Two scientists from Wits University have published a paper in the International Journal of Climatology which says that South Africa may be at increased risk of tropical storm damage over the next 40 years.
Jennifer Fitchett and Prof Stefan Grab, from the Wits School of Geography, Archaeology and Environmental Science (GEAS) studied storm activity in the south-west Indian Ocean over the last 161 years. They found that contrary to popular belief, global warming isn’t causing an increase in the number of tropical storms and cyclones appearing, but it is causing extreme weather to move south.
According to Fitchett, the misconception that the number of storms is increasing may be a result of better reporting technologies – we’re seeing more activity because we’re better at looking for it.
“From 1940, there was a huge increase in observations because of aerial reconnaissance and satellite imagery,” Fitchett says in a Wits press release.
What the pair did find, however, was that storm formations were moving south. According to Fitchett, the minimum surface temperature required for tropical storms to form is 26.5 degrees Celsius – and the isotherm which marks the point where sea water reaches this temperature has been moving south at a rate of 0.6 degrees Celsius per decade since 1850. If that rate of movement continues, she says, the eastern coast of South Africa could find itself battered by frequent storms as a result of cyclones by 2050.
Fitchett points to the fact that most tropical storms develop to the north of Madagascar, but of the seven which have developed to the south of the island in the last 66 years, four were in the last two decades. When cyclones are born on the south side of Madagascar, she says, they hit Mozambique and cause heavy rains in Limpopo.
We’re just downloading the full report to have a more in-depth read of the findings.
In a second paper published, the pair also looked at the effect of climate change on citrus fruit farms in Iran, and found that fruit trees are flowering up to a month earlier than they were 50 years ago, leaving them vulnerable to late season frost.[Image – Storms off of Madagascar, NASA]