Central Asia is characterised by an arid and continental climate. This means that summers are very hot (up to 50°C in the deserts), winters are very cold (down to -60°C in the high mountain areas of the Pamirs in Eastern Tajikistan) and precipitation is very low. Over the last few decades, global warming has led to an increase in the surface temperature in Central Asia. The map below shows that increase per decade.
The map shows that the increase in temperature differs by region. It also differs depending on the season. In general, climate warming in the winter months is stronger than in other seasons. However, peak temperatures in summer have also been rising. Since the 1950s, the number of days with temperatures above 40°C has been increasing in the southern areas of Central Asia. Climate change scenarios for Central Asia forecast a 1° to 3°C increase in temperature by 2030–50. By the end of the century, temperatures could increase by up to 6°C if emissions are unmitigated and greenhouse gas continues to accumulate.
Climate change will have a huge impact on water security. Future increases in both rainfall variability and extreme weather events will make water availability less predictable while raising temperatures increase water demand. Climate change has also altered precipitation patterns. As the map shows, it caused more precipitation in northern parts of Central Asia and less in the south, where most agricultural areas are. But the most disturbing effect of global warming in Central Asia is the melting of glaciers. Since about 1950, between 14% and 30% of the Tian Shan and Pamir glaciers have melted. Today's rate of glacier loss in Central Asia is 0.2–1% per year. Some of the small glaciers (smaller than 0.5 km²) have already totally melted.
Connected with this process is the danger of so-called Glacial Lake Outburst Floods (GLOFs), which happen when water dammed by a glacier is released. Due to glacial retreat, the number of glacial lakes and incidences of failure has been increasing globally over the last 40 years. This danger is also acute in Central Asia. Scientists warn that in Kyrgyzstan alone, more than 20 glacial lakes are in danger of outburst.
Glacial retreat has a strong impact on water availability in the rivers in Central Asia. Meltwater from snow, glaciers and permafrost supplies around 80% of the total river runoff in Central Asia. Glaciers are therefore a crucial source of water for irrigation agriculture as well as for hydropower production.
In the short term, discharge in some glacier-fed rivers is expected to continue to increase slightly during the summer months due to the intensified glacier and permafrost melting. In the long term, however, discharge will decrease and some glaciers will disappear. Experts estimate that the flow of the Amu Darya might be reduced by 7% to 15% by 2050, and the Syr Darya by 5%, as a result of the loss of glaciers and permafrost, higher temperatures, increased evaporation and reduced surface runoff. In smaller rivers fed by small glaciers, this reduction will be much more substantial, even leading to total drying-up within a few decades. In the decades leading up to 2100, this reduction is expected to be even higher as the figure above shows. But even a small reduction can have disastrous effects in those downstream areas that are already facing shortages today. Therefore, Central Asian water managers have to expect serious water deficits in the coming decades.
This is exacerbated by the fact that the demand for water will increase due to population growth, higher temperatures and a decrease in precipitation in some parts of Central Asia.
This also has implications for transboundary cooperation. The principal difficulty-unstable river regimes that would require constant planning and re-negotiation of water releases-grows with climate change as flow variation increases. Hence, climate change makes transboundary cooperation even more difficult. Flexible institutions for adaptive management are paramount and institutional strengthening is critical.[EDB 2009, ZOI 2009]