Global Warming and Pacific Decadal Oscillation Could Increase Frequency of Equatorial-Origin Cyclones

August 29, 2023

A recent study in Nature Communications suggests that global warming and a cyclical event known as the Pacific Decadal Oscillation (PDO) could increase the frequency of tropical cyclones originating near the Equator. The number of such cyclones was 43% fewer in the years 1981-2010 compared to 1951-1980 due to the PDO being in a ‘warmer’ or positive phase. The study warns that as the PDO has entered a cooler, negative phase since 2019, more tropical cyclones may occur in the post-monsoon months near the Equator.

How does the Pacific Decadal Oscillation (PDO) affect the frequency of equatorial-origin cyclones?

The PDO, which is a long-term ocean-atmosphere phenomenon, has different phases—positive and negative. The study found that when the PDO is in a positive or ‘warmer’ phase, there are fewer tropical cyclones originating near the Equator. Conversely, when the PDO enters a cooler, negative phase, as it has since 2019, it may lead to an increase in such cyclones.

How does global warming interact with PDO in influencing cyclone frequency?

While the study doesn’t provide explicit details on the interaction between global warming and PDO, it does suggest that the combination of global warming and the cyclical nature of PDO could make tropical cyclones originating near the Equator more frequent in the coming years. Global warming may increase sea surface temperatures, which, coupled with a negative phase of PDO, could create conditions more conducive to cyclone formation and intensification.

How does the El Nino Southern Oscillation (ENSO) differ from PDO, and what are their respective impacts on India’s climate?

ENSO is a shorter-term ocean-atmosphere phenomenon in the Pacific Ocean that repeats over two to seven years, while PDO has a longer cycle of about 20-30 years. El Nino leads to reduced rainfall in India, while La Nina is linked to excessive rainfall. PDO, however, isn’t an annual occurrence and is determined only after several years of measuring ocean temperatures and their atmospheric interactions. According to the study, ENSO with a positive PDO generally leads to less rain in India, but when linked with a negative PDO, it brings more rain to the country.

How might an increase in the frequency of equatorial-origin cyclones affect South Asian countries like India and Sri Lanka?

An increase in the frequency of these cyclones could lead to more frequent and possibly more intense weather events, including heavy rains, strong winds, and flooding. This would have broad implications for agriculture, infrastructure, and public safety in South Asian countries. Emergency response systems would need to be better prepared, and more investments would likely be needed in climate-resilient infrastructure.

What steps can be taken by the affected countries to prepare for the increased frequency of these cyclones?

Countries can invest in advanced meteorological technologies for early warning, build climate-resilient infrastructure to withstand extreme weather events, and improve emergency response capabilities. Public awareness campaigns can also educate communities on how to prepare for and respond to cyclones. Regional cooperation for sharing meteorological data and best practices can further aid in preparedness and response.

How significant are the rainfall deficits already recorded in central and southern India, and what might these indicate?

The rainfall deficits of 7% in central India and 17% in southern India are concerning, as they could lead to water scarcity, agricultural losses, and other climate-related challenges. These deficits are linked to the currently developing El Nino and may indicate a more complex interplay of climate variables affecting the Indian subcontinent, including the potential for more frequent or intense cyclones near the Equator in the coming years.

« Previous Post Next Post »