Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition.
The ocean is the main source of thermal inertia in the climate system1. During recent decades, ocean heat uptake has been quantified by using hydrographic temperature measurements and data from the Argo float program, which expanded its coverage after 20072,3. However, these estimates all use the same imperfect ocean dataset and share additional uncertainties resulting from sparse coverage, especially before 20074,5. Here we provide an independent estimate by using measurements of atmospheric oxygen (O2) and carbon dioxide (CO2)—levels of which increase as the ocean warms and releases gases—as a whole-ocean thermometer. We show that the ocean gained 1.33 ± 0.20 × 1022 joules of heat per year between 1991 and 2016, equivalent to a planetary energy imbalance of 0.83 ± 0.11 watts per square metre of Earth’s surface. We also find that the ocean-warming effect that led to the outgassing of O2 and CO2 can be isolated from the direct effects of anthropogenic emissions and CO2 sinks. Our result—which relies on high-precision O2 measurements dating back to 19916—suggests that ocean warming is at the high end of previous estimates, with implications for policy-relevant measurements of the Earth response to climate change, such as climate sensitivity to greenhouse gases7 and the thermal component of sea-level rise8. – L. Resplandy, R. F. Keeling, Y. Eddebbar, M. K. Brooks, R. Wang, L. Bopp, M. C. Long, J. P. Dunne, W. Koeve & A. Oschlies Nature, volume 563, pages105–108 (2018)
This is what real news looks like.
Earth’s oceans appear to have been warming more extensively than we’ve realized. This insight comes on the heels of recent IPCC findings that the harm likely from 20C of global warming will likely be greater than previously thought, and that limiting warming to something more like 1.50C would be substantially safer. That IPCC report also suggested nations have only a brief time window in which to effect such a soft landing.
- First, with regard to uncertainties in what we think we know. At some point in my youth (the 1950’s? 1960’s?) my statistician father shared a result he’d seen in a peer-reviewed paper somewhere that looked at “variations” in physical constants over time. His narrative went something like this (in italics here, but NOT an exact quote):
The authors found that experiments and careful measurements would yield a published value for this or that physical constant, complete with error bars. For the next several years, subsequent publications by different authors or groups would refine the estimate, but always within the earlier error bars. Then someone would come along with an entirely new and (arguably more reliable – that’s how it would get published) approach, yielding a new estimate, one outside the earlier error bars. For the next several years, subsequent estimates would refine that new number, again within the (now new) error bars. They demonstrated this phenomenon across several physical constants, not just one.
As a statistician, he was always on the lookout for misuse, abuse, and misrepresentation of statistics, especially by scientists from other disciplines. Whatever paper he’d seen affirmed an innate skepticism he held.
In my career since, a couple of similar stories have stood out. Early on after I’d made a switch in graduate school from solid-state physics to geophysical sciences (late 1960’s), I read a paper reporting new estimates of the density of the Martian atmosphere, derived from radio occultation of probes orbiting that planet. The results showed an atmosphere perhaps one percent as dense as Earth’s at the surface, an order of magnitude less than what the researchers had expected to find based on prior estimates derived from other techniques/considerations.
Years later, I was working closely with Ned Ostenso, then Acting Chief Scientist of NOAA, who was telling me about his days as a graduate student in geology at the University of Wisconsin. He and several other students were tapped to do a transect of the Antarctic as part of the International Geophysical Year, and take soundings of the thickness of the Antarctic ice sheet. They radioed back to their faculty advisers some estimates the order of ten thousand feet. Their advisors radioed back: You’re an order of magnitude high. Recheck equipment… Of course it turned out that the students had gotten their sums right.
- Second, the news from Resplandy et al. ought to be rocking our world. But it’s not. That’s because we’ve been swimming quite a while in another, stormier sea (itself increasingly devoid of life-sustaining oxygen?) that makes it hard for this heat uptake and its implications to register. That’s of course the virtual ocean of information, including seas and swell of breathless news headlines. competing for eyeballs and therefore focused laser-like on the inflammatory, the polarizing, the urgent, the personality-based aspects of our world – and less on underlying issues. Jobs, the economy, and trade? Healthcare? Education? Immigration? The environment? It’s easy to pay more attention to the messengers than the message.
Reminiscent of the cockpit resource management challenge: stay focused on situational awareness versus cockpit hierarchy and squabbling about irrelevancies. It’s also reminiscent of a booklet by Charles Hummel that became a management classic in the 1960’s entitled The Tyranny of the Urgent. Hummel argued that the merely urgent and the vitally important constantly compete for our attention – and that the urgent almost always wins (think about what happens when you’re working on a project and the phone rings or an e-mail from your boss pops up). A corollary is that the urgent almost always has a deadline, where the vital (e.g., how will humankind cope with global warming) almost never does.
I’d write about this at greater length, but it’s time for me to go vote.