🎒 Climate Change Impact Assessment

This lesson builds core elective concepts in BSc Agriculture with practical applications and exam-oriented clarity.

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Climate Change Impact Assessment

Climate change poses a fundamental threat to global food security. Crop simulation models, combined with climate projections, provide a scientific framework for assessing impacts and planning adaptation strategies.

Climate Scenarios

Climate projections are based on scenarios that describe future greenhouse gas concentrations:

RCP (Representative Concentration Pathways)

Scenario	CO2 by 2100	Temperature Rise	Description
RCP 2.6	421 ppm	1.0 degrees C	Strong mitigation
RCP 4.5	538 ppm	1.8 degrees C	Moderate mitigation
RCP 6.0	670 ppm	2.2 degrees C	Limited mitigation
RCP 8.5	936 ppm	3.7 degrees C	Business as usual

SSP (Shared Socioeconomic Pathways)

The newer CMIP6 framework combines SSPs with forcing levels:

• SSP1-2.6 — sustainability pathway with low emissions
• SSP2-4.5 — middle of the road scenario
• SSP3-7.0 — regional rivalry with high emissions
• SSP5-8.5 — fossil fuel-intensive development

Crop Model Projections

Crop models are run with downscaled GCM outputs (from models like HadGEM, MIROC, GFDL) to project future yields:

• Method — baseline climate (1980-2010) vs. future climate (2030s, 2050s, 2080s) using calibrated crop models
• Ensemble approach — use multiple GCMs and crop models to capture uncertainty range

Projected Impacts on Indian Agriculture

Crop	Projected Change by 2050 (RCP 4.5)	Key Risk Factor
Rice	-5 to -15%	Terminal heat stress, water scarcity
Wheat	-6 to -23%	Heat stress during grain filling
Maize	-10 to -20%	Drought and temperature extremes
Soybean	-5 to -12%	Erratic monsoon rainfall
Groundnut	-8 to -15%	Terminal drought

• CO2 fertilisation effect partially offsets yield losses for C3 crops (rice, wheat) — enhanced photosynthesis at elevated CO2
• C4 crops (maize, sorghum) benefit less from CO2 but are more drought-tolerant
• Net effect is still negative due to temperature and rainfall changes overwhelming CO2 benefits

Adaptation Planning

Model-based adaptation strategies evaluated through scenario analysis:

• Shifting sowing dates — advancing wheat sowing by 2-3 weeks to escape terminal heat
• Drought-tolerant varieties — simulated using modified genetic coefficients
• Altered irrigation scheduling — deficit irrigation strategies to cope with reduced water availability
• Crop diversification — replacing high-risk crops with climate-resilient alternatives
• Conservation agriculture — zero-till, residue retention improve soil water storage

Adaptation Effectiveness (Example: Wheat in North India)

Strategy	Yield Loss Reduction
Early sowing (Nov 1 vs Nov 15)	30-40% of projected loss recovered
Heat-tolerant variety	20-30% recovery
Supplemental irrigation	40-50% recovery
Combined package	70-80% recovery

Mitigation in Agriculture

Agriculture contributes approximately 14% of global GHG emissions:

• Methane (CH4) — rice paddies, livestock enteric fermentation
• Nitrous oxide (N2O) — fertiliser application, manure management
• Carbon dioxide (CO2) — land use change, soil carbon loss

Mitigation options:

• Alternate wetting and drying (AWD) in rice reduces CH4 by 30-50%
• Precision nitrogen management reduces N2O emissions
• Agroforestry and conservation agriculture sequester soil carbon
• Biochar application locks carbon in stable form

Integrating climate impact assessment with adaptation and mitigation planning ensures that agricultural systems remain productive and sustainable under changing climatic conditions.

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Summary Cheat Sheet

Topic	Key takeaway
Main focus	Climate Change Impact Assessment — RCP/SSP scenarios, crop model projections, adaptation planning, and mitigation strategies for Indian agriculture.
Section context	Revise this lesson with the rest of System Simulation and Agro-Advisory for stronger conceptual continuity.