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Science

Extreme weather: what's normal - what isn't?

When the weather goes crazy - is climate change necessarily to blame? Or can it be attributed to regular whims of nature? DW has the numbers.

2014 was a calm year - at least as far as the effects of natural disasters are concerned. When looking at the news, one may get a different impression, but the numbers speak for themselves - 7,700 people were killed in 2014 as a result of natural disasters. Compare that to the previous 10 years, where the average number was around 97,000. Over the 30 years prior to that it was 56,000.

"With all the tragedy involved in each individual case - it's good news that natural disasters have cost less human lives last year," Torsten Jeworrek says. He is a member of the board of reinsurer Munich Re.

Since the 1970s Munich Re - one of the world's leading reinsurance companies - has been gathering statistics about damage and losses caused by floods, droughts, hail, cold temperatures, tornadoes and hurricanes. Geophysical incidents, such as earthquakes, tsunamis or volcanic eruptions are also listed in the statistics.

The overall downward trend of fatalities is not purely accidental. In many places technical early warning systems function better today than they did several years ago. "Authorities have evacuated and sheltered people more systematically. For example, in the case of tropical storm Hudhud on the southern coast of India or in the case of the typhoon Hagupit that hit the Philipines," Jeworrek adds.

2014: Fewer victims, more catastrophes

Looking at the diagram below, there is a seemingly contradictory trend: The number of natural disasters has been on a constant rise since 1980. Slowly but surely, Munich Re has been registering more and more individual incidents, with 2014 reaching a high point of 980 incidents in which considerable damage was reported. In the 10 years prior to that, the annual average was 830 and over the last 30 years, it was only 640.

"One factor is certainly climate change," Stefan Straub tells DW. The expert dealing with climate change and renewable energy at Munich Re has another explanation, however: "A reason may simply be, that such events are easier to monitor and to record today," he adds.

"Individual incidents we do not attribute expressly to climate change, because each individual event is possible even without climate change," Straub explains. "But there may be events that can be aggravated by climate change - for example a high tide in combination with a severe storm and rising sea levels." After all, climate-observations are composed of aggregated weather events over a very long time period. That eventually makes cause and effect visible.

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Less geology - more weather

Last year, 92 percent of all recorded incidents of natural disasters, causing significant damage, involved extreme weather. Earthquakes, tsunamis or volcanic eruptions only played a minor role.

It should be noted, however, that the hurricane season in the Northern Atlantic was comparably mild. On the other hand, the Eastern Pacific was hit more frequently by strong storms. In most cases, however, there was no landfall.

In stark contrast to the North-Western Pacific, where numerous typhoons hit the Japanese coast. However, due to the high construction standards and the highly developed infrastructure in Japan, the damage there was minor.

Greetings from El Nino

"The patterns we observe are actually in line with what we would expect from an upcoming El Nino-phase," Peter Höppe says. At Munich Re he is in charge of research on global risks. And last December California was hit by storms and heavy rainfall, after a long drought - also an indication of that climate phenomenon.

The half-year statistic for 2015 looks more grim than last year. Within the first six months, 16,000 people died. Out of those almost 9,000 were attributed to the devastating 7.8-Richter Scale earthquake in Nepal. "Often the number of extreme weather incidents and natural disasters is random," Straub says on the difficulty predicting or explaining the changing numbers.

Then, in June 2015 there were devastating droughts in India and Pakistan, claiming 3,600 victims. While heat-spells are normal in that part of the world before the beginning of the monsoon season, it is not entirely common for the temperatures to go above 47 centigrade - aggravated by little wind and high humidity.

While these numbers are high, compared to 2014, they still look less dramatic - comparing them with the 10-year average of 46,000 fatalities in the first six month of each year.

Once El Nino has peaked and is retreating early in 2016, a La Nina phase is expected to set in, which means the overriding normal climate conditions in the Pacific region will get stronger than usual. La Nina is considered the smaller sister of El Nino.

Hard to predict

The German Weather Service (DWD) is hesitant to make long term predictions, however. "We may have observed a certain rhythm for a while, but I sense, that it has petered out," meteorologist Gerhard Lux told DW. What weather you get depends on several factors, he adds: "It is always possible, that you get a surprise. Serious weather predictions are possible over a period of only five to 10 days." Warnings are therefore only possible about one week in advance.

Florian Imbery from the department of climate analysis at DWD does not believe that individual peak weather events, such as storms, hurricanes or floods can be linked to climate change. He told DW: "We have to look at the long term."

In climate research the periods, scientists usually look at periods of at least 30 years "Then, there are three points of interest: how often does the event take place, when does it take place and how intense was it?"

How this works, he demonstrates with the example of heat spells in German cities. Since the 1990s they have occurred more often. "And this we can explain with global warming," Imbery says.

Warmer weather - more extremes

Paul Becker, vice President of the DWD stressed last March at the weather service's annual press conference that a link between more heat waves and climate change is almost certain. "And it is necessary to prepare our society for the effects of climate change."

Munich Re also comes to that conclusion, looking at the data for the first half of 2015: "The natural disasters show us, how vulnerable especially developing countries and emerging economies still are," Torsten Jeworrek says.