Rainfall event made more likely due to climate crisis caused Pakistan floods

Floods that devastated large parts of Pakistan last month, left tens of thousands homeless and around 1,500 dead was caused due to an intense “one in a 100-year rainfall” event made several times more likely due to climate crisis, according to a World Weather Attribution (WWA) analysis.

WWA, a network of leading climate scientists globally, however, could not quantify how the crisis made the event possible due to variations in the result of climate models. WWA analysed maximum rainfall for a five-day period for Sindh and Baluchistan, Pakistan’s worst-affected provinces, and maximum rainfall for 60 days from June to September to arrive at its findings.

“First, looking just at the trends in the observations, we found that the 5-day maximum rainfall over the provinces Sindh and Balochistan are now about 75% more intense than it would have been had the climate not warmed by 1.2 degree C, whereas the 60-day rain across the basin is now about 50% more intense, meaning rainfall this heavy is now more likely to happen,” WWA said in a statement on Thursday.

It added there are large uncertainties in these estimates due to the high variability in rainfall in the region, and observed changes can have a variety of drivers, including, but not limited to, climate change.

WWA looked at the trends in climate models with and without the human-induced increases in greenhouse gases to determine the role of human-induced climate change. “The scientists found that modern climate models are not fully able to simulate monsoon rainfall in the Indus river basin, as the region is located at the western edge of the monsoon and its rainfall pattern is extremely variable from year to year. Consequently, they could not quantify the influence of climate change as accurately as has been possible in other studies of extreme weather events, such as heatwaves.”

Friederike Otto, a WWA member, cited evidence and said it suggests that climate change played an important role in the event, although the analysis did not allow it to quantify how big the role was. “This is because it is a region with very different weather from one year to another, which makes it hard to see long-term changes in observed data and climate models,” said Otto.

“This means the mathematical uncertainty is large. However, not all results within the uncertainty range are equally likely. What we saw in Pakistan is exactly what climate projections have been predicting for years. It’s also in line with historical records showing that heavy rainfall has dramatically increased.”

Pakistan received over three times its usual rainfall in August, making it the wettest since 1961. Sindh and Baluchistan experienced the wettest August ever, receiving seven and eight times the usual monthly rainfall.

On August 25, Pakistan declared a national emergency estimating preliminary damages exceeding around US$30 billion. The floods followed extreme heat stress in India and Pakistan. WWA in May said the March to April spring heatwave spell in the two countries was about 30 times more likely to happen because of human-caused climate change.

The results of their rapid analysis showed that the unusually long and early onset heatwave spell in India and Pakistan is very rare, with a chance of occurring only once in 100 years.

WWA’s flood analysis was released days after the opening of the United Nations General Assembly (UNGA) on Tuesday. Climate change experts held a briefing on Thursday highlighting how global inflation rise and climate impacts continue to hit the most vulnerable countries. UNGA is expected to set the tone on the urgency of compensating loss and damage or compensation for impacts of extreme climate change events.

Speaking at the briefing World Resources Institute director (climate programme) Ulka Kelkar said the floods in northeast India and Bangladesh this monsoon do not even make it to the top climate events that have happened this year. “What has happened in Pakistan can no longer be unseen. One in seven people in Pakistan has been rendered homeless. You can no longer deny that the issue of loss and damage and adaptation will be central.”

Kelkar said there was a lot of frustration on the matter at the 2021 United Nations Climate Change Conference (COP26). “We heard last year that the delivery of the promised 100 billion dollars from developed nations will be delayed and that was before the Ukraine crisis. Now the delivery seems even more distant. From the developing country perspective, there are two things– hard finance is urgently needed today and we need acknowledgment and solidarity on loss and damage from developed nations.”

UN secretary general Antonio Guterres spoke about adaptation on Wednesday. “G20 countries are responsible for 80% of emissions. They are also suffering the impact of record droughts, fires, and floods – but climate action seems to be flatlining. If one-third of G20 countries was under water today, as it could be tomorrow, perhaps they would find it easier to agree on drastic cuts to emissions. All countries – with the G20 leading the way – must boost their national emissions reduction targets every year, until we limit the world’s temperature rise to 1.5 degrees.”