Severe floods are ravaging Pakistan due to a combination of heavy monsoon rains and melting glaciers. While deadly floods are no stranger to Pakistan, this event is particularly horrific with more than 1,100 people killed so far and several million more affected.
Pakistan’s climate official said a third of the country is under water - an area larger than the state of Victoria.
This Northern Hemisphere summer has seen extreme weather events after extreme weather events, from record droughts in Western Europe, the United States and China to floods in Japan and South Korea.
This begs the question of the extent to which climate change is to blame. And if so, is that what we should expect from now on?
extreme summer
The floods in Pakistan are the latest in a series of extraordinary disasters in the northern hemisphere.
Western Europe and central and eastern China experienced record heat waves and droughts that led to water restrictions. These heat waves and droughts have also caused crop shortages, driving up food costs around the world.
China has fallen into an energy security crisis. The longest river in Italy flows at one tenth of its usual rate. Droughts and their significant impacts are expected to continue for the foreseeable future.
The torrential rains caused flooding in places ranging from Dallas in the United States to Seoul in South Korea, which experienced the heaviest torrential rains in a century.
Record maximum temperatures were also recorded in Japan, the central United States and the United Kingdom, where temperatures exceeded 40 degrees Celsius for the first time.
It’s only been a few months since we saw temperatures reach 50°C before the monsoon rains in northern India and Pakistan.
Put it into perspective
While it is true that many of the extreme events that have occurred this summer have been exceptional, we typically see more extreme weather events in the Northern Hemisphere summer than at any other time. This is because extreme temperatures, very heavy rain, and drought are more likely at the warmest time of the year.
Two-thirds of the planet’s land and more than 85% of the world’s population are located in the northern hemisphere. This means that there are more people affected by severe weather than in the Southern Hemisphere, making the Northern Hemisphere summer the time for disasters with severe impacts.
In addition, extreme weather events can occur at the same time in different places, due to large-scale atmospheric waves called “Rosby waves”, a naturally occurring phenomenon, such as La Niña and El Niño.
In 2010, western Russia experienced extreme heat and wildfires while Pakistan experienced some of the worst floods to date. These events were associated with a Rossby wave that caused the high pressure pattern to falter over western Russia and low pressure to continue over Pakistan.
Rossby waves can also create heat waves at the same time, thousands of kilometers away. Earlier this Northern Hemisphere summer, we saw simultaneous heat waves hitting the western United States, western Europe and China.
Rossby’s waves may have contributed to simultaneous disasters this summer, but it’s too early to say for sure.
Climate change and endless extremes
With so many extreme weather events causing mass deaths and significant economic and environmental problems, it is worth considering whether climate change might make these events worse.
Human-caused climate change has warmed the planet by about 1.2°C so far, and this has caused an increase in the frequency and intensity of some types of extreme weather, particularly extreme heat waves and record high temperatures.
Every heat wave in today’s climate has a climate change footprint caused by greenhouse gas emissions. Indeed, rapid analyzes have already established that human influence on climate has significantly increased the likelihood of extreme heat in India and Pakistan in May, and record-high temperatures in the United Kingdom in July.
Research also shows that climate change is increasing the incidence of Synchronized Heat waves in the northern hemisphere, mainly due to long-term warming.
It is unclear whether the Rossby wave pattern causing simultaneous heat waves in different places is becoming more frequent.
Climate change is also altering rainfall patterns exacerbating droughts in some areas, such as in much of Western Europe.
Heavy rains and short-lived heavy rains, such as those seen in Seoul and Dallas in recent weeks, are also exacerbated by climate change. This is because global warming results in the air being able to hold more moisture - for every 1 warming, the atmosphere can hold 7% more moisture.
In fact, heavy rains in Pakistan follow a marked trend towards increasing extreme daily precipitation totals. This region of the world is expected to see a continuous intensification of daily and multi-day heavy rain events during the summer, as the planet warms.
The worst things are to come
We can expect more extreme weather events in the coming years as greenhouse gas emissions continue at near-record rates.
Scientists have predicted worsening extreme weather events - especially heat waves - for decades. Now, we see this happening before our very eyes.
Some of the temperature extremes in recent years have been far beyond what we thought would happen after just over 1g of global warming, like the record heat in western North America last summer. But it’s hard to know if our expectations fall short of our expectations of extreme heat.
In any case, the world must prepare for more potentially record-breaking high temperatures in the coming months, years, and decades. We need to decarbonize quickly to reduce the damage from future extreme events.
Andrew King, Senior Lecturer in Climate Science, University of Melbourne
This article has been republished from The Conversation under a Creative Commons license. Read the original article.
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