Drought in the basin of the Missouri river at the turn of XX and XXI centuries were the most devastating in the last 1200 years, which underscores the human influence on them. To such conclusions scientists have come, having paleo-climatic analysis of annual rings of trees growing on the catchment area. In an article published in the journal Proceedings of the National Academy of Sciences, also refers to future anthropogenic climate change on drought and the rivers in the Western United States.
US West is one of the regions where water demand exceeds the inventory in the ecosystem, and not the last cause of this problem is drought. It is known that the extreme heat at the turn of XX and XXI centuries has depleted the basin of the Colorado river, and her fate repeated some smaller rivers.
A similar phenomenon took place on the territory of and countries of the former USSR: if America to serious consequences for the economy and the environment resulted in the dust bowl, we have a similar situation has arisen through 30 years with the development of virgin lands. In addition, the extensive use of waters of Amudarya and Syrdarya has led to the almost complete disappearance of the Aral sea. Currently, the lower reaches of the Volga and don rivers that receive mostly snow power, also suffer from prolonged droughts because of higher air temperature and operation of the hydroelectric system, therefore, the study of droughts in basins of major rivers is an important issue related to various regions of the world.
Still remained unexplored influence of droughts on the condition of the Missouri river — the largest waterway of the United States. The period of instrumental observations of the nutrition of the American rivers covers the whole XX century, but in order to assess how much destructive are the drought of recent years in a historical context, it is necessary to understand their development over a much longer period.
Scientists under the leadership of Justin Martin (Justin T. Martin) from the University of Arizona decided to find out whether the recent drought in the basin of the Missouri river in recent years in a cycle of natural variability, or increasing anthropogenic impact makes it more strong and long lasting. For this, the researchers have used project data PAGES2k, which include the annual change in the width of annual rings and wood density of ancient trees in the Western United States. These indicators allow to draw conclusions about the air temperature and atmospheric precipitation during the life of the tree. Information about the XX and XXI century were taken from direct observations (projects PRISM and CLIMDIV).