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In this De-Natured segment of Nature League, Brit breaks down a recent scientific journal article about a new estimation of heat in the oceans.

Article citation:

L. Resplandy, R. F. Keeling, Y. Eddebbar, M. K. Brooks, R. Wang, L. Bopp, M. C. Long, J. P. Dunne, W. Koeve & A. Oschlies

Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition

Nature, 2018

Article link:

https://www.nature.com/articles/s41586-018-0651-8

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Welcome back to Nature League!

This month’s De-Natured has a bit of a twist, so we figured we’d let you in on some breaking news before getting started. The paper we’re presenting in this episode had a correction published just this week, but our De-Natured video was recorded last week.

The introduction and methods section that we’ll go through are still accurate. The correction has to do with the results. At the end, we’ll dish all the drama about how the error was discovered and what it means for the results and science in general.

Enjoy! [CHEERY INTRO MUSIC]. On Nature League, we spend the third week of each month exploring a current trending article from the peer-reviewed literature. Scientific information isn’t just for scientists.

It’s for everyone! It just requires a bit of a break down. For this month’s De-Natured segment, we’re going to look at an article released in November 2018 in the journal Nature.

In this month’s Lesson Plan and Field Trip, we touched on the relationship between the ocean and the Earth’s climate. One part of this relationship is that the ocean is one of the biggest storage centers of carbon on Earth. And aside from trapping carbon, the ocean also traps heat, or thermal energy.

In fact, the ocean takes up close to 90% of the excess energy produced as Earth warms over time. But /measuring/ the heat content of the ocean is tricky to say the least. In the past, total heat content was estimated by combining and analyzing tons of ocean temperature spot measurements.

A sensor network dubbed Argo has been taking these measurements during recent decades, and expanded coverage in 2007. Even though the Argo network is extensive, the ocean is massive, and there are lots of gaps in coverage. In addition to gaps, temperature-based estimates like these can only sample the top half of the ocean.

These issues result in estimated warming trends with uncertainties up to 25-50%. But what’s a little uncertainty in scientific measurements? Being off about ocean temperatures isn’t that bad...right?

Uncertainty is part of any field of study, but when it comes to climate science and modeling, there are massive consequences on the line. Just think - international treaties and plans like the Paris Agreement are based on measurements that include ocean temperatures. And we haven’t had the most accurate game plan in place...

That is, until now. In this paper entitled, “Quantification of ocean heat uptake from changes in atmospheric oxygen and carbon dioxide composition”, scientists have proposed a revolutionary new way to measure the heat content of the ocean, and their results point to some brand new and far-reaching conclusions about Earth’s climate. In this particular study, the researchers present a brand new method based on the abundances of gases in the atmosphere and how they change over time.

It goes something like this:. Gases are affected by temperature, and how much a gas dissolves in sea water depends on this factor. When the ocean warms, oxygen and carbon dioxide gas doesn’t dissolve as much in the water, so the ocean loses gas.

This loss of gas can be measured by comparing against the gains of gas in the atmosphere. Instead of relying on temperature measurements, the team measured the concentration of atmospheric oxygen and carbon dioxide in a new metric called “atmospheric potential oxygen, or APO”. What’s great is that we have highly precise atmospheric oxygen measurements going back to 1991, and back to 1958 for carbon dioxide, meaning this new method has almost three decades worth of quality data to use.

Gases move around a lot, though, and it’s hard to pin down whether the change in atmospheric oxygen and carbon dioxide was in response to processes in the ocean versus somewhere else. However, the team used ocean-specific ratios of gases to make the APO insensitive to gas exchanges on the land. So let’s dig into their APO measurement for a bit.

So overall, the team came up with a new and more precise way to measure ocean warming. But they didn’t stop there - they actually used this new method to obtain an estimate. Here’s what they found:.

The world’s oceans absorbed more than 13 zetajoules of heat energy each year between 1991 and 2016. A joule is a unit of energy, and that prefix zeta means there are /21 zeroes/. In other words, that means the oceans are taking in about 150 times more energy each year than what humans produce each year as electricity.

So now for some perspective. This estimate is 60% higher than the previous temperature-based estimate that’s been used up until now. Countries are currently working toward keeping the rise in global temperatures under 2 degrees Celsius.

Staying under a 2 degree rise requires some budgeting, particularly of carbon emissions. However, with this new data, the carbon dioxide emission budget we’ve calculated needs to be reduced another /25%/ to reach that goal. At the time of releasing this episode, this paper has only been out for a couple of weeks.

However, it has taken the climate science community and general public by storm. Here’s why I think this article is making the rounds. Upgrades in previously faulty methodologies always make a big splash, especially when so much hinges on them.

Imagine taking temperatures with a thermometer that had the wrong number spacing on it. The whole time you’d used it you weren’t picking up any kind of fever at all. So when you finally got a thermometer that worked you’d be like, “whoaaa, there it is!” That’s sort of what happened here.

Ocean warming trends have been based on less than ideal methodologies, and that means our climate change estimates and legislature about carbon emissions have been based on faulty measurements. Because of that, this update on ocean temperature could have massive global consequences. Keep in mind that ocean warming measurements have been used in the standard assessment report for global climate change by the leading authority on the subject- the Intergovernmental.

Panel on Climate Change, or IPCC. In their fifth and most recent assessment report, the IPCC used ocean warming estimates that were way lower than what was found here. This means that when the IPCC and participating countries set their carbon emission legislations, they were being overly optimistic about just how much heat the oceans are absorbing.

The night before we were scheduled to upload this De-Natured episode, I got a news alert about an error found in this particular article. Here’s what happened:. The article was published in Nature, one of if not the most prestigious scientific journals on Earth.

On November 6th, less than a week later, an independent climate scientist named Nic Lewis posted an informal review of the paper on a blog. In his post, he recalculates the trends reported in the Nature article and shows that there were errors in the estimation of the change in APO due to climate, and major miscalculations in the uncertainty reported for the results. Here’s what happened next.

The authors got ahold of this blog post, and immediately considered Lewis’s critiques and corrections. On November 9th, co-author Ralph Keeling released a statement saying that the authors were looking into the errors brought up by Lewis, and that they take full responsibility for the mistakes. By November 14th, the story of these errors spread throughout global media outlets, including the news article that alerted me.

So where does all of this leave us? Overall, a few things still stand true. For instance, the new methodology for measuring warming is still valid, as well as the insights they found regarding the connections between the ocean and atmosphere.

Also, the authors note in their news release that their calculations of overall heat uptake by the oceans are still mostly accurate- the issue is with the margin of error. The redone calculations show that the uncertainty is much larger than they thought, meaning this new method at present has similar uncertainty to previous methods. So yes, the ocean is taking in massive amounts of heat energy.

And yes, the ocean is warming. And yes, the emissions guidelines set by the IPCC might need to be adjusted in the future. But does this mean that scientists have been lying to us about climate trends as some outlets are interpreting it?

Absolutely not! It just means that right now, we are seeing the process of science in action. Even though errors weren’t found throughout the official peer review process, peer review continued to happen even after publication - in the form of a blog post no less!

Science isn’t a bunch of facts - science is a process. And that process just so happens to include a series of trial, error, calculations, mistakes, recalculations, and review. The moral of this story?

We should keep an open and skeptical mind about new scientific results while respecting and welcoming outside perspectives. Thanks for watching this episode of De-Natured here on Nature League. If you know someone interested in the ocean or climate change or heard someone mention this study, share this video with them so they can learn more.

And to keep going on life on Earth adventures with us, make sure to go to youtube.com/natureleague and subscribe.