Climate Models May Underestimate Future Rainfall Impacts in India

A recent study has revealed that the CMIP6, a prominent group of climate models used to predict the future impacts of climate change, significantly underestimates the effects of rainfall over India. This finding is crucial as India’s monsoon season becomes increasingly unpredictable.

Historical Context

The CMIP6 models are part of the Coupled Model Intercomparison Projects, which have been instrumental in climate research for decades. These models simulate the interactions between the atmosphere, land, and oceans to project future climate scenarios. The Intergovernmental Panel on Climate Change (IPCC) relies on these models for its Assessment Reports, which guide global climate policies.

Key Findings

Researchers from the Indian Institute of Tropical Meteorology and the National Institute of Technology, Rourkela, have downscaled and bias-corrected the CMIP6 models to generate more accurate regional projections. Their study focuses on the Indian summer monsoon from June to September under various emission scenarios.

1. Downscaling and Bias Correction: The study improved the accuracy of CMIP6 projections by 96% through downscaling and bias correction, which involves refining the model’s resolution and aligning outcomes closer to observed data.
2. Baseline Data: The study used India Meteorological Department (IMD) data from 1980 to 2014 as the baseline for comparison.
3. Sea Surface Temperature: Unlike most other models, this study also included sea surface temperature, a critical factor in monsoon progression.
4. Future Projections: The study found that extreme rainfall events are likely to increase significantly:
   • Near Future (2030-2060): A 14% rise in extreme rainfall events under high emissions scenarios.
   • Far Future (2060-2100): An 18% rise in extreme rainfall events under high emissions scenarios.
   • Extreme Rainfall Thresholds: Projected to be 21% higher in the far future under high emissions scenarios.
5. Duration of Rainfall Events: Before 2060, short-duration extreme rainfall events will be more frequent. After 2060, long-duration events will become more common, potentially leading to sustained high water levels in rivers and reservoirs.

Implications

The study underscores the need for more accurate climate models to formulate effective national climate change adaptation policies. It also highlights the increasing erratic nature of India’s monsoon season, which has significant implications for agriculture, water resources, and disaster management.

Summary in Bullet Points

• CMIP6 Models: Found to underestimate future rainfall impacts in India.
• Downscaling and Bias Correction: Improved model accuracy by 96%.
• Baseline Data: Used IMD data from 1980 to 2014.
• Sea Surface Temperature: Included in projections for the first time.
• Future Projections:
  • 14% rise in extreme rainfall events (2030-2060) under high emissions.
  • 18% rise in extreme rainfall events (2060-2100) under high emissions.
  • 21% higher extreme rainfall thresholds in the far future under high emissions.
• Duration of Rainfall Events: Shift from short-duration to long-duration events after 2060.
• Erratic Monsoon: Increasing unpredictability of India’s monsoon season.

This study is a critical step towards understanding and mitigating the impacts of climate change on India’s monsoon, which is vital for the country’s agriculture and water resources.