Warm Climate Means More Floods in Pakistan

Pakistan’s floods this year have led to an overwhelming loss and damage to the country. According to The Economist’s “Devastating floods like Pakistan’s will be more common in a warming world”, the flood resulted in the deaths of more than 1,400 people, displacement of 33 million, 1.7 million homes destroyed, half of its cotton crops damaged, and most of its wheat harvest.

Pakistan’s government estimated the loss to be US$30 billion, equivalent to 9% of its GDP. They wanted the wealthy countries – those who have historically emitted the most carbon dioxide into the atmosphere and thus contributed largely to climate change, to extend support.

Climate change (2022) finds that climate change has increased the heavy rains in Pakistan, leading to the flooding of large parts of the country. The country reportedly received more than three times its usual rain in August, making it the wettest month since 1961.

Two of its provinces, Sindh and Balochistan, receive 7 to 8 times more rain than their average monthly total, causing the Indus River that runs the country’s length to burst its banks, while the intense rainfall caused flash floods in urban areas.

Sindh, the worst hit province, is home to 50 million Pakistanis, where floodwaters covered acres of farmland at a regional airport from late August to early September 2022.

Temperature increases of 1.2°C brought more rainfall and accelerated the glacial melt in northern Pakistan.

Aside from the rising temperatures creating more rain– when it is hotter, the air tends to pick up more moisture, thus increasing the chances for more rain, the heatwaves that hit Pakistan and India in April and May, about three months before the country’s abnormal monsoon season, has accelerated the melting of northern Pakistan’s glaciers.

Due to GHG emissions, Pakistan’s 7,2000 glaciers are melting faster than in the past. The glaciers in this region, including the Himalayas, are considered the “third pole” because they contain massive ice storage after the north and south poles. Temperature increase in the region is at 0.42°C per decade, warming twice as fast as the rest of the world. Pollution also speeds up ice melts. As dark particles land on ice, it causes the surface to absorb more heat from the sun, thus accelerating the melt.

Satellite images used by researchers revealed that from 2000 to 2019, northern Pakistan shrank by 4.6 gigatons, equivalent to around 1.8 million Olympic swimming pools annually.

The tragic floods in Pakistan are likely to become more frequent or even worsen. Even with a temperature rise of 2°C by 2100, a third of the Himalayas could disappear, resulting in enormous suffering for developing countries or those that contributed the least to climate change.

Climate change (2022) highlights their main findings:

• “The flooding occurred as a direct consequence of the extreme monsoon rainfall throughout the summer 2022 season, exacerbated by shorter spikes of very heavy rain, particularly in August, hitting the provinces Sindh and Balochistan. We, therefore, consider 60-day and 5-day maximum rainfall during the monsoon season for the Indus basin and the two provinces, respectively.”
• The devastating impacts were also driven by the proximity of human settlements, infrastructure (homes, buildings, bridges), and agricultural land to flood plains, inadequate infrastructure, limited ex-ante risk reduction capacity, an outdated river management system, underlying vulnerabilities driven by high poverty rates and socioeconomic factors (e.g. gender, age, income, and education), and ongoing political and economic instability.
• The return time for both events defined above is about 1 in 100 years in today’s climate. However, rainfall in the Indus basin is extremely variable from year to year due to, amongst other drivers, the strong correlation with the ENSO cycle. Thus, exact quantification is difficult.
• First, looking at the trends in the observations, we found that the 5-day maximum rainfall over the provinces Sindh and Balochistan is now about 75% more intense than it would have been had the climate not warmed by 1.2C. In contrast, the 60-day rain across the basin is now about 50% more intense, meaning rainfall this heavy is now more likely to happen. There are significant 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.
• Secondly, to determine the role of human-induced climate change in these observed changes, we looked at the trends in climate models with and without the human-induced increases in greenhouse gases. The regions involved are at the extreme western end of the monsoon region, with large differences in rainfall characteristics between dry western and wet eastern areas.
• Many of the available state-of-the-art climate models struggle to simulate these rainfall characteristics. Those that pass our evaluation test generally show a much smaller change in the likelihood and intensity of extreme rainfall than the trend we found in the observations. This discrepancy suggests that long-term variability, or processes that our evaluation may not capture, can play an important role, rendering it infeasible to quantify the overall role of human-induced climate change.
• However, for the 5-day rainfall extreme, the majority of models and observations we have analysed show that intense rainfall has become heavier as Pakistan has warmed. Some of these models suggest climate change could have increased the rainfall intensity up to 50% for the 5-day event definition.
• Looking at the future, for a climate of 2 °C warmer than in preindustrial times, models suggest that rainfall intensity will significantly increase further for the 5-day event. At the same time, the uncertainty remains very large for the 60-day monsoon rainfall.
• Our results are in alignment with recent IPCC reports.
• Both current conditions and the potential further increase in extreme peaks in rainfall over Pakistan in light of human-caused climate change suggest an urgent need to reduce vulnerability to severe weather in Pakistan.

To read the entire study, click the link in the “Source” below.