The relation between climate and agricultural productivity starts from that of carbohydrates dependent on photosynthetic activity and as such any relation between climate and productivity is primarily linked to the relation between photosynthetic yield and the climatic parameters This is the essence of Devanathan ’concept on the relation between climate and productivity On this basis productivity model has been developed and presented. This has been so widely tested by Ranganathan in tea and other crops in India and Sri Lanka as Consultant to IMT technologies Ltd ., Pune. 

Keywords:Climate; Agricultural productivity; Photosynthetic activity.