3 reports sound alarm on warming oceans

The climate science printing press has been working overtime the past two weeks spitting out study after study. Even for a discipline used to eye-opening research, the recent revelations have been particularly alarming, and for scientists like myself, they deserve a big neon sign on Broadway.

In climate circles, what really sounded the sirens recently were three separate reports that show the oceans are warming at a staggering rate. 

One study published in the scientific journal Nature concludes that the oceans are absorbing 60 percent more heat than previous estimates from the U.N.'s International Panel on Climate Change. The study calculates that over the past 25 years, the oceans gained energy equivalent to more than 5 billion Hiroshima-sized atomic bombs. 

"What makes the result robust is that it actually agrees with the top of the range estimates based on temperature, which is indeed 60 percent higher than what IPCC published," said the lead author of the study, Laure Resplandy of Princeton University.

It should be noted that the methods used in the study are novel, prompting some caution from the scientific community. Experts at Climate Feedback, a global network of scientists, reviewed an article written on the paper. They said the "the study's conclusions (and implications) require additional investigation."

Dr. Kevin Trenberth of the University Corporation for Atmospheric Research (UCAR) in Boulder, Colorado, has researched extensively on ocean heat. He was not involved in the study and has questions about some of its assertions, but said "the results are quite compatible with our estimates for the most part. They have implications because the planet is clearly warming at faster rates than previously appreciated."

Any previously unaccounted for heat in the oceans is significant. One unit of water holds four times the amount of heat that one unit of air holds. You can think of the oceans as our climate control, sucking up heat and keeping our daily air temperatures moderated. In fact, more than 90 percent of heat trapped by greenhouse gases is eventually stored in our oceans, according to the National Oceanic and Atmospheric Administration (NOAA). That stored ocean heat is called ocean heat content (OHC).

That leads us to a lesser-circulated report from Zeke Hausfather of Carbon Brief, a U.K.-based website covering issues related to climate. In his report on the website, Hausfather said ocean heat content just set a new record in 2018, and the year is not yet over. This is not surprising. New OHC records are set every year because the heat keeps accumulating.

That makes the ocean a better gauge in measuring global warming trends than the atmosphere, which warms and cools more erratically. There is a very stable overall trend in the oceans.

But where does all the heat go? Some of it stays in the upper layer of the oceans, making it the heat that comes back to haunt us. Trenberth said we experience the extra ocean heat when it powers stronger hurricanes, melts ice shelves, raises sea levels and helps fuel El Nino.  

The rest of the heat is dispersed throughout the ocean depths, some sinking to the bottom. 

And that leads us to the final report. For three decades, researchers have been sailing around the world on repeated cruises looking for this stored heat. New research published by NOAA shows that a portion of the heat is being stored in the oceans deepest layers, 6,000 to 20,000 feet down.

The agency concludes, "human-caused climate change has reached one of the most remote corners of the oceans circulatory system."  

It's now clear that the influence of man pervades every nook and cranny of this planet, even the most isolated. And while it's not clear how drastically Earth's system will react, tracking ocean heat is scientists' best tool to measure human fingerprints on the climate system.