It was almost midnight on November 11, 2020 when Ulysses (Vamco) made landfall in Quezon Province. The soon to be Category 4 typhoon would bring Luzon鈥檚 dams to failure, flooding both the Marikina and Cagayan River Basins. Water levels of the Marikina River back then exceeded even those during Typhoon Ondoy (Ketsana) which wreaked havoc in 2009.听
When days later, it eventually made landfall in Vietnam, Ulysses had left in its wake nearly 100 people dead and P20 billion worth of damages in the Philippines.听
鈥淚s global warming to blame?鈥� one might ask, perhaps to make more sense of the tragedy. Indeed, as our days and nights get hotter, many Filipinos get the sneaking suspicion that storms like Ulysses are almost ironically getting more violent as a consequence.
Speculating is one thing, but getting hard evidence for our guess is another. If there was only a way to take a typhoon like Ulysses back in time, to see how it would behave in a world less ravaged by global warming. Then, perhaps, we could conclude that rising temperatures have a direct effect on storms of this magnitude and, perhaps, be better prepared.
Historical Warming
Enter Dr. Gerry Bagtasa. Trained in Japan, an atmospheric physicist, Dr. Bagtasa of the UP Diliman College of Science Institute of Environmental Science and Meteorology (IESM), always had a thing for equations. While his meteorologist colleagues might stress on how a typhoon might behave or its effects, Bagtasa aims to study the physical properties and the underlying mathematics of these extreme weather events. The difference is subtle but it exists.
鈥淗ow does reality relate to these equations?鈥� he would ask. It is a question he has had to ask more often as the country finds itself annually battered by stronger storms. And when Ulysses caused massive flooding, everyone from the government to the media blamed a host of causes, none bigger than climate change. But was that really at fault?
Frustrated with the general feeling of resignation, Bagtasa, together with colleagues Rhonalyn Macalalad, Rafaela Jane Delfino, Roy Badilla, and Socrates Paat, decided to find out for themselves. Specifically, they used computer simulations to help answer the question: what would Ulysses look like 40 years ago on a cooler planet?
To create the ideal test, Bagtasa and his team used the Pseudo Global Warming (PGW) method. Bagtasa explains: PGW is a method where, provided you have figures for parameters like sea surface temperature and humidity, you can experimentally recreate a typhoon like Ulysses in another time period and observe its characteristics. Western scientists like Kerry Emanuel and Noah Diffenbaugh have tried before to quantify the relationship between violent storms and rising temperatures. The team wanted to see if the same could be applied here.
For context, Bagtasa knew that ocean temperatures 40 years ago were around 1.6 degrees cooler than they are today. With details like this from high quality data released by the US National Oceanic and Atmospheric Administration (NOAA) and others, they recreated Ulysses in a computer to characterize its convective available potential energy (CAPE) and other variables.
鈥淐louds are formed when moisture rises to the upper atmosphere,鈥� Bagtasa said. 鈥淎nd CAPE basically measures how fast it rises. If we know that moisture is rising and how fast, we can basically answer how much water can go into the clouds.鈥� Bagtasa explains further how there is a phenomenon where water continues to rise despite the clouds virtually bursting with moisture. He said this happened with Ulysses and partly explains why the typhoon brought so much rain.
Using these characteristics, the team compared Ulysses under three conditions: a) a control run with conditions closely mirroring the present; b) a surface sea temperature (SST) run; and, c) a so-called 鈥榟istorical warming鈥� run, which combined the influence on the typhoon of SST, humidity, and environmental temperature from 40 years ago. Observing the influence of sea temperature was especially important, Bagtasa said, since studies had singled it out as a major causal factor in the typhoon intensification.
鈥淭yphoons get their energy from evaporating water,鈥� he explained. 鈥淲hen water evaporates from the sea, it forms clouds. And when the temperature is warmer, the evaporation is faster and much more water gets evaporated. And your typhoon also gets more energy.鈥�
Ever Higher Risk
What did they find? 鈥淪o first we tried modifying just ocean temperatures. If temperatures are around 1.6 degrees higher now, that鈥檚 big. And because of that temperature increase, the typhoon became stronger. Much stronger,鈥� Bagtasa explained.
A similar but interesting result occurred when they compared the historical warming run with the control. Here, you are factoring in not just the temperature of the ocean, but environmental temperature as well. 鈥淪o, when you bring these two together, it was also stronger, but not as strong as when only the ocean temperature changed,鈥� he said. The reason being that the hotter temperature in the environment acted as a counter force, making it harder for water to rise and clouds to form.听
鈥淚n short, it鈥檚 not just warm oceans that control this intensification, the warm environment can de-intensify things a little bit, and stop some moisture from rising,鈥� Bagtas said.
However, make no mistake, even in this more moderate scenario, typhoons like Ulysses are clearly stronger than they were years ago. 鈥淭he intensification still wins out.鈥�
What does this mean for our future? Luckily, the Pseudo Global Warming method also works in reverse. For which reason, in a 2023 paper with Delfino, Pier Luigi Vidale and Chris Hodges, Bagtasa painted a grim picture of the future if a global attitude shift does not happen.听
Using PGW, they tested three of our country鈥檚 most damaging typhoons: Yolanda (Haiyan, 2013); Pablo (Bopha, 2012); and Ompong (Mangkhut, 2018), using three different scenarios for the year 2100: a) a future where renewable energy use is widespread and fossil fuel use is greatly reduced;, b) a future of moderate change; c) and, a zero-change worst case scenario.听
Predictably, putting Yolanda, Pablo, and Ompong in a future with essentially warmer ocean and environmental temperatures, and higher humidity, made their winds and rains much stronger. Moreover, these simulations saw these typhoons recurve, or delay their normal northward path. This means that the path of typhoons will be increasingly unpredictable, putting communities previously unaccustomed to the ravages of violent storms, at ever higher risk.
Are we helpless?
One of the most frustrating things for Bagtasa to explain is the fact that, in the grand scheme of things, the Philippine contribution to global greenhouse gas emissions is tiny. While every bit helps locally, the future of climate change depends mostly on the actions of big players like China, who alone accounts for 27-31% of global emissions.
That news may be disheartening to those who want immediate action. But there is an aspect of mitigation where Bagtasa says we can vastly improve: science communication.
Unlike during the time of Ondoy and Yolanda, we have certainly gone a long way: 鈥淧AGASA has improved a lot when it comes to forecasting,鈥� Bagtasa said. And with each tragedy, the destructiveness of tropical storms becomes more rooted in local memory, helping us to learn and adapt. 鈥淏efore, we didn鈥檛 really care much about water levels, for example. Now, especially after Ondoy, when they say the water has reached a certain level, people know that it鈥檚 time to evacuate.鈥�
However, there are aspects where things can definitely still get better. 鈥淚 think communication should go down all the way to the grassroots,鈥� he said. 鈥淏ecause I see even members of our local government units鈥� (LGU) own disaster response teams, when they attend briefings, they don鈥檛 really understand PAGASA鈥檚 forecast. Which is shocking. And I鈥檓 sure it鈥檚 even worse in far-flung areas.鈥�
Take for example the concept of landfall. 鈥淟andfall indicates that the eye of the storm has moved over land,鈥� Bagtasa said. 鈥淥ne of the mistaken impressions is the idea that you will only be affected by a typhoon when it makes landfall. But a typhoon is not just a single point! It is hundreds of kilometers wide. So even without making landfall, it can actually have an effect, and a devastating one at that.鈥�
鈥淪o, simple things like this. It might seem like common sense to me because it鈥檚 what I study, but it may not be for everyone. We have to ask people how they understand it and slowly change these misconceptions,鈥� Bagtasa concluded.
Read more on Dr. Bagtasa and his team鈥檚 original paper on Ulysses,
Read more on UPD College of Science鈥檚 writeup on his team鈥檚 work on Haiyan, Bopha, and Mangkhut, 听
