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Trenberth talks about energy flows and global warming

What the science says...

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Trenberth's views are clarified in the paper "An imperative for climate change planning: tracking Earth's global energy". We know the planet is continually heating due to increasing carbon dioxide but that surface temperature sometimes have short term cooling periods. This is due to internal variability and Trenberth was lamenting that our observation systems can't comprehensively track all the energy flow through the climate system.

Climate Myth...

Trenberth can't account for the lack of warming

in one e-mail, a top "warmist" researcher admits it’s a "travesty" that "we can’t account for the lack of warming at the moment." As it happens, the writer of that October 2009 e-mail—Kevin Trenberth, a lead author of the warmist bible, the 2007 Intergovernmental Panel on Climate Change (IPCC) report—told Congress two years ago that evidence for manmade warming is "unequivocal." He claimed "the planet is running a ’fever’ and the prognosis is that it is apt to get much worse." But Trenberth’s "lack of warming at the moment" has been going on at least a decade. (Michael Fumento)

This has been most commonly interpreted (among skeptics) as climate scientists secretly admitting amongst themselves that global warming really has stopped. Is this what Trenberth is saying? If one takes a little time to understand the science that Trenberth is discussing, his meaning becomes clear.

If you read the full email, you learn that Trenberth is actually informing fellow climate scientists about a paper he'd recently published, An imperative for climate change planning: tracking Earth's global energy (Trenberth 2009). The paper discusses the planet's energy budget - how much net energy is flowing into our climate and where it's going. It also discusses the systems we have in place to track energy flow in and out of our climate system.

Trenberth states unequivocally that our planet is continually heating due to increasing carbon dioxide. This energy imbalance was very small 40 years ago but has steadily increased to around 0.9 W/m2 over the 2000 to 2005 period, as observed by satellites. Preliminary satellite data indicates the energy imbalance has continued to increase from 2006 to 2008. The net result is that the planet is continuously accumulating heat. Global warming is still happening.

Next, Trenberth wonders with this ever increasing heat, why doesn't surface temperature continuously rise? The standard answer is "natural variability". But such a general answer doesn't explain the actual physical processes involved. If the planet is accumulating heat, the energy must go somewhere. Is it going into melting ice? Is it being sequestered deep in the ocean? Did the 2008 La Niña rearrange the configuration of ocean heat? Is it all of the above? Trenberth wants answers!

So like an obsessive accountant, Trenberth pores over the energy budget, tallying up the joules accumulating in various parts of the climate. A global energy imbalance of 0.9 W/m2 means the planet is accumulating 145 x 1020 joules per year. The following list gives the amount of energy going into various parts of the climate over the 2004 to 2008 period:

  • Land:   2 x 1020 joules per year
  • Arctic sea Ice:   1 x 1020 joules per year
  • Ice sheets:   1.4 x 1020 joules per year
  • Total land ice:   between 2 to 3 x 1020 joules per year
  • Ocean:   between 20 to 95 x 1020 joules per year
  • Sun:   16 x 1020 joules per year (eg - the sun has been cooling from 2004 to 2008)

These various contributions total between 45 to 115 x 1020 joules per year. This falls well short of the total 145 x 1020 joules per year (although the error bars do overlap). Trenberth expresses frustration that observation systems are inadequate to track the flow of energy. It's not that global warming has stopped. We know global warming has continued because satellites find an energy imbalance. It's that our observation systems need to be more accurate in tracking the energy flows through our climate and closing the energy budget.

So what may be causing the discrepancy? As the ocean heat data only goes to 900 metre depth, Trenberth suggests that perhaps heat is being sequestered below 900 metres. There is support for this idea in a later paper von Schuckmann 2009. This paper uses Argo buoy data to calculate ocean heat down to 2000 metres depth. From 2003 to 2008, the world's oceans have been accumulating heat at a rate of 0.77 W/m2. This higher trend for ocean heat would bring the total energy build-up more in line with satellite measurements of net energy imbalance.

A subsequent study by Balmaseda, Trenberth, and Källén (2013) determined that over the past decade, approximately 30% of ocean warming has occurred in the deeper layers, below 700 meters.  This conclusion goes a long way to resolving the 'missing heat' discrepancy.  There is still some discrepancy remaining, which could be due to errors in the satellite measurements, the ocean heat content measurements, or both.  But the discrepancy is now significantly smaller, and will be addressed in further detail in a follow-up paper by these scientists.


So to summarise, Trenberth's email says this:

"The fact is that we can't account for the lack of warming at the moment and it is a travesty that we can't."

After reviewing the discussion in Trenberth 2009, it's apparent that what he meant was this:

"Global warming is still happening - our planet is still accumulating heat. But our observation systems aren't able to comprehensively keep track of where all the energy is going. Consequently, we can't definitively explain why surface temperatures have gone down in the last few years. That's a travesty!"

Skeptics use Trenberth's email to characterise climate scientists as secretive and deceptive. However, when one takes the trouble to acquaint oneself with the science, the opposite becomes apparent. Trenberth outlines his views in a clear, open manner, frankly articulating his frustrations at the limitations of observation systems. Trenberth's opinions didn't need to be illegally stolen and leaked onto the internet. They were already publicly available in the peer reviewed literature - and much less open to misinterpretation than a quote-mined email.

Intermediate rebuttal written by dana1981

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

Last updated on 14 July 2015 by pattimer. View Archives

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Further reading

Kevin Trenberth responds to the misrepresentation of his words in The truth about carbon dioxide, climate and the weather.


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Comments 51 to 53 out of 53:

  1. MA Rodger @48, Philippe Chantreau @49, Glenn Tamblyn@50,

    It seems to one that you are clearly confounding the amount of energy reaching a unit of surface (the fluxes in the IPCC's diagram that we are talking about here) with the amount of energy emitted per unit of surface of the source of the flux itself. Those are totally different concepts.

    In the IPCC's diagram, the solar flux coming in is not based on the unit of surface of the sun, it is based on the unit of surface of the Earth, that is, it is based not on the unit of surface of the source, but on the unit of surface of the target: it is directional, as all fluxes are.

    Many people have difficulties with fluxes, and from what you are writing, I understand that you are not familiar with them, but in the Earth's Energy Budget, we have to use them, because it is based on them, and we are reasonning with them, as all calculations here are done with fluxes.

    A flux in the Earth's Energy Budget is measured as a surface power density in time (W m-² for a given period), so there is no need to look at areas, geometries, and energy, as the surface power density is independent of the surface or geometry that is reached: it radiates some amount of energy per unit of surface in time.

    So the unit of surface of a flux is "per se": it is not the unit of surface of the object reached by the flux, it is independent of any particular geometry. Moreover, we are not dealing with the energy exchanged by a particular object per unit of its own surface: we are dealing with "outward", "directional" vectors of energy only here, transmitted by a blackbody.

    A blackbody receives input fluxes and emits output fluxes, such as the total input flux is equal to the total output flux by definition. Why ? Because for 1 unit of surface "per se", there has to be the same amount of energy emitted or received for a given period in order that as much energy comes in than goes out of the blackbody. Therefore the total input and total output have the same value.

    In other words, there is the same surface power density going in than going out per unit of time, and the total flux value is independent from the blackbody surface, only the number of fluxes, their value and their direction being regulated by the surface, but not their total value, in conformity with the definition of a blackbody radiation.

    In other words, each m2 reached by the total input flux will have the same amount of energy than each m2 reached by the total output flux, because a blackbody emits as much as it receives, independently of its own surface or geometry, which is another issue.

    So, in fluxes, the total input flux is equal to the total output flux for a blackbody, and it is quite different than the amount of energy emitted per unit of surface of the object itself.

    Therefore, coming back to the IPCC's Energy Budget, we add all inputs fluxes together for a blackbody on Earth's surface and we get 890 W m-² coming in.

    Because it is a blackbody, there has also to be an output flux of 890 W m-²: it is the same flux going out than going in, only the direction and the quantity and value of individual fluxes are changing, not its total value per m².

    Now, if that is clear, at thermal equilibrium, let's apply the Stefan-Boltzmann Law. We get for a blackbody emitting/receiving a flux of 890 W m-² a temperature of 80,8°C.

    What would be the input flux for the normal temperature of Earth, 15°C, as experimentally measured on Earth's surface ? Let's apply again Stefan-Boltzmann Law: we get a 390,9 W m-².


    IPCC's radiative model has a 65,8°C difference in temperature, and a 499,1 W m-² difference in radiative fluxes with experimental measures.

    IPCC's uncertainties concerning previsional temperatures are just a distraction compared to the huge difference existing between the radiative model and the experimental measures, the radiative model being at the basis of all prevision models.

  2. Ab @51 , 

    if your proposed 1m x 1m square "black body thermometer" is absorbing 890 watts in total, and is emitting 890 watts upwards . . . then its lower surface (facing the ground) must be emitting no watts at all.   In other words, the lower surface must have a temperature of absolute zero.

    Do you not find that to be a peculiarly interesting situation?

    Could be a source of energy for a perpetual motion machine . . . or a wonderful new way of generating unlimited electric power !

  3. ab,

    With you remaining oblivious to everything said to you and your continued spouting of the same nonsense, I would suggest your time here draws short. Perhaps you should think about returning wence you came. (I note you spent a week fulling up the borehole at RealClimate prior to arriving here at SkS.)


    [DB]  User ab has recused themselves from further participation here.

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