The impact of climate change on crop yield without adaptation projected in the 21st century is generally negative even with the CO2 fertilisation effects, with the overall median per-decade effect being -2.3% for maize, -3.3% for soybean, -0.7% for rice and -1.3% for wheat, which is consistent with previous IPCC assessments . The effects vary greatly within each crop, timeframe and RCP, but show a few common features across crops . Differences in the projected impacts between RCPs are not pronounced by mid-century. From then onward, the negative effect becomes more pronounced under RCP8.5, notably in maize. Rice yields show less variation across models than other crops presumably because simulations are mostly under irrigated conditions. A part of the uncertainty in the projection is due to regional differences . Negative impacts on cereals are projected in Africa and Central and South America at the end of the century, which agrees with the previous studies .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report