Pakistan Floods and Wildfires in Russia – Are They Linked?

During the last month the news has been filled with stories relating to weather and climate, including floods in Pakistan and a heatwave in Russia. It appears that these two apparently disconnected events have a common cause.

According to meteorologists monitoring the atmosphere above the northern hemisphere, unusual holding patterns in the polar jet stream are to blame. A jet stream is a fast-moving current of air that moves around the world at an altitude of around 10 and 12 kilometres above ground. There are two branches usually in place in the northern hemisphere at this time of year: a strong subtropical jet blowing over the Mediterranean and central Asia, and a weaker northern polar jet that blows over northern Europe (and carries with it the low pressure areas that bring the UK most of its rain).

Weather forecasters use the polar jet to predict medium-term temperatures, because it acts as a barrier between cold Arctic air and warmer tropical air. If the polar jet moves north then areas just south of it will be warmer and drier than normal. If it moves south, then areas just to the north will be cooler and wetter.

During July 2010, an exceptionally strong polar jet stream moved up to the north of Moscow, and then plunged back south towards Pakistan. This brought hot air north over western Russia, and stopped low pressure systems from dropping their rain on the region, where harvests normally depend on it.

Instead, that rain was carried far to the north of Moscow, and then down unusually far south into the mountains of northern Pakistan, where it combined with the usual summer monsoon in Pakistan to cause unusually intense flooding.

Having taken up such an unusual position, the jet stream just sat there, frozen in place. The weather systems causing the heatwave and the torrential rains remained in place for more than a month, continuing to contribute to the increasingly disastrous conditions.

The reasons for the unusual conditions in the jet stream aren't entirely clear although three suggestions have been made, including high sea-surface temperatures in the Mediterranean Sea, climate change and solar activity being modulated by the sun.

In the last week or so, the jet stream has begun to move and weaken again, and is heading back towards a more normal position and strength. A storm is heading towards Moscow. However, the consequences for both Russia and Pakistan are likely to last for some time.

I would get students to compare these events with others that have occured in previous years. They could produce a table outlining the causes, short and long term effect, social impacts and economic impacts.