What is sea surface temperature rise? How does it affect the formation of tropical cyclones?

Sea surface temperature (SST) rise refers to the increase in the temperature of the uppermost layer of the ocean, primarily caused by global warming due to greenhouse gas emissions. According to Copernicus Climate Change Service, the average global SST for February 2024 was 21.06 degrees Celsius, the highest level since 1979.

## Factors leading to rise in sea surface temperature

##

• Emissions of greenhouse gases– the average global temperature has risen at least 1.2 degree Celsius above pre-industrial times.  Almost 90% of the extra heat trapped by GHGs has been absorbed by the oceans


• El Niño Events: TheEl Niño–Southern Oscillation (ENSO)leads to periodic warming of the central and eastern Pacific Ocean.


• Ice Melt: The melting ofpolar ice caps and glaciersreduces the reflection of sunlight (albedo effect), causing more heat to be absorbed by the ocean, raising sea surface temperatures.


• Natural Variability:While human activities are the primary driver of recent ocean warming, natural factors such as volcanic eruptions, changes in solar radiation, and ocean currents also play a role in short-term variations in ocean temperature, however these effects intensified by anthropogenic emissions.

## How does rising of sea surface temperature leads to formation of Tropical Cyclones

Sea surface temperature rise leading to the formation of cyclones

Cyclones are caused by atmospheric disturbances around a low-pressure area distinguished by swift and often destructive air circulation. Cyclones are usually accompanied by violent storms and bad weather.

• Tropical cyclones derive theirsource of energy—heat and moisture—from the warm waters of the ocean.


• High sea surface temperatures (SSTs) of magnitude 28–29°C and above provide favorable conditions for the genesis and evolution of cyclones, Eg.Sea surface temperatures (SSTs) leading to cyclogenesis in the Arabian Sea are 1.2–1.4°C higher in recent decades, compared to SSTs four decades ago.


• Rising Warm Air:Warm, moist air near the ocean surface rises, creating a low-pressure area that draws in cooler surrounding air.


• More intense storms– Thedifference in temperature between the ocean’s surface and the upper airenergizes tropical storms. Warmer SSTs increase this difference, which can lead to larger, faster, and more powerful storms.


• More category 4 and 5 storms– The IPCC predicts that as the world warms, a higher proportion of tropical cyclones will reach Category 4 and 5, the most intense categories.

Adopting aSix-Sector Solution,developed by UNEP to reduce GHG Emissions and achieve Paris Agreement commitments is the need of an hour.

Click to Access Full Notes