Extreme Weather Events - IELTS Listening Answers & Explanations

Good afternoon. I am Stefan Rahmstorf, a professor of Physics of the Oceans at Potsdam University. Today I'd like to talk about the extreme weather events in recent years. During the last ten years a number of stunning extreme weather events have taken place. In 2003, the most severe heat wave which broke previous temperature records and caused 70,000 deaths in Europe. Two years later, the most severe hurricane season ever witnessed in the Atlantic destroyed New Orleans and broke records in terms of the number and intensity of storms. In 2007, unprecedented wildfires raged across Greece, nearly devastating the ancient site of Olympia. In the Arctic the north-west passage became ice-free for the first time in our living memory. After record-breaking drought and heat, in 2009 over a hundred people were killed in bush fires in Australia.

There are lots of extreme weather events in 2010. For example that summer central Russia had been in the grips of its worst ever heat wave, which has caused nearly thousands of deaths. Owing to drought and heat, more than 500 wildfires had raged out of control, smothering Moscow in smoke and threatening several nuclear facilities. Another result by heat wave was the soaring grain prices since Russian government has banned wheat exports. In 2010, flooding had seemed to be a main actor in the world. In China, flash floods had killed more than a thousand people and destroyed more than a million buildings. Meanwhile, Pakistan was struggling with unprecedented flooding which has killed more than a thousand people and affected millions more. On a smaller scale, the European countries such as Germany, Poland, and the Czech Republic have also suffered serious flooding. At the same time global temperatures in recent years have been at their highest levels in records that go back 130 years. Sea-ice cover in the Arctic got to its lowest point the recorded average level for the month of June ever. Two huge chunks of ice broke off in July and August in Greenland.

Are these events connected? Does this have anything to do with global warming and are human activities to blame? Although we cannot scientifically prove or disprove that global warming caused any particular extreme events we can say that global warming very likely makes many kinds of extreme weather both more frequent and more severe. All weather is driven by energy, and the sun ultimately supplies this energy. But the biggest change in Earth's energy budget by far over the past hundred years is due to the accumulation in our atmosphere of greenhouse gases, which limit the exit of heat into space. As a result of fossil-fuel emissions, there is now one-third more carbon dioxide in the atmosphere than at any time in at least a million years, as the latest ice drilling in Antarctica has revealed.

The changes in the earth energy budget caused by solar variations are at least ten times smaller in comparison. And these changes go in the wrong direction: in recent years, the sun has been at its dimmest according to satellite measurements since 1970s. Therefore, when unprecedented extreme weather events occur, the prime suspect is naturally the biggest atmospheric change that has happened over the past hundred years - one that has been caused by human emission.

It is not difficult to understand the fact that heat waves like the one in Russia become more frequent and extreme in a warmer world. Extreme rainfall events will also become more frequent and intense in a warmer climate. According to a simple fact of physics, as usual, warm air can hold more moisture. For each degree Celsius of warming, 7% more water is available to rain down from saturated air masses. And the warming climate can also be a factor of drought risk, even where rainfall does not fall but increased evaporation rate dries out the soils.

One pattern can change atmospheric circulation is the carbon-dioxide effect which can cause more extremes of heat, drought, or rainfall in some regions, while reducing them in others. The problem is that a decrease in those extremes to which human are already well adapted supplies only modest advantages, whereas the new extremes to which we are not adapted can be devastating, as extreme events in recent years show. The extreme events in this summer indicate how vulnerable our societies are to weather-related extremes. These conditions of global warming occur after 0.8°C change. With swift and efficient decisive action, we can still limit global warming to a total of 2°C or a bit less. But even that much warming would need a lot of effort to adapt to weather extremes and even rising sea levels.

With weak action and results, like those promised by governments in Copenhagen conference in 2009, we will be on a course to 3-4°C change of global warming. Many societies and ecosystems do not adapt to the warming. If we do nothing the earth could even heat up by 5-7°C by the end of this century and more thereafter.

We have to face the facts: our emissions of greenhouse gases probably are at least mainly to blame for this summer of extremes. We do really hope that extreme weather events in this summer are a last-minute wake-up call to policy makers, the corporate world, and all citizens.