The first global comparison of coastal sediments allowed to determine the long-term cyclic changes in tropical cyclone activity.
Cycles were too large, and therefore they can not be found in the historical sources. Some areas that are now considered safe in the past been the strongest storms in the future again feel the power of nature.
History tells us that the number of tropical storms in the North Atlantic and the Pacific increased and decreased for several decades, but the data we have covered only 100-150 years. In search of long-term cycles, the researchers turned to the fossil record. Ancient storms can be detected by namyvaniyu sand lagoons or create ridges on the low-lying coast.
Jonathan Nott and Anthony Forsyth from James Cook University (Australia) were the first who succeeded global analysis. They collected data for about six thousand years, that is from the time when the world's oceans has reached the current level. The researchers summarized the results of dozens of studies conducted in Australia, North America, Japan and Puerto Rico.
Everywhere tropical storm has had its ups and downs, covering hundreds of years. The reason for such cycles remains unclear. Indirect evidence suggests a connection with the Southern Oscillation in the Pacific Ocean because of showing a picture of a similar storm similar ways to respond to phase Southern Oscillation. Thus, El Niño, apparently associated with increased storm activity in Western Australia and southern Japan and its decline in North America and eastern Australia. Alas, paleoclimatic data are not sufficient to establish the truth.
The most important thing is that the findings of researchers have questioned the local risk assessment. For example, last year a very severe cyclone hit the north-east Queensland — the first time in the history of meteorological observations for the area, which were conducted in 1870. However, the geological record shows that in the past it was common.
The study is published in the journal Geophysical Research Letters.
Prepared according to NewScientist.