Atmospheric Warming Intensifies Earth’s Water Cycle
Australian scientists from the Lawrence Livermore National Laboratory in California and the Commonwealth Scientific and Industrial Research Organization (CSIRO) report that in the last fifty years, salinity levels in the world’s oceans have shifted and that climate change is affecting global rainfall and evaporation cycles.
According to the lead author of the study, Dr. Paul Durack, researchers looked at the correlations between salinity, rainfall, and evaporation in climate models and at salinity variations within the ocean. They conducted the study from 1950 to 2000, during which time they found that the water cycle has increased by 4% – twice the reaction that current global climate models have predicted.
“Salinity shifts in the ocean confirm climate and the global water cycle have changed.” Dr. Durack also discovered “…robust evidence of an intensified global water cycle at a rate of about eight per cent per degree of surface warming.”
Dr. Durack, a post-doctoral fellow at the Lawrence Livermore National Laboratory, stated, “These changes suggest that arid regions have become drier and high rainfall regions have become wetter in response to observed global warming.”
Dr. Durack observed that the patterns are not constant. Local shifts follow the ‘rich get richer’ idea, leading to drier areas to become drier and wetter areas more wet.
According to Durack, the availability of freshwater affected by climate change creates more dangers for human civilizations and ecosystems than global warming alone. Durack stated, “Changes to the global water cycle and the corresponding redistribution of rainfall will affect food availability, stability, access and utilization.”
Although it has been difficult for scientists to discover clear estimates of water cycle changes from land based testing due to a lack of data pertaining to rainfall and evaporation on the surface of the earth, they have concluded that with an estimated temperature rise of 37.4 degrees Fahrenheit by the end of the century, an increase of 24% of the water cycle is possible. According to the team of scientists, global oceans can provide a better picture of shifts within the water cycle.
Dr. Richard Matear of CSIRO’s Wealth from Oceans Flagship and co-author of the study stated, “The ocean matters to climate – it stores 97 per cent of the world’s water; receives 80 per cent of the all surface rainfall and; it has absorbed 90 per cent of the Earth’s energy increase associated with past atmospheric warming. Warming of the Earth’s surface and lower atmosphere is expected to strengthen the water cycle largely driven by the ability of warmer air to hold and redistribute more moisture.”
According to Matear, the strengthening is an increase within the patterns of exchange between rainfall and evaporation. Ocean’s comprise nearly 71% of the earth’s surface, and salinity patterns are a clear demonstration of climate shifts around the world.
According to one co-author and co-Chair of the global Argo project, Dr. Susan Wijffels, maintenance of the current fleet of 3,500 profilers is vital to further study of shifts in salinity levels in the upper oceans of the world.
The Australian Climate Change Science Program, a joint initiative of the Department of Climate Change and Energy Efficiency, the Bureau of Meteorology and CSIRO, funded the study. Dr. Durack, the lead author of the study and graduate of the CSIRO-University of Tasmania Quantitative Marine Science program, received additional funding from CSIRO’s Wealth from Oceans Flagship. The U.S. Department of Energy, under contract DE-AC52-07NA27344, supports the work carried out at Lawrence Livermore National Laboratory.
The researchers have published their study in the journal Science.