Arguments
Earth has a fever, but the heat is sloshing into the oceans
Posted on 3 April 2014 by John Abraham
Much has been made about the Earth's energy imbalance (extra energy absorbed by the Earth). It is clear the Earth is out of balance, in laypersons' terms, it has a "fever". What isn't clear is how bad the fever is. A new study by Dr. Matt Palmer and Dr. Doug McNeall moves us closer to answering this "fever" question.
Matt Palmer and Doug McNeall
These scientists used data from the latest group of climate computer models (CMIP5) to look at the relationships between the energy flows at the top of the atmosphere, the surface temperature of the Earth, and changes in ocean energy. They made (in my mind), three important conclusions.
First, there is a lot of variability in the Earth surface temperature. In fact, these natural fluctuations of the Earth surface temperature (0.3 degrees C per decade) can mask much of the underlying global warming. Consequently, you cannot use Earth surface temperatures over 10 years or so as an indicator of the Earth "fever". As we look over longer periods of time, the "masking" of global warming by internal fluctuations gets smaller; however, even for 15 years or so, natural fluctuations and human-caused global warming can be about the same size.
Second, the authors found that an increase in the ocean energy explains almost all (95%) of the variation in the Earth energy balance. This means that more complete measurements of the global oceans would enable us to better measure the "fever." Finally, for time periods longer than a year, the ocean becomes the dominant storage reservoir for heat.
There were some other conclusions that are noteworthy. For instance, we have heard a lot about how things like volcanoes, human particulate emissions, and solar variability can also impact our understanding of the Earth's "fever." The current paper argues that these "external" influences may be smaller than the natural variability of the Earth system itself – the "sloshing" of energy in/out, and within the Earth system. Another phenomenon that has been reported on quite a bit recently, including by me and my colleague in these pages, is the role of energy storage deep in the ocean. The authors confirm that such storage likely plays a contributing factor to the internal variability.
According to one of the authors, Dr. Palmer, who spoke about the importance of ocean and satellite measurements of the Earth's "fever,"
I totally agree with the potential misleading impression obtained from tracking the trend of shorter time periods. I personally prefer to use a simple spread sheet to follow the rolling 30 year average of the GISTEMP Land-Sea monthly average (a new 30 year average for every new month). That 30 year average continues to rise with the values continuing to be more than 0.16 degrees warmer than a decade before.
Also, it is clear that the phase and magnitude of the ENSO has a significant influence on the global average surface temperature, and it can be a long unpredictable amount of time between significant El Nino influences (such as the current 17 years and going since the 1997/98 El Nino). Any time period that does not include the full range of these significant influences would not really provide a reliable representation of things.
A more interesting point is that even with the extremely high variability of monthly global average surface temperatures (as much as a 0.54 degree C difference from one month to the next in the GISTEMP data set), each month in GISTEMP since 1993 has been warmer than the month 30 years before it, except for January 2011 which was 0.05 degrees cooler than January 1981.
Is "sloshing in and out of" the oceans a newly found phenomenon or didi it already happen in the past? If so, when was the last time energy sloshed in and sloshed out and how was it measured? What deterimines the periodicity of this phenomenon? What are the physical mechanisms causing this energy transfer in and out, in other words: where does this energy come from and how is it transfered in and out?
(Rob P) - multidecadal variations in the strength of the trade winds are responsible for this variation in the rate of ocean heat uptake, see this SkS post: Unprecedented trade wind strength is shifting global warming to the oceans, but for how much longer?.
Since about the year 2000 these trade winds have been much stronger than is typical over the past century. This means that the convergence of surface currents in the subtropical ocean gyres has been enhanced and therefore more heat has been pumped down into the ocean interior than is normal. This will dramatically weaken when the trade winds weaken and, based on some theories of this decadal variability, the intense trade winds have probably shortened the length of the current negative phase of the Interdecadal Pacific Oscillation (IPO).
The oceans will still warm during the positive phase of the IPO, because ocean warming is currently driven by the increased Greenhouse Effect, but the heat uptake should be reduced. Counterintuitively, surface warming will increase much faster - because less heat is being removed from the surface ocean down to deeper layers.
@RobP - "more heat has been pumped down into the ocean". What is the mechanism that pumps heat down without mixing it with the layers on the way down? What is the driver or this pump?
(Rob P) - The driver of the 'pump' are the trade winds which result in the net transport of surface water (ocean currents) at right angles to the wind - to the right of motion in the North Hemisphere, and to the left in the Southern Hemisphere. By blowing toward the west, the trade winds 'push' surface water toward the poles. This divergence of surface water at the equator is why we have upwelling in the central and eastern equatorial Pacific Ocean.
The poleward surface currents out of the tropics collide (in the subtropical ocean gyres) with equatorward surface currents forced by westerly winds at mid-latitudes and, with nowhere else they can go, the currents are forced down into the ocean. Spin-up the wind-driven circulation and you get stronger upwelling at the equator and stronger downwelling in the subtropical gyres. Weaken the circulation and both upwelling and downwelling weaken too. With weak horizontal transport of surface water out of the tropics, the tropical ocean heats up anomalously.
This phenomenon largely exists because we live on a rapidly rotating planet. Vagn Walfrid Ekman realized the seemingly bizarre effects of rotation on the Earth's oceans back in 1905.
We do have some posts coming up on this topic, but I've been dragging my feet because the graphics and animations have to be created.
topal, NASA has a short explanation with pictures.
Topal... Here's an illustration that's even more simple and easy to understand.
What you can see is that, it's not a matter of the heat going straight down through the ocean layers. It's about warmer waters being shifted.
In diagram (a) the upper layer is warmer than the lower layer. In diagram (b) the same amount of heat shows a cooling upper layer and warming lower layer.
[source]
Rob, I know how this works. But the warm water that accumulates to greater depths in the west results in colder water being exposed at the surface in the east. Overall, there is no change in the heat content, it's just redistribution and mixing of existing heat.
(snip)
(Rob P) - No, you don't know how this works. Your line of questioning bears this out.
You appear uninterested in learning, which is my bad because I thought you were interested in learning a little bit about oceanography. Just don't plaster this site with your unsubstantiated opinions as you will find them moderated out - as above.
This is a site reliant on the scientific literature. There are plenty of other sites on the internet that would welcome your unsubstantiated inexpert opinions.
Topal,
Here is anopther version of the same thing others have been trying to help you better understand what is going on.
When La Nina conditions exist a large area of the eastern equatorial Pacific Ocean has cold surface waters upwelling as shown to you by ohers, and able to be learned about from a variety of sources if you really want to better understand what is going on. That colder surface is a circulation of the deeper colder waters and it takes heat out of the air above it (wind and wave action), leading to a global average surface rtemperature lower than a norm or avergae ENSO neutral temparature (because the winds result in the cooling affecting more area than just the cooler surface water region.
When El Nino conditions form the entire area of the equatorial Pacific is warmer leading to much warmer air being circulated around the planet and a higher than "norm or average" global average surface average temperature like the one created by the very strong El Nino of 1997/98 (a similarly strong El NIno has not formed since then, but one will)
I hope that helps.
Topal,
A further clarification. El Nino conditions mean that the average surface temperature of the equatorial Pacific is warmer, La NIna means the overall average is cooler. The following link to the NOAA data of the ONI may help you better understand this. You can see that the variation of the average is significant (several degrees C)
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml
A clarification of my comment @2.
Evaluation of global average surface temperature for time periods that are not long enough to average in the broad range of the significant influences like ENSO (phase and strength) and volcanic dust (amount, nature of the particles, and height and distribution in the atmosphere), can be performed by reasonably accounting for those influences.
The challenge is getting people who want to believe otherwise to stop choosing to focus on information in a way that suits their interest. Some people may never overcome their struggle to better understand what is going on because they won't give up their strong personal desire to get the most possible personal benefit any way they can get away with.
For the sake of the future of humanity (and all other life on this amazing planet), these people need to be disappointed by policy and actions regardless of the impression of popularity and profitability that can be created for the unacceptable unsustainable actions and attitudes they refuse to change their mind about. (That is delving into the politics, but I mention it because I consider it to be the best understanding of what is going on, which is an assessment of the available observations, which is what science is all about).
Topal @6... Previously you asked the question, "What is the mechanism that pumps heat down without mixing it with the layers on the way down? What is the driver or this pump?"
The diagram I showed you @7 explains how it's not a matter of "mixing with the layers on the way down." It's a matter of shifting the thermocline, and the "driver" or "pump" the mechanism is surface winds.
If you understood this in the first place, I'm not clear on why you asked such a question.
Topal... "Overall, there is no change in the heat content, it's just redistribution and mixing of existing heat."
Your question was not in regards to changes in heat content. You asked about mixing and how heat gets distributed to lower layers.
If you're actually interested in ocean-atmosphere coupling here's a really great page that explains all the mechanisms in plain language.
http://eesc.columbia.edu/courses/ees/climate/lectures/o_atm.html
@One Planet Only Forever #2:
"I personally prefer to use a simple spread sheet to follow the rolling 30 year average of the GISTEMP Land-Sea monthly average (a new 30 year average for every new month)"
Aren't we more interested in changes in the warming rate? Why not do your analysis on a rolling linear trend of the last 30 years, instead of a rolling average?
Rolling averages? Not perhaps the best way of smoothing things, particualrly if you are interested in what is happenng at the ends of the time series.
Tamino has a good three-part series on the subject, from earlier this year:
Smooth 1
Smooth 2
Smooth 3
With regard to moving energy or heat from the surface into the deep oceans without warming the middle depths:
Energy transfer by convection or mass transfer has some rather subtle features that may come as a bit of a surprise if someone is stuck in a mind-set of conduction/diffusion thermal transfer.
Let's take the analogy of three rooms with connecting doors. The three rooms have temperatures of +20C, 0C, and -20C. Each room also has a large box, full of air equilibrated to room temperature.
- I pick up the box in the +20C room, walk through the middle room to the -20C room, while at the same time another person picks up the -20C box and walks through the middle room to the +20C room.
- at the end, the +20C room is now colder. It has a box of -20C air, which will (over time) equlibrate with the room, slightly cooling the rest of the room.
- the same happens at the -20C room: it has a box of +20C air which will warm the -20C air slightly as it equilibrates.
Note that there has been no net transfer of mass - each room at the end has lost a box and gained a box of air.
There has been a transfer of energy from the +20C room to the -20C room.
And most important of all: the room in the middle has not changed its temperature (energy content).
The same can heppen in the ocean: warm water from the surface to the deep ocean, offsetting water mass moving from the cold depths to the surface, No net mass transfer, but an energy transfer, and the middle layers just watch in fascination.
Klapper @14,
As I mentioned, what I mean by a rolling average is that I calculate a new 30 year average for every new month of data. And the 30 year rolling average can also show 'rates of change'. More importantly, temporary eroneous fluctuations cannot give credence to unjustifiable misleading claims based on evalautions of temepratures since moments like the last major temporary induced extreme in the global average surface temperature data.
Bob Laidlaw @ 15,
There are indeed many statistical methods to try to figure out what has been happening in the later part of a set of data points in an extensive series of data with values widely, and occasionally rapidly, fluctuating due to significant random influnces.
However, such evaluations can be challenged, and require reworking, as soon as the next randomly influenced value is added. That does not occur with a simplistic evaluation like a 30 year roilling average. Even wildly aberrant values such as the 0.5 C degrees changes of one month to the next or the 0.35 C chnages form one year to the next in the GISTEMP data set are smoothed by beig averaged with the opposite aberations within the larger set of averaged values.
Also, as I clarified, accounting for the random significant influencing factors would allow a more reasonable evaluation.