NASA has released a new video that shows what the planet's surface would look like without water.
The animation, which is an updated version of a 2008 video, slowly drains the oceans, showing what the terrain looks like underneath.
The video gives a sense of just how complex the landscape underneath the ocean really is. The continental shelf drops become visible in the first few seconds, followed shortly after by the midocean ridges — massive undersea mountain ranges formed where tectonic plates run together. The video also shows just how deep the oceans go, with the barely visible depths of the Mariana trench draining long after the rest of the water has gone.
While the oceans aren't in danger of drying out in the near future, the animation is reminiscent of what the Earth may eventually look like, if CO2 levels continue to rise. High atmospheric CO2 in the range of 4,500 to 6,000 parts per million could lead to the evaporation of the Earth's ocean over time. In addition, it highlights more immediate threats, like the real-life water crises that are happening right now.
Water depletion around the globe
While sea levels are expected to rise as climate change melts ice and permafrost, inland bodies of water may not be so lucky.
Scientists recently determined that increased temperatures, caused by climate change, are behind the current sea-level drop in the Caspian Sea, the world's largest inland body of water. They believe the higher temperatures are causing elevated evaporation of surface water, leading to the sea's shrinkage. The water loss is likely to continue as long as temperatures rise, and could soon pose a serious threat to the highly biodiverse Caspian Sea ecosystem.
If left unchecked, the evaporation may eventually lead the Caspian to face a fate similar to that of the Aral Sea, another massive body of water — an inland lake, despite its name — in the same region. In the past few decades, the Aral has gone from being the fourth-largest lake in the world to a fraction of its size. This was due to water mismanagement in the Soviet Union. Bad water policy and increased evaporation as the result of climate change continue to shrink the lake today.
Climate change-related water loss is likely to impact most sources of water around the globe as well, though the changes may not be as pronounced as those seen in large bodies of water like the Caspian and Aral. According to the World Resources Institute, 17 countries, which together contain more than a quarter of the world's population, are expected to face extremely high water stress within the next 20 years.
Major water crises may come even sooner, as well. In 2018, Cape Town, South Africa, nearly faced its "day zero"— the day when the city's water supplies were set to run totally dry. The crisis was averted, but only temporarily. The risk of water scarcity remains high both in the city and the rest of the country.
Other major cities — including Tokyo, Mexico City, London and Los Angeles — may soon face similar crises. Temperatures are rising and demand for water continues to increase. At the same time, water scarcity in major cities may be made even worse by pollution, which contaminates our oceans and sources of drinkable water with pollutants like plastics.
The growing scarcity of water will likely be the worst in areas that are already struggling with water supplies, as well as rural or undeveloped areas where infrastructure is limited. However, even developed regions won't necessarily be immune to growing worldwide water scarcity. By 2040, it is predicted that nearly a quarter of the U.S. will experience "extremely high" water stress.
This scarcity isn't guaranteed, of course. Better water management and action against climate change could turn those trends around, and significantly reduce the risk of high water stress over the next few decades.
The future of our planet's water
While the oceans aren't expected to dry out any time soon, water scarcity will likely become one of the most pressing issues over the next few decades.
Water loss is already reshaping the face of our planet — shrinking the boundaries of major bodies of water like the Caspian Sea — and will likely have significant impacts just about everywhere.