Without oceans, rain would be rare. Without rain, Earth would become one huge desert. John Kershner/Hemera/Thinkstock
The good news: We wouldn't have time to miss the dolphins. The bad news: We'd be too busy dealing with everything in the world being on fire. It's a situation that would make it hard to focus on anything else.
The oceans are the most important support system for life on Earth — maybe even necessary for evolution on any planet in the first place [source: Cullum].
Oceans basically have two life-supporting roles. First, they absorb and distribute solar radiation. Without water, harsh rays from the sun would bake the equator while distributing almost no energy to the poles, especially in the winter. Fortunately for us, water does a great job of absorbing energy, and the oceans regulate temperatures around the Earth. Currents circulate warm tropical waters to the north and south and cold water back to the equator, distributing heat energy so that no place gets too hot for life to survive and warming colder areas. Second, the oceans feed the water cycle — the movement of water from the seas to the air to the clouds, across miles and back again to the sea or to fall on land.
When water is heated at the equator, it evaporates and becomes clouds. As warm air rises, it also draws in cooler air from underneath. This process stimulates more even heat distribution, turning places where it would otherwise be too cold to live into lush, balmy gardens. That's why the Mediterranean is so temperate and why there are places in Scotland, warmed by the Gulf Stream, where you can grow palm trees.
But let's get back to what would happen if the oceans were gone. In this scenario, we're going to say the oceans have turned to dirt. We'd like to give ourselves a small window of survivability, so let's say the dirt is moist enough that it won't immediately turn the planet into an enormous dust storm.
The oceans are gone, but we still have some water. Let's take stock. Ice caps, lakes and rivers (which now flow to vast expanses of soil) and underground water are still available. Added together, those sources total about 3.5 percent of our present water supply, the other 96.5 percent having disappeared with the oceans. That's not enough to get a decent worldwide water cycle going, even if we melted the ice caps. (About 68.7 percent of Earth's fresh water is frozen in glaciers, ice caps and permanent snow, mostly in Antarctica [source: USGS].) Without clouds forming over the ocean, rain would be incredibly rare, and the planet would become desert. We'd watch our lakes and water supplies dwindle a little more every year until nothing was left.
Humans might survive for a while near our homes. We still would have access to groundwater and might get some underground hydroponic farms working. But on the surface, plants and animals would begin to dry out immediately. While trees can survive for a while without water, eventually everything would become so dry that fires would span the continents. This would be a multifaceted problem for humans: Aside from the usual problems associated with fire (such as burning to death), the blazes would release tons of carbon dioxide into the progressively stifling atmosphere, accelerating global warming.
The sun would continue to pound the equator, turning it into a furnace with no relief from circulating ocean currents. Meanwhile greenhouse gases from the world's fires would trap the sun's energy close to the ground. Some difference in temperature between night and day would create high- and low-pressure systems and produce wind, but the average temperature on Earth would be 153 degrees Fahrenheit, making surface life impossible for even the hardiest desert animals [source: Philander].
People would have to move. Humanity's only hope would be the window when the Antarctic ice sheet was still intact, prompting massive migrations to the Southern Hemisphere. As temperatures across the globe rose and Earth's surface became uninhabitable, all of our energy would go toward collecting Antarctic ice underground, where it would be safe from evaporation. We might try to build some kind of self-sustaining biosphere underground, but Antarctica's remoteness would make it difficult. Just gettingthere would be hard enough. And survivors would find a flooded wasteland and no infrastructure or resources — no mines, no roads, no food. It's unlikely enough people would survive to finish the project. The few remaining stragglers would dwell in underground bunkers.
Things would get worse. On the planet's surface, all plant life is gone. As the world burned, the atmosphere would become less and less oxygenated, perhaps becoming unbreathable for humans, even if they could somehow tolerate the extreme surface temperatures. The land would fry.
Assuming humans could survive much longer in our Antarctic bunkers, there would be no way to restart a healthy carbon cycle or bring temperatures back down to reasonable, livable levels. As humans ran out of the scant resources we'd packed along to Antarctica, we'd die off. Earth's only survivors would be small colonies of chemosynthetic bacteria hidden underground in hot springs. Without oceans, everyone else dies.