ACCORDING to research led by The University of Texas at Austin, seasonal rainfall is expected to rise significantly in East Africa over the next few decades in response to increased greenhouse gases.
The study, published in July in Climate Dynamics, used high-resolution simulations to find that the amount of precipitation during the rainy season known as the "short rains" could double by the end of the century, continuing a trend that has already been observed in recent years.
The season known as the "long rains" on the other hand, is expected to remain stable according to the new projections. These results are in contrast to previous analyses that associated global warming with drier conditions that occurred earlier this century.
"There are two East African rainy seasons with different sensitivities to greenhouse gases," said Kerry Cook, a professor in the Jackson School of Geosciences' Department of Geological Sciences. "Our paper shows that the short rains will continue to increase - in fact, flooding and locust infestations are already occurring - and that there is no drying trend for the long rains."
Both the transportation of water vapor by atmospheric circulation and the distribution of rain are sensitive to differences between ocean and land temperatures. These differences occur because oceans warm and cool more slowly than the land due to differences in heat capacity.
When the short rains develop, typically with a peak in November, the southern hemisphere circulation is in a summer pattern, with high pressure over the ocean and low pressure over land in the subtropics, setting up a circulation pattern that funnels more moisture over East Africa.
It is this rainy season that is more sensitive to greenhouse-gas induced climate change. The region's long rains, on the other hand, appear to be less sensitive to greenhouse gas forcing. This season occurs from March through May, peaking near the northern hemisphere's spring equinox, when continental low pressures are centered over the equator.
The newly published simulations have a 30km resolution that resolves the complex East African topography, and more accurately represent currently observed rainfall amounts and seasonality than coarser resolution global models.
Simulations of rainfall through 2050 are consistent with currently observed rainfall amounts and seasonality. These results show that the pattern of the long rains is not changing. But the short rains are increasing: rainfall in November over East Africa will increase by about one-third by 2050 and double by 2100.
"This research will allow people to plan ahead in East Africa," said Cook. "But future work will need to see how additional rainfall will be delivered because, if it is as intense as in the current observations and continues to impact agriculture, developing infrastructure will be important."
In another development, radiocarbon dating is set to become more accurate than ever after an international team of scientists improved the technique for assessing the age of historical objects.
The team of researchers at the Universities of Sheffield, Belfast, Bristol, Glasgow, Oxford, St Andrews and Historic England, plus international colleagues, used measurements from almost 15,000 samples from objects dating back as far as 60,000 years ago, as part of a seven-year project.
They used the measurements to create new international radiocarbon calibration (IntCal) curves, which are fundamental across the scientific spectrum for accurately dating artefacts and making predictions about the future.
Radiocarbon dating is vital to fields such as archaeology and geoscience to date everything from the oldest modern human bones to historic climate patterns.
Archaeologists can use that knowledge to restore historic monuments or study the demise of the Neanderthals, while geoscientists on the Intergovernmental Panel on Climate Change (IPCC), rely upon the curves to find out about what the climate was like in the past to better understand and prepare for future changes.
Prof Paula Reimer, from Queen's University Belfast and head of the IntCal project, said: "Radiocarbon dating has revolutionised the field of archaeology and environmental science. As we improve the calibration curve, we learn more about our history. The IntCal calibration curves are key to helping answer big questions about the environment and our place within it."
The team of researchers have developed three curves dependent upon where the object to be dated is found. The new curves, to be published in Radiocarbon, are IntCal20 for the Northern Hemisphere, SHCal20 for the Southern Hemisphere, and Marine20 for the world's oceans.
Dr Tim Heaton, from the University of Sheffield and lead author on the Marine20 curve, said: "This is a very exciting time to be working in radiocarbon. Developments in the field have made it possible to truly advance our understanding. I look forward to seeing what new insights into our past these recalculated radiocarbon timescales provide."
The previous radiocarbon calibration curves developed over the past 50 years, were heavily reliant upon measurements taken from chunks of wood covering 10 to 20 years big enough to be tested for radiocarbon.
Advances in radiocarbon testing mean the updated curves instead use tiny samples, such as tree-rings covering just single years, that provide previously impossible precision and detail in the new calibration curves.
Additionally, improvements in understanding of the carbon cycle have meant the curves have now been extended all the way to the limit of the radiocarbon technique 55,000 years ago.
