The Caspian Sea, like the Aral Sea, Black Sea, Lake Urmia, and Lake Van, is a remnant of the ancient Paratethys Sea. It became landlocked about 5.5 million years ago due to tectonic uplift and a fall in sea level. During warm and dry climatic periods, the landlocked sea almost dried up, depositing evaporitic sediments like halite that were covered by wind-blown deposits and were sealed off as an evaporate sink when cool, wet climates refilled the basin. One of the most vulnerable ecosystems to climate change is the enclosed and inland seas.
The climate change trends observed in these waters are generally more complex than that characteristic for the open ocean. The Caspian Sea is the largest enclosed inland body of water on earth by area, variously classed as the world's largest lake or a full-fledged sea. It is in an endorheic basin (it has no outflows) and located between Europe and Asia. It is bounded to the northeast by Kazakhstan, to the northwest by Russia, to the west by Azerbaijan, to the south by , and to the southeast by Turkmenistan. It is now -28 m below the normal sea level.
Due to the current inflow of fresh water, the Caspian Sea is a freshwater lake in its northern portions. It is more saline on the Iranian shore, where the catchment basin contributes little flow. Currently, the mean salinity of the Caspian is one third that of the earth's oceans. The Karabogazgöl embayment, which dried up when water flow from the main body of the Caspian was blocked in the 1980s but has since been restored, routinely exceeds oceanic salinity by a factor of 10.
The Aral Sea was an endorheic lake lying between Kazakhstan ( Aktobe and Kyzylorda provinces) in the north and Uzbekistan ( Karakalpakstan autonomous region) in the south. The name roughly translates as "Sea of Islands", referring to over 1,100 islands that once dotted its waters; in Old Turkic Aral means "island". The Aral Sea drainage basin encompasses Uzbekistan and parts of Tajikistan, Turkmenistan, Kyrgyzstan and Kazakhstan. The shrinking of the Aral Sea has been called "one of the planet's worst environmental disasters". The region's once-prosperous fishing industry has been essentially destroyed, bringing unemployment and economic hardship. The Aral Sea region is also heavily polluted, with consequential serious public health problems. The departure of the sea has reportedly also caused local climate change, with summers becoming hotter and drier, and winters colder and longer.
In the late 1990s, Lake Urmia, in north-western Iran, was twice as large as Luxembourg and the largest salt-water lake in the Middle East. Since then it has shrunk substantially, and was sliced in half in 2008, with consequences uncertain to this day, by a 15-km causeway designed to shorten the travel time between the cities of Urmia and Tabriz. Historically, the lake attracted migratory birds including flamingos, pelicans, ducks and egrets. It’s drying up, or desiccation, is undermining the local food web, especially by destroying one of the world’s largest natural habitats of the brine shrimp Artemia, a hardy species that can tolerate salinity levels of 340 grams per litre, more than eight times saltier than ocean water. Desiccation will increase the frequency of salt storms that sweep across the exposed lakebed, diminishing the productivity of surrounding agricultural lands and encouraging farmers to move away. Poor air, land, and water quality all have serious health effects including respiratory and eye diseases.
As a starting point of the proposed Project by the Riparian Countries of the Caspian Sea on a theme of “Dynamics of the Caspian Sea Water Level Fluctuations During Holocene Until the Present Affected by the Climate Change: Impact on the Ecology and Socio-Economics of the Region”, the aim is to increase the exchange of the international scientific cooperation on Caspian Sea, Aral Sea, and Urmia and Van lakes. This International Conference “International Conference - Understanding the Problems of Inland Waters: Case Study for the Caspian Basin” will take place in Baku during 12-14 May 2018.