UPSC mains 2024 GS paper 1: What is sea surface temperature rise? How does it affect the formation of tropical cyclones? (Answer in 150 words)

 Sea surface temperature rise refers to the warming of the ocean's upper layer, driven mainly by increased greenhouse gas emissions. As the sun heats the ocean, warmer waters lead to higher evaporation rates, intensifying moisture in the atmosphere. This phenomenon plays a crucial role in tropical cyclone formation.

Tropical cyclones, including hurricanes and typhoons, require warm ocean waters (typically above 26°C) to generate the energy needed for their development. As sea surface temperatures rise, it increases the likelihood of more frequent and intense storms. Warmer waters provide additional heat and moisture, fueling stronger convection currents, which amplify the cyclone's wind speeds, rainfall, and destructiveness.

Moreover, elevated sea temperatures also affect cyclone duration and the extent of their impact, with storms lasting longer and penetrating further inland. The rise in sea surface temperatures, therefore, significantly influences global weather patterns and the intensity of extreme weather events.

in Details:

What is Sea Surface Temperature (SST) Rise?

Sea Surface Temperature (SST) refers to the temperature of the top layer of the ocean, which interacts with the atmosphere above. It is a crucial indicator of climate patterns and ocean health. The rise in SST refers to the gradual increase in this temperature, typically due to global warming. Human activities, particularly the emission of greenhouse gases like carbon dioxide and methane, trap heat in the Earth's atmosphere, which in turn warms both the land and oceans. This warming has been consistently measured over the past century, with ocean temperatures rising by approximately 0.13°C per decade since the 1970s.

Causes of SST Rise

The increase in sea surface temperature is primarily driven by:

1. Greenhouse Gas Emissions: Excessive burning of fossil fuels (coal, oil, gas) adds greenhouse gases to the atmosphere, trapping heat.
2. Deforestation: Reducing forests decreases the planet's ability to absorb carbon dioxide, increasing atmospheric warming.
3. Melting of Polar Ice: As ice caps and glaciers melt due to warmer temperatures, they reduce the Earth's reflective surface, causing more heat to be absorbed by oceans.
4. Natural Climate Variability: While most warming is human-induced, natural phenomena like El Niño also cause temporary spikes in sea surface temperatures.

Impacts of SST Rise

The rise in sea surface temperature affects marine ecosystems, coastal communities, and atmospheric conditions. For instance:

• Coral bleaching: Corals are highly sensitive to temperature changes, and even small increases in SST can cause them to expel symbiotic algae, leading to coral bleaching.
• Rising sea levels: Warmer water expands, contributing to sea level rise, which threatens coastal areas.
• Changes in marine species distribution: Fish and other marine species migrate to cooler waters, disrupting ecosystems and fisheries.

SST Rise and Tropical Cyclone Formation

Tropical cyclones—which include hurricanes, typhoons, and cyclones—are powerful storms that form over warm ocean waters, primarily in tropical regions. The relationship between SST rise and tropical cyclones is significant because warm ocean water acts as the fuel for these storms. Here’s how SST rise affects tropical cyclones:

1. Energy Source for Cyclones: Tropical cyclones derive their energy from the latent heat of condensation released when warm, moist air rises over the ocean surface. As sea surface temperatures rise, there is more moisture in the atmosphere, providing more energy for cyclone formation and intensification.

   • Generally, a sea surface temperature of at least 26.5°C is required to sustain the formation of a tropical cyclone. When SST exceeds this threshold, it enhances the storm’s strength and size.

2. Increased Cyclone Intensity: The warmer the ocean, the more intense the tropical cyclone. As SST increases, the energy available to the cyclone rises, resulting in higher wind speeds, lower central pressures, and greater storm surge.

   • Studies indicate that tropical cyclones have become more intense and destructive due to warming oceans. For example, Category 4 and 5 hurricanes, the most destructive, have increased in frequency in the past few decades.

3. More Moisture, More Rain: Warmer water increases the amount of water vapor in the atmosphere, which can lead to more intense and prolonged rainfall during cyclones. This can exacerbate flooding, landslides, and infrastructure damage in coastal areas.

4. Shifting Formation Zones: As sea surface temperatures rise, tropical cyclone formation zones are shifting poleward. This means regions that previously didn’t experience cyclones, or only experienced them rarely, may now see more frequent and stronger storms.

   • For instance, in the North Atlantic, the warming of subtropical waters has contributed to more storms reaching higher latitudes, threatening areas that have not historically been vulnerable.

5. Cyclone Duration and Speed: With warmer oceans, tropical cyclones may maintain their strength for longer periods and travel further inland. Rising SSTs have also been linked to changes in storm speed, with some storms stalling or slowing down, leading to extended periods of rainfall and storm surges.

Global Patterns and Future Projections

Regions such as the Atlantic and Pacific Oceans have already shown trends of increasing sea surface temperatures, contributing to more frequent and intense tropical cyclone activity. Scientific models predict that SST will continue to rise throughout the 21st century, further amplifying tropical cyclone risks. These projections suggest:

• More frequent Category 4 and 5 storms.
• Longer cyclone seasons as the warm ocean waters persist for longer periods.
• Increased coastal vulnerability due to stronger storm surges and flooding.

Mitigating the Impacts of SST Rise

To mitigate the impacts of sea surface temperature rise and its effect on tropical cyclones, a combination of global climate action and local preparedness is necessary. Reducing greenhouse gas emissions, transitioning to renewable energy sources, and investing in climate adaptation measures can help limit future SST rise. Additionally, improving early warning systems, building resilient infrastructure, and planning for coastal evacuations can minimize the damage from increasingly powerful storms.

Conclusion

The rise in sea surface temperature is a clear indicator of climate change, and its impact on the formation and intensification of tropical cyclones cannot be overstated. As SSTs continue to climb, the world is likely to face more destructive and frequent tropical storms. Addressing the root causes of warming and preparing vulnerable communities for these enhanced risks will be crucial in the years to come.