Asia burning: From El nino 'frying pan' to climate change 'fire'

The capital has been enduring a stint of vicious heatwave for at least two weeks now. The temperature has hit the 40 ⁰C mark a few times already. 

You may have been feeling like dry hot sand is being thrown at you, or you are standing before an air-con exhaust fan that exclusively blows hot air. The weather in both April 2023 and 2024 has had this common aspect. 

This is unlike anything anyone in Bangladesh can recall in recent memory. 

As part of the greater tropical region, this was, and still is, the case for the rest of especially South- and Southeast Asia too.

The 2023 extreme Asian summer was mainly because of the natural phenomenon known as El Nino Southern Oscillation, ENSO, or simply El Nino. The National Oceanic and Atmospheric Administration (NOAA) in the US says that ENSO has weakened since the beginning of 2024. 

The heatwave currently blowing over this region is partially due to the residual effects of ENSO, which should be followed by a period of heavy rainstorms known as La Nina later this year. 

However, a closer look will reveal that human-made climate changes exacerbated the 2023/24 ENSO effects if we compare the current episode to the previous ones.

Asia facing the blow, but why exactly

It is because natural meteorological events put Asia in a place where it can only see itself jump from the tropical 'frying pan' to the ENSO 'fire'.

Briefly, ENSO is a natural event that happens in a cyclical fashion—once every 7-9 years. This global climate phenomenon originates from the variations in sea surface temperature and wind direction over the tropical Pacific Ocean.  

Along the equator, strong natural trade winds blow surface seawater from the eastern pacific (the closest shore is in the Americas, broadly) towards the western pacific (Northeast Australia). 

Due to the difference in ocean surface and the thermocline (a transition layer between the warmer water at the surface and the cooler water below), the water and the air over the water surface along the West Pacific coast is more humid with moisture. This explains the tropical weather in Australia as well as the entire Southeast Asia (the latter is the closest point to Australia).  

But this way of the trade wind flow weakens over years, and ENSO begins. This means that the warmer water and hot air over the surface shifts from the Western Pacific towards further east. 

Around that time, the air around the West Pacific coast is drier – which means less rain, increased dryness, and uninterrupted sun towards this region during the summer and beyond. 

While ENSO's effect may be directed towards Australia and Southeast Asia, the presence of the Indian Ocean and its own interesting natural plays ensure that the wrath is felt in South Asia too. 

In a 2014 American Meteorological Society publication in the Journal of Climate titled The curious case of Indian Ocean warming, Roxy and coworkers noted that the Indian Ocean has been warming throughout the last century by 1.2 ⁰C. 

The authors used climate modelling to conclude that while the recent global warming has been a cause to blame, the prime reason was the "asymmetry in El Nino Southern Oscillation (ENSO) teleconnection".

If you take a look at a world-map, the Indian Ocean joins the Pacific Ocean near Tasmania, Australia.  

Climate change is amplifying ENSO in Asia

Scientists cautiously suggest that the ENSO episodes in the last decade are being felt much more severely thanks to the increasing human-induced climate changes. 

Such as, the 2017 Nature Communications article penned by Thirumalai and coworkers. The title is self-explanatory enough, "Extreme temperatures in Southeast Asia caused by El Nino and worsened by global warming".

Based on data between 1940 and 2016, their global warming simulation results strongly suggested that "global warming increases the likelihood of record-breaking April extremes, where we estimate that 29% of the 2016 anomaly was caused by warming and 49% by El Nino".

This was noted by the Intergovernmental Panel on Climate Change, IPCC too – at its fifth assessment report pointed out that 90% of the heat due to global warming has been accumulated in the oceans. 

It is interesting to note that in Australia, the 1997-98 ENSO clocked a higher temperature on average compared to 2023-24. However, 2023 saw the driest three-month period ever.  

Perth saw the highest temperature in its history peaking to 41 ⁰C in January 2024. However, around the same time, parts of New South Wales recorded more than half a year's worth of rain in just two days. You may recall the recent stormy rain and flash floods in the middle-east. 

Such contrasting weather behaviour is strongly linked to climate change consequences. 

This sentiment was echoed by a 2023 Nature Review article authored by researchers from China, Australia, and the US. They write that ENSO episodes have been more frequent and rougher since 1960. The main culprit, their climate simulations spanning 1901-2020 reveal, is the human-made greenhouse gas emissions. 

Now let us take a deeper look at how the temperature intensified within a span of 7-8 years. 

According to the Norway-based climate website timeanddate.com, in the last two weeks, Bangkok recorded an average of 38.2 °C, the highest daytime temperature. Even at a point when El Nino has subsided significantly, this is much higher than the average April 2015 one (daytime highest average of about 36 ⁰C) and even last year (37.4 ⁰C).

At the Mekong-Delta, the 'rice-bowl' in southern Vietnam, the temperature soared between 37 and 38 ⁰C for the last two weeks. In April 2015, this hovered between 33 to 36 ⁰C for most of the days.

News from the last two weeks show the scenario is just like this throughout the entire Southeast Asia. 

In Manila, the capital of Philippines, children were let play in custom-made swimming pools by filling large commercial cartons with water. Going even further towards East Asia, such as areas in Taiwan – an unprecedented dry weather with 39 ⁰C temperature has been the recent norm.

In India, Kolkata hit the 41-42 ⁰C mark this week. Except for a few places in South India, the rest of India is similarly burning too.  

Now, when it comes to Dhaka, April 2015 only had a few days hitting 35 ⁰C temperature. This year, and also last year, though – extreme dryness with 38 – 40 ⁰C temperatures were commonplace.  

When both the World Meteorological Organisation (WMO) and NOAA suggested that El Nino is in decline since February 2024, these scorching numbers point towards the fact that human-made global warming may have intensified the already severe ENSO effects lately.