greenland

The relative warmth of mid-to-late Pleistocene interglacials on Greenland has remained unknown, leading to debates about the regional climate forcing that caused past retreat of the Greenland Ice Sheet (GrIS). We analyze the hydrogen isotopic composition of terrestrial biomarkers in Labrador Sea sediments through interglacials of the past 600,000 y to infer millennial-scale summer warmth on southern Greenland. Here, we reconstruct exceptionally warm summers in Marine Isotope Stage (MIS) 5e, concurrent with strong Northern Hemisphere summer insolation. In contrast, “superinterglacial” MIS11 demonstrated only moderate warmth, sustained throughout a prolonged interval of elevated atmospheric carbon dioxide. Strong inferred GrIS retreat during MIS11 relative to MIS5e suggests an indirect relationship between maximum summer temperature and cumulative interglacial mass loss, indicating strong GrIS sensitivity to duration of regional warmth and elevated atmospheric carbon dioxide.

Potential impact of elevated atmospheric carbon dioxide and climate change on Victorian wheat marketing grades and value

The potential impact of elevated atmospheric carbon dioxide concentration ([CO2]) and future climate predicted for 2050 on wheat marketing grades and grain value was evaluated for Victoria, Australia. This evaluation was based on measured grain yield and quality from the Australian Grains FACE program and commercial grain delivery data from Victoria for five seasons (2009–13). Extrapolation of relationships derived from field experimentation under elevated [CO2] to the Victorian wheat crop indicated that 34% of grain would be downgraded by one marketing grade (range 1–62% depending on season and region) because of reduced protein concentration; and that proportions of high-protein wheat grades would reduce and proportions of lower protein grades would increase, with the largest increase in the Australian Standard White (ASW1) grade. Simulation modelling with predicted 2050 [CO2] and future climate indicated reduced wheat yields compared with 2009–13 but higher and lower grain quality depending on region. The Mallee Region was most negatively affected by climate change, with a predicted 43% yield reduction and 43% of grain downgraded by one marketing grade. Using 2016 prices, the value of Victorian wheat grain was influenced mainly by production in the different scenarios, with quality changes in different scenarios having minimal impact on grain value.