An eternal source of wonder and awe, the world's oceans hold the key to all life on Earth, covering 70 percent of the planet, having produced in the course of history half of the world's oxygen and supplying protein for four in every ten of the world's people.
Put simply, we can't survive, any of us, without healthy oceans.
That's why the United Nations is sounding the alarm - and sounding a call to action - over the damage climate change is doing to our oceans, and the threat of even greater danger to come.
More than 90 percent of the warming caused from burning fossil fuels is absorbed by the Earth's oceans. That means the impacts we're already seeing from climate change on land - raging wildfires, widening deserts, mass extinctions, withering heat - hint at less than 10 percent of the global problem.
The rest of the story is told in a new IPCC report on how climate change is affecting our oceans and water frozen in glaciers and ice sheets, The Ocean and Cryosphere in a Changing Climate. It's a sobering and essential read that ends on a note of hope: there's still time to save the world's oceans, but no time to delay.
Our oceans, while large, are fragile. They require just the right combination of temperature, current flows, salinity levels and more to sustain the conditions that support everything from the tiniest plankton to the mightiest whale.
Climate change is already throwing that delicate balance out of whack, and we're seeing the impacts everywhere.
Chiefly by burning coal, oil and gas, we've warmed our oceans by about 1.8 degrees C°, mostly in the past several decades.
That might not sound like a lot, but it takes an enormous amount of heat to warm the ocean and subtle shifts can mean big change. As waters warm, they hold less of the oxygen marine life needs to survive - and the animals are already responding. Fish are moving toward the poles or into deeper water.
These aren't seasonal migrations. They're permanent shifts that speak to rapid change.
Warming waters are killing Australia's Great Barrier Reef and threatening coral everywhere. Often called the rainforests of the seas, coral reefs support an astonishing array of foundational marine life, the IPCC report explains, warning "Almost all warm-water coral reefs will decline," as the planet continues to warm.
Warming waters have increased both the frequency and intensity of marine heat waves, like the one that recently warmed Pacific waters by as much as 7 degrees C° above normal from the Gulf of Alaska to Baja Mexico. During that 2014-2015 heat wave, fish populations plummeted, sea birds, whales and other wildlife starved, and commercial and recreational fisheries were shut down.
Sea levels are rising, as the oceans expand with the heat and take on water from melting ice sheets and glaciers.
The IPCC report conservatively projects sea level rise up to 1.10 meters by the end of the century. That's a global estimate that could vary, up or down, by as much as a third, depending on the coast. And these estimates don't factor in new findings of how fast things are changing in the polar regions that make even higher sea levels plausible.
Some of the fastest sea level rise in the world, for example, is happening along the U.S. East Coast, where seas are rising 40 percent faster than the global average.
We've lost half the world's coastal wetlands over the past century, due to development pressures as well as climate change. By the end of this century, rising seas are going to swallow at least one-fifth, and as much as 90 percent, of what's left.
The fact is, if we don't put the brakes on global warming, rising seas will swamp coastal communities that are home to some 680 million people worldwide, the IPCC report warns, by the end of this century, if not sooner.
All of this is combining to make storms and hurricanes more devastating. As hurricanes brew over warmer waters, they take on more energy, in the form of heat, and moisture. That means that when they make landfall, they pack more of a wallop, as we've seen from monster hurricanes like Harvey, Michael, Maria and Dorian.
In addition to heat, oceans also absorb about one-third of the additional carbon pollution from burning fossil fuels. That's upsetting the chemical balance of our ocean waters, making them increasingly acidic, to the further detriment of corals, clams, shrimp and other marine life.
Ocean ecosystems are complex, but the story here is simple.
We won't survive without healthy oceans. We can't afford to choke the life out of the seas and let them become marine deserts as a sacrifice to our addiction to fossil fuels. The IPCC. report charts a better way forward.
It starts by cutting fossil fuel use around the world, by investing in renewable energy and energy efficiency, so we do more with less waste; shifting to all electric and hybrid vehicles; and getting more clean power from the wind, sun and water.
It means strengthening the health of our oceans to make them more resilient to climate impacts by, for example, ending the atrocity of dumping nearly 22,000 tons of plastic into the world's oceans each day.
And it means preparing our coastal communities for the climate impacts we're already experiencing or are certain to experience soon, and providing additional help for low-income people and others who lack the wherewithal to move themselves out of harm's way.
None of us wants to imagine a world without healthy oceans. The IPCC report makes clear that's where we're headed, though, unless we change course, and fast. It's a foghorn blasting through the cloud of confusion and lies from those who don't want us to change.
Let's listen to the scientists. Let's heed the warning they sound. Let's do our part to avert climate catastrophe, before it's too late to act.
Any views expressed in this opinion piece are those of the author and not of Thomson Reuters Foundation.