models have been used . Zhao  introduced a modelling approach that could be used to generate yield projections for a wider range of annual crops. The discussion here also draws on reviews of more restricted experimental studies. Negative impacts of climate change on crop production are expected across many cropping systems . Apart from the direct effects of elevated carbon dioxide, most changes are expected to have negative effects on crop production. Changes in temperature and rainfall are most often mentioned as drivers of climate impacts, but expected changes in phenology, pests and diseases are also raising concerns. Scheelbeek et al.  synthesised projections for vegetables and legumes, based on their response to climate factors under experimental conditions; in most cases, the magnitude of the changes is comparable to the RCP8.5 2100 forecasts. Scheelbeek et al.  projected yield changes of: +22.0%  for a 250 ppm increase in CO2 concentration; - 34.7%  for a 50% reduction in water availability; - 8.9%  for a 25% increase in ozone concentration; - 31.5% for a 4℃ increase in temperature . Overall, impacts are expected to be largely negative in regions where the temperature is currently above 20°C, while some yield gains are expected in cooler regions . Scheelbeek et al.  did not consider changes in pest and disease pressure, which are projected to increase with warming .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report