There is a story that I hope is not apocryphal, told among anthropologists. It goes like this. A graduate student in Cultural Anthropology went to the field, to a site in the American Southwest, where he intended to document the lifeways of a group of Native Americans living there. On arrival at the field site, he was directed by helpful locals to the home of a very old man who, they said, knew all about the group’s history and culture. This would be a great place to start his research.
So, he went there, found the old man, who invited him to sit under the shade of a large cottonwood tree out in front of his old, one room home.
Sure enough, the young anthropologist-in-training found the answer to question after question that he had about the local kinship system, ways of finding and growing food, and so on. But every now and then, the old man would hesitate over a certain question, then, excuse himself, entering his humble abode, whence he would return a few minutes later to resume their conversation. After emerging form the house, the old man would have an answer, sometimes quite detailed, but also, somewhat stilted, for the young scholar’s question.
It did not take too long for the young student to realize that there must be another old man, an even older, wiser, man inside that house, to which his informant deferred on certain matters. Eventually, the young student got up the nerve to ask the old man if he could come inside the house, to see how he lived, and without hesitation the old man invited him in.
Sure enough, inside the house, there was an older source of information about the lifeways of American Indians living in this region.
The old man had a book, fifty years old or so, but still quite useful, for when the young whipper-snapper anthropology students came around. He had most of it memorized, but every now and then…
The moral of the story is that sometimes the truth lies just below the surface. And, when it comes to human caused global warming, the truth, the key to understanding the whole process, lies beneath the surface of the sea.
Some very important research came out a few weeks ago, and the same team has published a related, new, finding just today, and you need to know all about all of it. In order to fully understand its significance, I’d like first to guide you through a simple argument.
Look at the following graph.
That is the long term “Keeling Curve” representing the amount of CO2 in the Earth’s atmosphere, and how it has changed over time as humans have burned fossil fuels, releasing the stored Carbon from solid form. There are several things to see here, but I want you to focus on two of them: 1) It is going up and has been doing so at a high rate since the middle of the 20th century (though it started to go up before 1800); and 2) it is very smooth, despite a pronounced seasonal jaggedness.
CO2 is a greenhouse gas, and the effect it has on the atmosphere is to recruit other greenhouse gasses, and all together these greenhouse gasses cause the surface temperature of the planet to go up over time. What is the “surface temperature?” Two things.
First, it is the temperature of the air at head height, taken at numerous weather stations around the world. Like this:
Second, it is the temperature of the surface of the sea, measured across all the world’s oceans using satellites, to produce information that looks like this:
The two of those sources of information produce a global average, usually in the form of an anomaly value, which compares the current temperature with some baseline. It is beyond the scope of this writing to fully explain why the anomaly measurement is used instead of a simple temperature, but if you think about it for a second you’ll realize it is obvious. Change is easier to measure accurately than an absolute value, if you have a wide range of data sources and are combining two or more very different kinds of measurements, and the anomaly represents change. Anyway, there are several different groups of scientists who maintain a set of data using the above described head-height and satellite data, and older data (pre-space ship) that approximates this, to produce a long term measurement of average surface temperature. Here is one view of this, using NASA’s Goddard Institute of Space Science data:
Please glance back at the Keeling Curve graphic of CO2 over time, then think for a moment about CO2 and global warming, and then, look at the graph of surface temperature over time, and explain to me why the CO2 can go up so smoothly but the temperature rise caused by CO2 induced warming is all ziggilly-jageddly.
We could now spill a gigabit of digital ink addressing that question, and indeed it is an important and fascinating one. Consider that the actual variation over time in a key variable like surface temperature is the actual weather, in a sense. When that graph zigs up, that’s a warm year for many, or perhaps a year with little snow, or a year where the warm air and sea surface soaked the atmosphere so there were floods. When the graph jags down, that may be a year of relative dryness somewhere, or very cold winters, or whatever. So that phenomenon, the cause of warming, runs apace over time but the effect of warming wildly varies. This is vitally important.
But it is also true, verified by the research of a few week ago, that this effect, long term, big scale, in the ponderous manner of geology rather than the fickled nature of weather, is actually just as smooth and direct and clean and causally clear as it could possibly be. If you use a different graph, based on different data.
Imagine throwing one of these into the ocean.
That there is an Argo float. You can learn all about them by reading this overview by one of the scientists who produced the recent research of which we speak, John Abraham. Instead of measuring temperature of the surface of the sea, the Argo float argonauts is way into the deeper sea, to measure temperature there. This is the latest of a series of project measuring deeper ocean temperature. Today, scientists have enough information to reconstruct the temperature of the whole ocean (or the top whole bunch of it) over long term.
When we look at an estimate of the Earth’s ocean temperature, at depth, we get the line shown here in red, the lower one on the graph:
Here you can directly compare the surface temperature as described above ( the green squiggle) and the ocean temperature. The increase in variation as you go back in time in the ocean is due to the weakening of the data set itself. The zone of the graph that is in pink gives the best data (thought that is not what the pink means) and clearly indicates that ocean temperature does not ziggidy-jag up and down like the surface temperature does.
The main takeaway from this information is the second thing you notice when you look at this graph. The first takeaway, of course, is that deeper ocean temperature does not vary wildly like surface temperature does, but the second takaway is that CO2’s steady rise and the ocean’s actual temperature (not just the surface) steady rise are both smooth, upward, and that today, at this moment, both are higher than at any time in the geologically recent past. Global warming does not occur in fits and starts. It continues apace, is directly correlated to CO2 in the atmosphere, and we have more of it now than we had before.
Also of critical importance: This is a lot of heat, a lot of energy. The total amount of heat stored in the ocean is several orders of magnitude greater than just on the surface. You’ve heard the expressoin, “The tail wagging the dog,” which refers to something that should not be a controlling factor taking over as a controlling factor. That is what we have here. The tail is the surface temperature, which drives the public (and to a large extent, scientific) narrative of global warming. The dog is the ocean. The dog-ocean is sitting there becoming steadily warmer, apace with changes in atmospheric chemistry, while the surface of the top of the ocean, and the very bottom (head-height) of the atmosphere zig and zag around a long term average, gaining all of our attention but often misleading us when it comes to the two basic questions: is global warming for real caused by our release of fossil Carbon? (yes) and is global warming slowing down now and then, giving us hope that there is some other unknown factor that could come along and save the day? (no).
That is the main finding of the most recent research paper, of a few weeks ago (details provided below), but there is a second more esoteric set of conclusions that I will summarize. The nature, timing, and magnitude of the exchange of heat between the global ocean and the atmosphere, which manifests as things like El Nino and La Nina, monsoonal seasonal variation, a so-called “hiatus” in warming that was falsely used to describe some of the squiggly surface temperature data, and so on, are of great importance in tracking warming and understanding its effect. The recent study looked at some of the measures developed over time to describe these fluctuations, to see if they correlated with flux in deeper ocean temperature more recently measured. The research did not find a good relationship, for recent changes in surface temperatures known as the “pause” or “hiatus,” further supporting the idea that the hiatus is an irrelevancy, a random fluctuation in the data that got a lot of science deniers off, but that we should largely ignore.
About today’s finding. This is a “News and Views” item in Advances in Atmospheric Sciences reporting that, when we look at the ocean heat, 2018 is the warmest year on record. The report provides this graph, which can replace all your old graphs of global warming if you like:
… and this table:
The meaning of it all:
- Global warming is real;
- Global warming is caused by CO2 and other human-released greenhouse gasses;
- Global warming is happening every year, with the temperature going up every year, and this has been happening at an alarming rate for decades;
- What we see on the surface is important and is often the part that matters to us on a day to bay basis; but
- The cause of what we see on the surface is not always so obvious; but
- Deeper realities are discoverable if you are willing to look for them.
Decadal Ocean Heat Redistribution Since the Late 1990s and Its Association with Key Climate Modes by Lijing Cheng , Gongjie Wang, John P. Abraham, and Gang Huang. Climate 2018, 6, 91; doi:10.3390/cli6040091.
Abstract: Ocean heat content (OHC) is the major component of the earth’s energy imbalance. Its decadal scale variability has been heavily debated in the research interest of the so-called “surface warming slowdown” (SWS) that occurred during the 1998–2013 period. Here, we first clarify that OHC has accelerated since the late 1990s. This finding refutes the concept of a slowdown of the human-induced global warming. This study also addresses the question of how heat is redistributed within the global ocean and provides some explanation of the underlying physical phenomena. Previous efforts to answer this question end with contradictory conclusions; we show that the systematic errors in some OHC datasets are partly responsible for these contradictions. Using an improved OHC product, the three-dimensional OHC changes during the SWS period are depicted, related to a reference period of 1982–1997. Several “hot spots” and “cold spots” are identified, showing a significant decadal-scale redistribution of ocean heat, which is distinct from the long-term ocean-warming pattern. To provide clues for the potential drivers of the OHC changes during the SWS period, we examine the OHC changes related to the key climate modes by regressing the Pacific Decadal Oscillation (PDO), El Niño-Southern Oscillation (ENSO), and Atlantic Multi-decadal Oscillation (AMO) indices onto the de-trended gridded OHC anomalies. We find that no single mode can fully explain the OHC change patterns during the SWS period, suggesting that there is not a single “pacemaker” for the recent SWS. Our observation-based analyses provide a basis for further understanding the mechanisms of the decadal ocean heat uptake and evaluating the climate models.
2018 Continues Record Global Ocean Warming, by Lijing CHENG, Jiang ZHU, John ABRAHAM, Kevin E. TRENBERTH, John T. FASULLO,
Bin ZHANG, Fujiang YU, Liying WAN, Xingrong CHEN, and Xiangzhou SONG. Advances in Atmospheric Sciences, 36. Available here.
Other write-ups on this work:
2018 was hottest year on record for oceans by Aris Folley