1. © Crown copyright Met Office Case Study: Use of GLAM to investigate future crop yields over India

2. © Crown copyright Met Office

3. Introduction Climate change will have both direct and indirect influences on crop growth and development i.e. direct CO 2 effect + indirect effect of weather and climate change Regional focus on groundnut (i.e. peanut) crops over Indian subcontinent Aims of study: Identify indirect processes that are important in determining crop yield under climate change Identify key uncertainties in crop yield projections

4. © Crown copyright Met Office Methods Domain choice over Indian subcontinent (4 regions) Use of GLAM over India has shown promising results for the current climate Data for the future climate state is taken directly from PRECIS regional climate simulations performed by IITM Follows SRES A2 emissions path for 2071-2100 Specific input data: solar rad., rainfall, Tmax and Tmin Future climate data from PRECIS suggests enhanced monsoon, higher surface temperatures, and increased atmospheric water content

5. © Crown copyright Met Office Methods

6. © Crown copyright Met Office Methods GLAM contains parameterisations of how crops respond to weather and climate 36 GLAM simulations for 2071-2100 18 with variable-duration crop 18 with fix-duration crop with respect to baseline info Fixed-duration experiments assess indirect impact of elevated CO 2 on crop yield (primarily due to increased VPD - next slide) Excludes impact of mean T on duration Variable-duration experiments assess impact of mean temperature changes (specifically exceedance of Topt) on crop yield

7. © Crown copyright Met Office Vapour pressure deficit (VPD) VPD = difference (deficit) between the amount of moisture in the air and how much moisture the air can hold when it is saturated For this study, VPD is estimated two ways Based on mean daily temperature and relative humidity Based on Tmax and Tmin ↑ in VPD related to ↑ in temperature: Mean temperature, which allows atmosphere to retain more moisture Diurnal temperature range (Tmax minus Tmin) Would lead to reduced crop yields due to enhanced water stress

8. © Crown copyright Met Office Fixed-duration results Increase in T (mean and diurnal) Increase in sat. vapour pressure Increase in VDP Decreased crop yield from reduced transpiration efficiency

9. © Crown copyright Met Office Variable-duration results Increase in T > Topt (28° C in GLAM) Slower crop development Longer crop duration Increased crop yield (more so for irrigated crops)

10. © Crown copyright Met Office Uncertainty in results Variability in yield response to climate change is comparable in magnitude to the mean simulated change This is more pronounced in simulations of exceeding Topt Confidence is highest for regions which do not exceed Topt (project large decreases in crop yield) Results can still be used to suggest implications for future assessments of crop yield under climate change When comparing results with other crop models, there is some agreement in projection of crop yield reduction over India

11. © Crown copyright Met Office Summary In general over India, crop yields are projected to decrease with climate change This is due to ↑ VPD, which reduces water availability When T>Topt, crop yield increases for both rainfed and irrigated crops (but more so for irrigated) Due to longer crop duration More research is needed into crop response to super- optimal temperatures, and more processes-based studies on the impact of VPD

12. © Crown copyright Met Office Questions