Monsoon floods: Worst may be yet to come
IT is early August, 2022, more than a month after Pakistan’s summer monsoon rainfall officially began on June 29th (though heavy rains started happening on the 14th).
By early July, the country received 87% higher than normal rainfall for this time of year. Since then, unprecedented spells of rainfall and devastating flooding have continued unabated, especially in Balochistan and Sindh.
Monsoon rains have been picking up strength much earlier than usual, with the authorities saying they have already reached in July what is usually their peak strength.
As a result, 500 people have died in the last six weeks and 40,000 houses and 2,500 kilometres of road have been damaged or destroyed.
It is already a major disaster. However, this is still just the beginning. The bulk of Pakistan’s monsoon rainfall is usually from late July to the end of August.
On that basis, we should expect the rainfall we are experiencing now to worsen or at least continue in the coming month.
But how much worse is it likely to get? One indicator to base our expectations on is La Nina, a climate phase in which the western Pacific warms in relation to the east, strengthening the South Asian monsoon and making floods in Pakistan more likely.
One of the strongest La Nina events on record started in 2010, the same year as Pakistan’s unfortunate “super-flood”.
Another La Nina, considered the strongest since 2010, began in late 2020 and dissipated in early 2021.
It returned in late 2021 and has remained since. Pakistan’s monsoon season was severe in 2020, not so much in 2021. But 2022’s La Nina is in itself extraordinary.
It did not dissipate as expected in spring of 2022, and continues to be quite strong today. Weather agencies around the globe forecast a high chance that it will continue throughout August, could even last until 2023.
If it does so, that would be the first time since 1998-2001 that La Nina lasted for three consecutive years.
1975 (a year of major flooding for Pakistan) was the last time that a La Nina strengthened instead of weakening in its third year.
The current La Nina looks like its on track to do the same. Pakistan should remain on high alert. An epic La Nina event is happening right alongside the entire summer monsoon season.
The fact that La Nina has already been happening for two years could exacerbate its current effects.
It has likely caused Pakistan’s heavy rainfall in July. But La Nina, part of the ENSO climate cycle, is not the only climate cycle to watch out for.
There is also the Indian Ocean Dipole, and meteorologists say it is right now in a negative phase, when the western Indian Ocean is colder than the east.
There isn’t very clear information about how the IOD affects South Asia’s monsoon. Scientists usually state that a negative IOD decreases the strength of the monsoon, which must be because colder waters near the Arabian Sea contribute less rain.
There was a negative IOD last year as well, probably sparing Pakistan a worse monsoon. But some recent reports in Pakistan’s press say the negative IOD is giving a boost to Pakistan’s rainfall.
That must be because high-pressure over the oceans increases evaporation and sends the moisture straight towards South Asia.
There is a lot of study that needs to be done on this subject. One example from history should be noted.
Before 2021, the last time there was La Nina and negative IOD at the same time was in 2010.
Both started in the summer at the same time as the massive flooding in Pakistan raged, before the negative IOD ended in November while La Nina dissipated next year in spring 2011, resuming later same year.
Extreme weather events of 2010 and 2011 that are linked to that La Nina and negative IOD are being repeated today.
That includes a severe drought that began in East Africa in 2010 and lasted into the next year, leading to a massive region-wide famine beginning in summer 2011, along with historic floods in eastern Australia in late 2010.
Fast forward to the present and both events on a similar scale are happening now. That must mean that the negative IOD conditions occurring since 2021 and the La Nina conditions occurring since 2020 are having similar effects on the weather as they did back in 2010, particularly in the Indian Ocean, the source of Pakistan’s monsoon.
Both La Nina and negative IOD tend to lessen rain in East Africa and increase it in Australia, but what is happening now is extreme.
That alone should give Pakistan reason for concern. Ever since La Nina began in 2020, extreme weather events have been very common, especially those linked to the jet-streams.
And many of those events were similar to what happened in the La Nina years 2010, 2011, and 2012.
For example, 2022 has seen an abundance of heat waves all around the world, including record-breaking ones in Europe caused by high air pressure.
Similarly, 2010 was year of prolific heat waves, and one high-pressure zone in western Russia was linked to Pakistan’s floods.
Even Pakistan’s current flooding shares unique features with the country’s 2010 floods, with rainfall extending to usual shadow zones in Balochistan, KP, and Gilgit-Baltistan.
With everything that has been going on for more than two years, especially in 2022, there is every reason to believe Pakistan faces an extremely high chance of a severe monsoon, even a disaster reminiscent of 2010. We must continue to be vigilant.
—The writer is Director at Pakistan’s People Led Disaster Management.