Journal Article 142M471B3J Carbon Dioxide Research Support, Non-U.S. Gov't climate change impact food security model intercomparison uncertainty 059QF0KO0R 1.5°C warming AgMIP Grain Proteins N762921K75 Nitrogen Research Support, U.S. Gov't, Non-P.H.S. Water [CO2] climate climate change climate change adaptation crop models ecophysiological model ensemble mean ensemble median ensemble modeling extreme low yields grain protein maize model ensemble multimodel ensemble