The 2007-2008 Global Cooling Event: Evidence for Clouds as the Cause
September 26th, 2009 by Roy W. Spencer, Ph. D.
As I work on finishing our forcing/feedback paper for re-submission to Journal of Geophysical Research – a process that has been going on for months now – I keep finding new pieces of evidence in the data that keep changing the paper’s focus in small ways.
For instance, yesterday I realized that NASA Langley has recently updated their CERES global radiative budget measurement dataset through 2008 (it had previously ran from March 2000 through August 2007).
I’ve been anxiously awaiting this update because of the major global cooling event we saw during late 2007 and early 2008. A plot of daily running 91-day global averages in UAH lower tropospheric (LT) temperature anomalies is shown below, which reveals the dramatic 2007-08 cool event.
I was especially interested to see if this was caused by a natural increase in low clouds reducing the amount of sunlight absorbed by the climate system. As readers of my blog know, I believe that most climate change – including “global warming” – in the last 100 years or more has been caused by natural changes in low cloud cover, which in turn have been caused by natural, chaotic fluctuations in global circulation patterns in the atmosphere-ocean system. The leading candidate for this, in my opinion, is the Pacific Decadal Oscillation…possibly augmented by more frequent El Nino activity in the last 30 years.
Now that we have 9 years of CERES data from the Terra satellite, we can more closely examine a possible low cloud connection to climate change. The next figure shows the changes in the Earth’s net radiative balance as measured by the Terra CERES system. By “net” I mean the sum of reflected shortwave energy (sunlight), or “SW”, and emitted longwave energy (infrared) or “LW”.
The changes in the radiative balance of the Earth seen above can be thought of conceptually in terms of forcing and feedback, which are combined together in some unknown proportion that varies over time. Making the interpretation even more uncertain is that some proportion of the feedback is due not only to radiative forcing, but also to non-radiative forcing of temperature change.
So the variations we see in the above chart is the combined result of three processes: (1) radiative forcing (both internal and external), which can be expected to cause a temperature change; (2) radiative feedback upon any radiatively forced temperature changes; and (3) radiative feedback upon any NON-radiatively forced temperature changes (e.g., from tropical intraseasonal oscillations in rainfall). It turns out that feedback can only be uniquely measured in response to NON-radiatively forced temperature changes, but that’s a different discussion.
The SW component of the total flux measured by CERES looks like this…note the large spike upward in reflected sunlight coinciding with the late 2007 cooling:
And here’s the LW (infrared) component…note the very low emission late in 2007, a portion of which must be from the colder atmosphere emitting less infrared radiation.
As I discuss at length in the paper I am preparing, the physical interpretation of which of these 3 processes is dominant is helped by drawing a phase space diagram of the Net (LW+SW) radiative flux anomalies versus temperature anomalies (now shown as monthly running 3-month averages), which shows that the 2007-08 cooling event has a classic radiative forcing signature:
The spiral (or loop) pattern is the result of the fact that the temperature response of the ocean lags the forcing. This is in contrast to feedback, a process for which there is no time lag. The dashed line represents the feedback I believe to be operating in the climate system on these interannual (year-to-year) time scales, around 6 W m-2 K-1 as we published in 2007…and as Lindzen and Choi (2009) recently published from the older Earth Radiation Budget Satellite data.
The ability to separate forcing from feedback is crucial in the global warming debate. While this signature of internal radiative forcing of the 2007-08 event is clear, it is not possible to determine the feedback in response to that temperature change – it’s signature is overwhelmed by the radiative forcing.
Since the fluctuations in Net (LW+SW) radiative flux are a combination of forcing and feedback, we can use the tropospheric temperature variations to remove an estimate of the feedback component in order to isolate the forcing. [While experts will questions this step, it is entirely consistent with the procedures of Forster and Gregory (2006 J. Climate) and Forster and Taylor (2006 J. of Climate), who subtracted known radiative forcings from the total flux to isolate the feedback].
The method is simple: The forcing equals the Net flux minus the feedback parameter (6 W m-2 K-1) times the LT temperature variations shown in the first figure above. The result looks like this:
What we see are 3 major peaks in radiant energy loss forcing the system: in 2000, 2004, and late 2007. If you look at the features in the separate SW and LW plots above, it is obvious the main signature is in the SW…probably due to natural increases in cloud cover, mostly low clouds, causing internal radiative forcing of the system
If we instead assume a much smaller feedback parameter, say in the mid-range of what the IPCC models exhibit, 1.5 W m-2 K-1, then the estimate of the radiative forcing looks like this:
Note the trend lines in either case show a net increase of at least 1 W m-2 in the radiant energy entering the climate system. The anthropogenic greenhouse gas component of this would be (I believe) about 0.4 W m-2, or a little less that half. I’ll update this if someone gives me a better estimate.
So, what might all of this mean in the climate debate? First, nature can cause some pretty substantial forcings…what if these occur on the time scales associated with global warming (decades to centuries)?
But what is really curious is that the 9-year change in radiative forcing (warming influence) of the system seen in the last two figures is at least TWICE that expected from the carbon dioxide component alone, and yet essentially no warming has occurred over that period (see first illustration above). How could this be, if the climate system is as sensitive as the IPCC claims it to be?
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“beng:
Colder surface ocean water acts as a heat-sink, its effect depending on the amount & depth of mixing.”
Reply:
Actually I’m doubtful about that. Colder water cools the air but the amount of energy taken from the air is far too small to have a significant effect on the much denser water and that extra energy just goes to more evaporation anyway.
If there is rougher water one doesn’t get more downward mixing because rough water has a larger surface area and, again, that increases evaporation. It’s usually windier as well – more evaporation.
I’ve yet to find a plausible means of getting significant energy from warm air into cooler water and the ‘ocean skin’ theory of the AGW proponents doesn’t cut it either because of the evaporative response.
Furthermore if the ocean energy content could increase from energy transfer from air to water the oceans would have boiled away long ago rather than surviving huge volcanic disruptions and meteorite strikes over the billions of years since liquid oceans formed.
Instead of oceans keeping coastal regions cool the coastal regions would heat up the nearby oceans. That doesn’t happen though the shallower water around coasts is a little warmer than the ocean bulk because of solar penetration.
Stephen Wilde (12:09:37) :
Furthermore if the ocean energy content could increase from energy transfer from air to water the oceans would have boiled away long ago
No, they wouldn’t, because the heat transfer depends on the temperature difference, which would decrease [and go sway] as the oceans heat up.
Mr Spencer
In brief
As I understand it, there is a lag of 6 years between oceanic warming from the sun, and “global cooling” from cloud cover and precipitation,as lower lying clouds give a cooling effect. This was predicted by some oceanographers (I forget which off hand) in 2001-2002, that around 2007, cooling would occur. Climatologists of course said at the time that we’d be on a path of yearly warmer global temperatures.
Re Dr Spencer
While I fully understand your phase-space diagrams, I wonder if they might not be more visually instructive if they were presented as 3D plots with lag time as the 3rd dimension, thus avoiding the need to follow the “strings”.
The 2007-2008 “global cooling” event? Don’t these years still belong to the warmest 10 since records began? (http://www.cru.uea.ac.uk/cru/info/warming/)
Regardless, when discussing climate, how can one refer to 2 years as a “global cooling event”?
“Leif Svalgaard:
Stephen Wilde (12:09:37) :
Furthermore if the ocean energy content could increase from energy transfer from air to water the oceans would have boiled away long ago
No, they wouldn’t, because the heat transfer depends on the temperature difference, which would decrease [and go sway] as the oceans heat up.”
Reply:
Thank you Leif. I had doubts about that as soon as I confirmed the post. The lack of an edit function is a problem.
Mind you according to AGW theory warmer air leads to warmer oceans which leads to more water vapour which leads to warmer air and an ever increasing spiral to catastrophe so the temperature difference doesn’t go away, it leads to a feedback loop of warming.
I think we can agree that the world doesn’t seem to work that way.
The difference between (1) the work of Dr Spencer and others posted here and (2) the Alarmists is that the first is science as it is supposed to function, in all its fragmentary and messy reality, and the second is a foregone conclusion trumpeted as ‘science’ for political ends. That makes the public debate one-sided, because we cannot tie up the Realist view into one neat package.
To the question, “If not CO2, how do you explain the warming?” we may answer: (A) looks like there was very little if any warming at all, because the data stinks; and (B) it was probably caused by natural cycles, which are enormously complex and poorly-understood. That is markedly unsatisfying to the average TV watcher.
John F. Hultquist is right: we need “a coherent story,” a Unified Theory, that the average science reporter can understand and present in 300 words, one that directly contravenes (‘disproves’) the AGW litany. Maybe with these current observations about the sun’s gravitation driving lunar-tidal cycles driving ocean cycles driving climate cycles (with some cosmic rays thrown in) we are getting close. Can we have something ready for Copenhagen, please?
/Mr Lynn
tallbloke (03:30:26)
Heat isn’t an easy thing to understand. In a liquid, it will asymptotically approach a state where all energy is evenly distributed. In other words, in nature there is a tendency to the dissipation (energy loss). If you heat to 70C a pan of water in a totally isolated environmment, considerably larger than the pan and stove ( a totally sealed kitchen) the heat, after the heat source has been switcced off, will disippate, as energy can change form one form to another. Even in a vacuum flask where convection and conduction is prevented its energy will degrade. Three days later, why isn’t it still at 70C? Degradation of energy is the essence of entropy
Also, when evaporation from oceans takes place from solar from heating, huge amounts of water vapour and heat are released into the air and into space
Remember to take into account the effects of jet contrails. These may be leading to increases in cloud cover. They would vary with economic conditions and the price of oil.
Bart Verheggen (13:06:02): My my, that’s a rather silly, and hysterical reaction. I never imagined that anyone was still denying that the temperature of the Earth decreased during that time. That was a major “event” and your criticism that it isn’t climate is irrelevant, since we are in fact 1. discussing it in a context which makes it relevant to other discussions about climate (that is, how clouds and water vapor respond to warming and cooling).
@DGallagher (10:57:41) :
In no way was I attempting to “preach to the pope.” I am well aware of Dr. Spencer’s credentials and experience. I questioned why the assumption that the SW component was mostly due to low clouds. Could other factors such as aerosols be a significant factor? My question was based on the post content and perhaps with more details I would be convinced.
Secondly, my link was certainly not for Dr. Spencer but for the rest of us who may not realize how difficult it is to measure trends in cloud cover or other cloud-related data.
P Wilson (13:31:43) :
tallbloke (03:30:26)
Heat isn’t an easy thing to understand. In a liquid, it will asymptotically approach a state where all energy is evenly distributed. In other words, in nature there is a tendency to the dissipation (energy loss). If you heat to 70C a pan of water in a totally isolated environmment, considerably larger than the pan and stove ( a totally sealed kitchen) the heat, after the heat source has been switcced off, will disippate, as energy can change form one form to another. Even in a vacuum flask where convection and conduction is prevented its energy will degrade. Three days later, why isn’t it still at 70C? Degradation of energy is the essence of entropy
The only way to interpret entropy is as the means by which we measure the amount of energy dispersed or diffused out to more available microstates in a process.
The degradation of the energy consists on the transformation from one form of energy into another form that would not be available for doing work in our limited cosmos.
Firstly, Scott Mandia. Without aerosols, clouds would not exist. Secondly, naturally occurring aerosols are the majority. So it poses the question – if clean air acts led to global warming, then suddenly we must be secretly producing more aerosols, or else this aerosol equation is much more complicated than was originally thought. Or could it be PDO conditions instead?
According the Anthrpogenic determination, the period from 1940-1976 was of declining temps due to anthropogenic aerosols – yet this so called aerosol forcing lasted well into the 80’s. Since aerosols have a local effect, this should only have been in the North hemisphere – yet this period from the 40’s the the late 70’s was global. So: was it aerosols or the pacific climate change of the 1970’s? The evidence for the climate change is squarely on the pacific climate change of 1977
commieBob (19:56:03) :
I work with servo systems too.
I see a servo with ringing on several time scales, (~1000 & ~70Yrs being just two).
DaveE.
P Wilson (13:31:43) :
Because convection & especially conduction is limited not prevented.
DaveE.
Nasif Nahle (17:00:40) :
In physics, very little is understood of heat and energy transformations. In the case of black body radiation at normal temperatures, if it is giving off radiation, then it is losing heat, and when it loses enough it receives heat from the ambient temerature. (so much for the Stefan Boltzman constant). This principle operates with the climate. so called Re-radiation from earth stabilises at the ambient temperature, and since heat is a poor conductor, even the effect of ambient air is greater than that of re-radiation: In other words – re-radiation is virtually non-existent.
This is the problem with much climatology. It thinks there is a huge equation of mechanical energy budgets, that somehow, incoming radiation is a constant that has to leave in the same magnitude.
I think the flask experiment – even one in a 100% heat sealed chamber is quite a good demonstration of how heat efectively disappears according to the 2nd law of thermodynamics, and that cooling is autonomous than dependent.
I’m confused
LW + SW shows continual energy gain (average) fro 2000 to 2008 with a big gain at end of 2007. I.e. there should be a continual temp increase with big shift upwads in 2007.
The sw and lw separated plots also show a massive gain at end of 2007
BUT UAH lt shows a temp drop at this point. The peak reflection of SW gives instant cooling but the minimum loss shows no instant heating.
Looking at AMSU-A data and CERES data shows little correspondance:
short wave http://img30.imageshack.us/img30/9646/amsuaceres85nssw.jpg
SW/LW http://img16.imageshack.us/img16/7175/amsuaceres85nsswlw.jpg
Lokking at hadcrut3v also shows little correspondance:
http://img12.imageshack.us/img12/3622/hadcrut3vceres85nsswlw.jpg
Any explanation greatfully received.
Thanks for the reply Dave E, but after studying the thermodynamics of William Thomson, (1st Baron Kelvin) – some time ago, and modern variations thereof and no doubt to my discredit, I see heat in a different way to modern physics, which – I hope I am wrong – contains errors of principle due to the determination of engineering and technology as the driving force of physics.
Richard Mackey – would appreciate a copy of your paper.
Don’t really like to publish my email address – tends to attract too many flies.
Could I give you a fax number in Canada and thus send you my email address by return fax?
I’m sorry, but is there not one scientist who can answer these questions for me?
How many PPM of H2O are there in the atmosphere at any given time? What is the history?
I would also like to know; At what levels of the atmosphere does CO2 and H2O occupy according to their position in the atmosphere?
bill (18:06:45) :
“I’m confused
LW + SW shows continual energy gain (average) fro 2000 to 2008 with a big gain at end of 2007. I.e. there should be a continual temp increase with big shift upwads in 2007.”
This confused me also. Dr Spencer does not use the standard convention that heat gained by the system is a positive quantity. With the standard convention LW and SW would be negative quantities, indicating heat leaving the system. But here they are positive, so that the increase at the end of 2007 for example indicates cooling not heating. With the standard convention the trend lines in the last two figures would have the “right” slope to indicate warming (upward instead of downward).
P Wilson (18:02:29) :
Nasif Nahle (17:00:40) :
In physics, very little is understood of heat and energy transformations. In the case of black body radiation at normal temperatures, if it is giving off radiation, then it is losing heat, and when it loses enough it receives heat from the ambient temerature. (so much for the Stefan Boltzman constant). This principle operates with the climate. so called Re-radiation from earth stabilises at the ambient temperature, and since heat is a poor conductor, even the effect of ambient air is greater than that of re-radiation: In other words – re-radiation is virtually non-existent.
Perhaps you meant “air is a poor conductor of heat”? I agree on your last assertion, especially when considering induced negative emission, which cancels absolutely the idea of re-radiation.
This is the problem with much climatology. It thinks there is a huge equation of mechanical energy budgets, that somehow, incoming radiation is a constant that has to leave in the same magnitude.
A big problem because all the systems tend to thermalization. Fortunately for us, living beings, thermal equilibrium does not happen by the thermal contact Sun-Earth, neither through the thermal contact Earth-Space. If we reached the equilibrium at any of those systems, we would be toasted in the first case and congealed in the second case.
I think the flask experiment – even one in a 100% heat sealed chamber is quite a good demonstration of how heat efectively disappears according to the 2nd law of thermodynamics, and that cooling is autonomous than dependent.
The energy dissipated from the hypothetical 100% thermally isolated flask could be used for doing work in some other fields. I have speculated a bit about the thermal energy absorbed by the gravity field, for example; however, we don’t know a bit about it because we have not gone yet beyond our near surrounding cosmos. 🙂
Michael (19:36:03) :
I’m sorry, but is there not one scientist who can answer these questions for me?
Since when did they hang around WUWT?
REPLY: Lets see, Dr. Leif Svalgaard and Dr. Roy Spencer just to name two. You might want to check that snark rifle of yours before it jams on you. – A
Michael (18:58:20) :
“How many PPM of H2O are there in the atmosphere at any given time? What is the history?”
Since the CAGW’ers will never mention it, even googling for the information proved difficult. About a year ago I did some searching and the generally accepted one seems to be about
14,400 PPM for water vapor.
I don’t even know if there IS a history, if anyone has tried to determine it, or if it’s even possible to know.