"The earliest evidence of routine hydrological observations was the regular horizontal engravings on a stone wall on an island at Aswan in the Nile River, used for measuring water levels," says Prof Alexander.
"By the time Joseph made his Biblical prophecy, it’s almost certain the sequences of good years followed by drought years were well known. And these are linked to corresponding changes in solar activity." Dr Anthony Turton recently warned that South Africa’s water crisis could be worsened by a combination of a sunspot maximum and the mother of all El Ninos in 2012/13.The World Meteorological Organisation says the output of the sun constantly varies.
A factor affecting this output is the regular fluctuation in the number of sunspots, which show up as small dark regions on the solar disk. Output peaks when the sunspot number is high. Other forms of solar activity include changes in the solar magnetic field, which influence the number of cosmic rays entering earth’s atmosphere, and variations in ultraviolet radiation that may lead to photochemical changes in the upper atmosphere. All these can affect climate.
Solar minimum and solar maximum
NASA explains that the full solar cycle, normally 11 years long, is marked by two extremes – solar minimum and solar maximum. During the solar minimum, sunspots can disappear for days at a time. When spots begin to appear again, the sun heads into a new season of extreme solar activity. At the cycle’s peak, the sun is continually peppered with spots, solar flares erupt and the sun hurls billion-ton clouds of electrified gas into space.
Violent solar events, like flares and coronal mass ejections, are the hurricanes of space. These solar storms can wreak havoc with satellites, power grids, and radio communication, including the global positioning system. Sunspot activity hit its most recent low in 2008/9, when the phenomena almost vanished for a while – as happened in 1913 when no sunspots were observed for a whole month.
The solar minimum usually lasts about 16 months. Sunspot watchers are waiting to see how quickly the cycle returns. Long periods of low sunspot numbers have been connected to global cooling. One is believed to have occurred during the Little Ice Age, between 1645 and 1715. Evidence also suggests the cold climate of 1912 may have been due to a lower level of solar energy reaching earth.
The resulting changes in sea currents and wind directions took large icebergs far south of Greenland into the shipping lanes of the North Atlantic. Since then, increases in average global temperature caused by human activity have reduced the number of icebergs in that region.
But it’s been suggested that one-third of global warming may be caused by solar energy.Certainly, changes in the distribution and amount of sunlight reaching earth played a role in the last major Ice Age. The planet was about 6Â°C cooler than it is today, and large parts of Canada and Siberia were covered by sheets of ice up to 3km thick.
Some experts say that it stands to reason that the higher energy output heralded by increased sunspot activity will result in hotter conditions and worse droughts.The National Oceanic and Atmospheric Administration, a scientific agency within the US Department of Commerce, is combining research and an operational Space Weather Centre to monitor solar activity and its effects on the planet.