Another Inconvenient Pause

The Pause in global temperatures may be past, but here is another, longer Pause, and one that is much more difficult to explain: at ideal Australian sites, increasing greenhouse gas concentrations have led to a decrease in downwelling longwave radiation- the very opposite of expectations.

Basically, the theory behind the enhanced greenhouse effect is that the increase in concentrations of anthropogenic greenhouse gases leads to an increase in downwelling infra-red (IR) radiation, which causes surface warming.

Is there evidence for increasing downwelling IR in recent years, as atmospheric concentration of carbon dioxide has been rapidly rising?

The authors of Skeptical Science think so:

Surface measurements of downward longwave radiation

A compilation of surface measurements of downward longwave radiation from 1973 to 2008 find an increasing trend of more longwave radiation returning to earth, attributed to increases in air temperature, humidity and atmospheric carbon dioxide (Wang 2009). More regional studies such as an examination of downward longwave radiation over the central Alps find that downward longwave radiation is increasing due to an enhanced greenhouse effect (Philipona 2004).

Time for a reality check.

The links in the above quote do not work for me, so I use data available for Australia.

Greenhouse gas concentrations are measured at Cape Grim in north-west Tasmania.  According to the CSIRO,

The Cape Grim station is positioned just south of the isolated north-west tip (Woolnorth Point) of Tasmania. It is in an important site, as the air sampled arrives at Cape Grim after long trajectories over the Southern Ocean, under conditions described as ‘baseline’. This baseline air is representative of a large area of the Southern Hemisphere, unaffected by regional pollution sources (there are no nearby cities or industry that would contaminate the air quality).

Fig. 1:  Cape Grim Baseline Air Pollution Station (looking almost directly south)

c grim photo

Fig. 2:  CO2 concentration, Cape Grim.

co2 c grim

Fig. 3:  Methane concentration, Cape Grim.

ch4 graph

Fig. 4:  Nitrous oxide concentration, Cape Grim.

n2o graph

There is no doubt that concentrations of greenhouse gases have been increasing.  We should therefore expect to see some increase in downwelling longwave radiation.

Downwelling IR data are available from the Bureau of Meteorology which maintains a database of monthly 1 minute solar data from a network of stations around Australia, including Cape Grim.

What better location than Cape Grim to study the effects of greenhouse gas concentrations from month to month on readings of downwelling IR.  The instruments are within metres of each other under “baseline” conditions at a pristine site.

The data include 1 minute terrestrial irradiance (i.e. downwelling IR striking a horizontal surface) from which I calculated mean daily IR for each month.  To remove the seasonal signal, I calculate anomalies from monthly means.

Fig. 5:  Downwelling longwave radiation anomalies, Cape Grim.

ir over time capegrim

Oops! IR has been decreasing for the full length of the record, 20 years (May 1998 to June 2018).   And monthly IR anomalies plotted against monthly CO2 anomalies show a similar story:

Fig. 6:  Downwelling longwave radiation anomalies, Cape Grim.

ir vs co2 cgrim

In the most suitable location in Australia, from May 1998 to June 2018 there has been no increase in downwelling infra-red radiation, despite an increase of 41.556 ppm atmospheric concentration of carbon dioxide, 104.15 ppb of methane, and 14.472 ppb of nitrous oxide.

So what factors do influence downwelling IR and thus surface warming or cooling?  Together with solar radiation, that other greenhouse gas, H2O.  Gaseous H2O (humidity) and clouds formed of liquid and ice H2O are by far the major players in returning heat to the surface.

We see this in a plot of downwelling IR against cloudiness (from nearby Marrawa).

Fig. 7:  Downwelling IR anomalies vs Cloudiness, Cape Grim.

ir vs cloud capegrim

Daytime cloudiness (an average of observations at 9.00 a.m. and 3.00 p.m.) increases downwelling IR.  We have no data for night time cloudiness unfortunately.

To illustrate the irrelevance of carbon dioxide, here is a plot of anomalies of solar radiation (global irradiance), downwelling infra-red radiation, daytime cloudiness, and carbon dioxide concentration at Cape Grim over the past 20 years.

Fig. 8:  Anomalies of IR, Global Irradiance, CO2, and Daytime Cloud at Cape Grim 1998-2018

98 to 18 full range capegrim ir global co2 cloud anoms

And zooming in on 2008 to 2010:

Fig. 9:  Anomalies of IR, Global Irradiance, CO2, and Daytime Cloud at Cape Grim 2008-2010

98 to 18 2008 2010 capegrim ir global co2 cloud anoms

There is a feedback mechanism: cloudiness inhibits daytime temperature and increases IR and nighttime temperature; decreased cloudiness means decreased IR; but less cloud and higher daytime temperature will increase IR as well if sustained; and higher IR also increases daytime temperature.  Further, sustained decrease in global radiation due to increased cloud cools the surface, thus decreasing IR.

Carbon dioxide concentration changes have no detectable effect.

A desert location, where humidity is typically very low and rain and cloudiness very infrequent, would also be ideal for checking on downwelling IR from carbon dioxide.  Alice Springs in the central desert is such a location with available irradiance data.

At Alice Springs as well, since March 1995 downwelling IR has been decreasing.

Fig. 10:  Downwelling longwave radiation anomalies, Alice Springs.

ir over time alice

The relationship between cloud and IR is even more evident.

Fig. 11:  Anomalies of IR, Global Irradiance, CO2, and Daytime Cloud at Alice Springs 2008-2010

2008 2010 alice ir global co2 cloud anoms

Fig. 12:  Downwelling IR anomalies vs Cloudiness, Alice Springs.

alice ir v cloud

Cloudiness has an even greater influence on IR in desert than maritime locations.

TAKE AWAY FACT:-  For over 20 years, at what are arguably the most suitable sites in Australia, increasing greenhouse gas concentrations have had no detectable effect on downwelling longwave radiation.  Natural factors including cloudiness changes have vastly overwhelmed any such effect and have instead led to a decrease in downwelling longwave radiation.

That is indeed a most inconvenient pause.





To replicate these findings:

Go to

You will need to register with a username and password.  Then click on an irradiance observation station.  Select year and month.  Download the zip file, and open in your preferred application.  (I use Excel).  IR data are in Column W- the values are wattminutes of IR striking a horizontal surface of area one square metre.

My method:  Order the data in ascending order to remove null values.  Count the minutes of valid data and calculate the percentage valid of all possible minutes in that month.  (I discard months with less than 80% valid data.)   Divide the total minutes by 1,440 to convert to days.  Sum the valid data and divide by 60,000 to find kilowatthours; divide by the number of days to find the mean daily value; then multiply by 3.6 to convert to Megajoules.  Plot monthly values against time or carbon dioxide concentration.


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9 Responses to “Another Inconvenient Pause”

  1. ngard2016 Says:

    Ken you should get this on WUWT because this definitely needs a wider audience to shake things up.
    And I don’t mean just a link to your site , but a full blown post front and centre on WUWT and of course Jo and Jennifer as well.
    Please think about it, I’m sure they would be happy to agree to post it ASAP. But please don’t hesitate.

  2. Brett Keane Says:

    Amen to that. Great work!! Brett

  3. Steven Mosher Says:

    “Basically, the theory behind the enhanced greenhouse effect is that the increase in concentrations of anthropogenic greenhouse gases leads to an increase in downwelling infra-red (IR) radiation, which causes surface warming.”

    Ah not exactly.

    GLOBALLY, the effect works by raising the level at which the earth radiates to space. This means the earth will cool less rapidly than it would otherwise. The surface, on average, –which means not in every location– will radiate more to compensate and restore energy balance. Back radiation is more of an effect ( from this increased radiation ) than it is a cause of warming, despite what you might read in ‘popular’ accounts of the science. Increase GHGs raise the ERL, the effective radiating level, because we have a negative lapse rate, this means the earth will radiate from a higher and hence colder region. Since colder objects radiate more slowly, this means the earth will cool to space less rapidly than it would otherwise. You might also describe this as warming. In order to compensate for the reduction in outgoing energy, the surface will radiate more ( in IR) and you should, over time, GLOBALY AVERAGED, also see an increase in downwelling IR. Locally, over short periods, you may see variation in both the upwelling and downwelling, as with temperature, but globally averaged over long time periods it will trend up.

    Dont worry a lot of people are confused by the “downweling” IR explnation. here is a better explanation

    • kenskingdom Says:

      Thank you. The people confused by the “downwelling” IR explanation would include the authors of Skeptical Science. In Australia we find at these same sites Tmin increasing at the same time as IR is decreasing which is also confusing.

  4. Richard M Says:

    The Gero/Turner 2011 paper also found this same result in the US.
    There is another possibility as well. A reduction or change in the water vapor profile could also lead to less downwelling IR.

    Mosher is incorrect as well. The downwelling IR is a measure of the greenhouse effect. You can’t have it raise the ERL unless it increases as well. The warming would have to be from another cause.

  5. Brett Keane Says:

    You can tell the dillettantes in Physics when they show no comprehension of anything outside their ‘received’ beliefs. Maxwell trumps Mosher anytime and he realised Equipartition shifts energy to the less hampered pathways. Like buoyancy uplift and Latent Heat transfer to where energy can “see” Space. The Ideal Gas Laws even apply in parts of the Sun, certainly in its formation from c.2K gases etc. into ignited nuclear fireballs. Pressure, Mass, Gravity eg lapse rates formulae. So they do Rule here in the thicker band. Understanding is required of the different ‘nature’ of gases to get this. All to do with having room to move, enough to eliminate significant effects of large atoms vs smaller in the Quantum Statistical mellee.
    Photons on the other hand need atoms/molecules to radiate and the transmission-frequency is vastly slower than Kinetic vibration which thermalises energy for preference thusly. Buoyant expansion and rapid uplift took over aeons ago. Those vaunted photons cannot even radiate from solar/stellar cores for lack of molecular structures, so must rely on random walks to the convective layer, about 0.7 diameter of our sun. Tens of thousands of years.
    We keep saying: radiation is a weak Effect of its Strong Cause, Kinetic Energy vibrations of Matter. Else we would fry under the
    c.8000K solar Spectral Peak. Praise be for the -ve 4th power effect.

    AGW is just a crooked path to domination, ignoring gases’ lack of a surface to allow S-B to work for them. Having got away with Ozone so far, it was worth trying their next step on. Guess which side of the discussion is based on honesty? Brett

  6. Andrew Says:

    Thanks Ken. A good observation. Something to investigate more.

  7. barry Says:

    Have you considered ozone changes, Ken? I understand that can be a factor depending on prevailing winds over the Southern part of Australia. That and local changes in WV should be factored.

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