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Department of Science and Technology (DST)
A new study by Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, and the Indian Institute of Astrophysics (IIA) reveals that water vapor (WV) plays a far more significant role in atmospheric heating than previously estimated, especially when compared to aerosols. Focused on the Indo-Gangetic Plain (IGP)—a global hotspot for high aerosol loading—the research underscores the complex interplay between these two atmospheric components and their impact on the regional climate and the Indian summer monsoon.
Key findings of the study include:
Dominant Heater: Water vapor was found to heat the atmosphere much more intensely than aerosols do, highlighting its outsized role in the energy balance over the IGP.
Aerosol-Free Intensity: The radiative effects of water vapor are significantly more intense in clean, aerosol-free atmospheres, particularly over the Earth’s surface.
Coupled Radiative Effects: When aerosols are present, the water vapor effect shifts its intensity toward the top of the atmosphere, indicating a strong interrelation where aerosols modulate the water vapor radiative effect (WVRE).
Methodological Breakthrough: Researchers utilized data from six AERONET (Aerosol Robotic Network) sites and employed SBDART simulations to refine how atmospheric composition changes influence regional climate dynamics.
What is Water Vapor Radiative Effect (WVRE)? It refers to the change in the Earth’s radiation balance specifically caused by the presence of water vapor, which absorbs outgoing long-wave (thermal) radiation from the Earth and scatters or absorbs incoming solar radiation. Unlike carbon dioxide, which is well-mixed globally, water vapor varies highly in concentration across regions like the IGP, acting as a powerful local “feedback” that amplifies the warming effects of other greenhouse gases and aerosols.
Policy Relevance
The study’s results are vital for the Ministry of Earth Sciences and Environment Ministry in refining climate models and developing more accurate regional weather projections for the Indian subcontinent.
Strategic Impact for India:
Monsoon Prediction: Understanding the coupled role of aerosols and water vapor is critical for improving the accuracy of Indian Summer Monsoon forecasts, which are essential for agricultural planning.
Climate Projections: The findings suggest that future climate models must consider both aerosols and water vapor simultaneously, rather than in isolation, to avoid significant uncertainties in regional temperature projections.
Pollution Control Synergies: As India implements the National Clean Air Programme (NCAP), reducing aerosol loading (pollution) may paradoxically increase the surface-level heating impact of water vapor, necessitating a more integrated approach to air quality and climate management.
Heat Stress Assessment: The research explains how water vapor compensates for the surface “cooling” effect of aerosols, leading to higher heat-humidity indices (wet-bulb temperature) that pose severe health risks during pre-monsoon heatwaves.
Relevant Question for Policy Stakeholders: How will the Department of Science and Technology (DST) integrate these findings into the ‘National Mission on Strategic Knowledge for Climate Change’ to ensure that regional warming projections account for the heightened sensitivity of water vapor in aerosol-free zones?
Follow the full news here: Water vapor heats the atmosphere much more than aerosols do