WHY IT HAPPENED:A SWITCH in temperatures in the distant waters of the Pacific may be behind the devastating rains that have lashed northwest Pakistan, scientists have said. But while consistent with climate change, the heaviest monsoon in many decades cannot be directly attributed to the warming of the planet.
The surface temperature of the oceans determines the water vapour that rises from them and this is the primary influence on the weather in the tropics.
In the last few weeks, the surface temperature in a critical part of the Pacific has flipped from being above normal to below normal, said Tim Palmer, Royal Society professor of climate physics at Oxford University. That changes the global weather pattern from the El Niño phenomenon – drier in Pakistan and India while wetter in the Americas – to the mirror-image La Niña pattern, in which the Asian monsoon becomes more intense.
“What has happened in Pakistan is consistent with that,” Prof Palmer said. Last week saw up to 500mm of rainfall in a few days on the affected areas of Pakistan, double the average for a month, and more is likely this week. – (Guardian service)