Dave, IMHO we cannot totally dismiss "Climate Change" as nonsense. There is compelling evidence to show that our climate is indeed changing. What we can debate though is the CAUSE of that change. Human or natural (whatever that means). You mentioned the desertification of the Sahara. Probably the most common theory is that the Sahara dried up due to a change in the Earth's orbit, which affects solar insolation, or the amount of electromagnetic energy the Earth receives from the Sun. In simpler terms, insolation refers to the amount of sunlight shining down on a particular area at a certain time, and depends on factors such as the geographic location, time of day, season, landscape and local weather
Around 8,000 years ago, the Earth's orbit was slightly different than it is today. The tilt changed from around 24.1 degrees to the present-day 23.5 degrees.
In addition, the Earth had its closest approach to the Sun in the northern hemisphere in August, while today, that closest approach is in January. So, summertime in the north was warmer than it is now.
The changes in the Earth's orbital tilt and precession occur because of gravitational forces emanating from other bodies in the solar system. Just like a top, the Earth wobbles slightly about its rotational axis. This tilt changes between roughly 22 and 25 degrees about every 41,000 years, while the precession varies on about a 26,000-year period. These cycles have been determined by astronomers and validated by geologists studying ocean sediment records.
From the above record, it was theorized that the Earth's tilt would change only insignificantly in the next century. However, scientists from NASA's Jet Propulsion Laboratory say that the current melting of ice in Greenland is already causing the tilt to change at a rate of approximately 2.6 centimeters each year. They predict that his change could increase in the years ahead as more ice melts.
Putting it all together, the changes in insolation caused by shifts in axial tilt have an impact on atmospheric weather patterns. Thousands of years ago when the northern hemisphere received more sunlight, it intensified the monsoons. After the Earth's tilt changed, the monsoons decreased and the vegetation began to disappear. When there were no plants to retain water and release it back into the atmosphere, the rain progressively decreased. The resulting feedback loop between plant life and climate eventually created the current desert conditions.
In 1999, German scientists used computer simulations to model the Earth's climate thousands of years ago. They concluded that the climatic transition of the Sahara took place abruptly, within a possible span of about 300 years. Given the very strong dependence of vegetation on water availability, the end of the 'Green Sahara' would have come about quite suddenly as a very slow change in the orbit led to an abrupt collapse in that ecosystem.
Bobby, Sea Level sounds like a pretty simple thing BUT it's determination is actually quite complex and is, in fact, at any location, an 'average' or mean value calculated over a period of time
The precise determination of a "mean sea level" is a difficult problem because of the many factors that affect sea level, i.e., the sea is in constant motion, affected by the tides, wind, atmospheric pressure, local gravitational differences, temperature, salinity and so forth.
To an operator of a tide gauge, MSL means the "still water level"—the level of the sea with motions such as wind and waves averaged out, i.e.: averaged over a period of time such that changes in sea level, due to the tides, also get averaged out. It is important to note that the values of MSL are made with respect to the land. Thus a change in MSL can result from a real change in sea level, or from a change in the height of the land on which the tide gauge operates.
In the UK, the Ordnance Datum (the 0 meter height on UK maps) is the mean sea level measured at Newlyn in Cornwall between 1915 and 1921. Prior to 1921, the value used was MSL at the Victoria Dock, Liverpool.
In France, the Marégraphe in Marseilles measures continuously the sea level since 1883 and offers the longest available data about the sea level. It is used for a part of continental Europe and main part of Africa as official sea level. Elsewhere in Europe measurements are made relative to the Amsterdam Pile elevation (water level in the canals of Amsterdam), which dates back to the 1690s.
Recently satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES, TOPEX/Poseidon was followed by Jason-1 in 2001 and the Ocean Surface Topography Mission on the Jason-2 satellite in 2008.
All the available data shows that for at least the last 100 years, sea level has been rising at an average rate of about 1.8 mm (0.1 in) per year. Most of this rise can be attributed to the increase in temperature of the sea and the resulting slight thermal expansion of the upper 500 meters (1,640 feet) of sea water. Additional contributions, as much as 25% of the total, come from water sources on land, such as melting snow and glaciers and extraction of groundwater for irrigation..