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2017 Was the Warmest Year for the Ocean on Record

According to a new study, human activity has caused our global ocean to warm to levels never seen on record.
A storm over the ocean.

2017 was the hottest year on record in our global ocean, according to a new study published in Advances in Atmospheric Sciences, which uses some of the most up-to-date scientific methods of measuring ocean heat.

Our oceans absorb 90 percent of the heat that humans create in the atmosphere by polluting greenhouse gases, meaning they’re one of the biggest environmental victims of global warming. This explains why even though 2017 was the second-hottest year on record in the air, 2017 was the hottest year on record in the oceans.


The study uses a new method of measuring the amount of heat in the ocean, which Cheng helped develop in 2017. It works by creating a robust grid of the global ocean, analyzing location-specific ocean temperature data, and integrating this data into a map that provide a portrait of how the ocean has changed from 1960 to now. It also accounts for short-term changes to the ocean, like El Niño and La Niña events.

According to Cheng, analyzing measurements on a micro-scale with this method helps counteract the conservative estimates, which are common in studies focused on the ocean.

“We expect there will be stronger estimates of past ocean warming trend than previous reported because we already know that many traditional methods underestimate the long-term trend,” Cheng said in an email.

Cheng told Motherboard that these ocean levels don’t just have implications for the present: since the ocean warms slowly and has a huge capacity to suck up heat from the atmosphere and store it, the ocean will continue to be warm and get warmer long into the future.

“In another word, the ocean is the memory of the past changes,” Cheng said.

Our oceans are in a dire state, and we’ve known this for years. Human pollution of greenhouse gases is warming our oceans, which is helping to driving it to levels of acidity the earth haven’t seen in 252 million years (at a time 96 percent of life on earth went extinct). Coral reef ecosystems, the backbone of many ocean ecosystems, are collapsing from the inside out. A nasty feedback loop is causing the seafloor to literally collapse and help the ocean acidity even faster. A seasonal oxygen-free “dead zone” in the Gulf of Mexico is now larger than New Jersey.

Scientists for the UN have explicitly told global governments that we have about twelve years to restructure our systems of production, transportation, and governance in order to limit the warming of the earth to somewhat livable levels. Twelve years is arguably much too optimistic. And it’s important to note that in a best case scenario, we’ll still warm the earth 50 percent more than we’ve already warmed since the nineteenth century.

But even in a best-case scenario where we fundamentally change our modes of production and limit warming to 1.5 degrees Celsius above pre-industrial levels, our oceans will continue to warm and expand for decades. Violent, climate-change driven storms will flood and destroy cities, and claim human lives.