February 25, 2014
South African Researchers Debunk Two Climate Change Theories
Brett Smith for redOrbit.com - Your Universe Online
A new study from South African researchers has debunked the notion that there are more tropical cyclones taking place due to global warming – at least in the Southern Indian Ocean.
Jennifer Fitchett, a PhD student at Witwatersrand University in Johannesburg, said better meteorology has probably fueled the idea of climate change developing more and more storms.
“From 1940, there was a huge increase in observations because of aerial reconnaissance and satellite imagery,” she said.
According to the report, co-authored by Fitchett and published in the International Journal of Climatology, tropical storms hitting the southeastern coast of Africa may not be increasing in number – but they are shifting south due to increasingly warmer temperatures on the surface of the sea.
For the study, the researchers used data from three storm track records that spanned periods between 66 and 161 years and discovered that there has been no rise in the amount of tropical cyclones. However, when the study team looked at where storms have been taking place, they found that the 80-degree surface temperatures needed for a cyclone to occur have been moving southward toward the pole. This phenomenon has coincided with storms shifting farther to the south.
Most cyclones strike Madagascar and don’t continue on to Mozambique, and those that strike Mozambique form to the north of Madagascar. However, in the past 66 years there have been seven heavy storms which have formed south of Madagascar and hit Mozambique directly. The study researchers noted that a high number of them have transpired in the past 20 years.
“This definitely looks like the start of a trend,” Fitchett said.
Fitchett warned that the latitudinal line of 80-degree surface water, called the isotherm, has been moving south at a rate of 0.6 degrees per decade since 1850.
“At current rates we could see frequent serious damage in South Africa by 2050,” she said. “This is not what we expected from climate change. We thought tropical cyclones might increase in number but we never expected them to move.”
Fitchett has also co-authored another recently released study that counters a prevailing notion about climate change – the idea that the last days of frost-creating conditions in late winter have been creeping back toward the start of the year.
In that study, which was published in the International Journal of Biometeorology, the researchers noted that changes in late-winter frost are not happening as quickly as changes in the flowering of fruit trees in Iran – occurring as much as a month earlier than they were 50 years ago.
“The layman’s assumption is that as temperatures get warmer, there will be less frost,” Fitchett said. “But although the severity of the frost has decreased, the last day of frost hasn’t been receding as quickly as the advances in flowering. The result is that frost events are increasingly taking place during flowering and damaging the flowers. No flowers equals no fruit.”
The researchers looked at data on oranges, lemons and tangerines in two cities in Iran and concluded that in the city of Kerman, frost will form during peak flowering in approximately 70 years.
“Iran is a top citrus producer but they don’t export and we don't yet have data on whether there has been an impact on their citrus yields. We think that if there hasn’t already been a huge impact, there soon will be,” Fitchett said.