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Don't blame the sulphates

A new paper in Climate Dynamics examines the hypothesis that the indirect effects of aerosols (aka pollution) has been behind the hiatus/pause/thing-with-no-name/non-existent-thing that has, or has not, been affecting the global temperature average for the best part of two decades.

Andrew Gettelmann and colleagues focus on sulfate aerosols and plug revised forcing figures into climate models to see if this can bridge the gap to the temperature records. Unfortunately the answer seems to be a pretty firm "no".


Sulfate aerosol emissions increase globally from 2000 to 2005, and then decrease slightly to 2010. Thus the change in anthropogenic sulfate induced net global radiative forcing is small over the period. Sulfate ACI might be a contributor to the spatial patterns of recent temperature forcing, but not to the global mean ‘hiatus’ itself.


Of course there is always the possibility - or likelihood - that the models just can't simulate the cloud-aerosol interactions properly. Nevertheless, if they do then another explanation for the pause has been ticked off and the mystery deepens.

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Reader Comments (24)

This would seem to have implications for the modelling of the global temperature in the mid 20th century too.

Which is inconvenient as the models are trained on that period.

Oct 15, 2015 at 9:40 AM | Registered CommenterM Courtney

Of course there is always the possibility - or likelihood - that the models just can't simulate the cloud-aerosol interactions properly.

Hard for me to see why anyone - even the Met Office - would take climate models seriously. A climate model is inherently incapable of being validated. And an unvalidated model is, at best, nothing more than an illustration of somebody's hypothesis.

Yet 'climate science' often takes models for reality, talking about performing 'experiments' with models.

Oct 15, 2015 at 9:46 AM | Registered CommenterMartin A

Ho hum, the following from the recently published - Met Office Science Strategy: 2016-2021- Delivering science with impact

".......There are also other co-benefits of reducing some pollutants, such as black carbon and sulphate aerosols, on air quality and hence human, plant and animal health. But there are also risks that cleaning up those atmospheric aerosols that currently act to cool the planet might lead to acceleration in near-term warming in some parts of the world and interact adversely with regional climate variability. These sensitivities need to be understood more completely using a high-resolution climate model that can represent the effects of these pollutants on regional weather and climate patterns, as well as global mean temperature trends.

Likewise the role of cloud feedbacks in global climate sensitivity is still unresolved and requires greater understanding of the relationship between the atmospheric circulations and where clouds form. The water cycle dominates a lot of the uncertainty, especially at the regional level, and improving all aspects of the simulation of the water cycle from convection, cloud formation and precipitation to soil moisture and ocean salinity remains a high priority.Our strategy to increase the resolution of the physical climate model, to focus on the representation of cumulus convection and to understand the dynamics of the climate system is fundamental to addressing climate sensitivity and its ramifications......."

Pg 17

Oct 15, 2015 at 10:15 AM | Registered CommenterGreen Sand

Of course there is always the possibility - or likelihood - that the models just can't simulate the cloud-aerosol interactions properly. Nevertheless, if they do then another explanation for the pause has been ticked off and the mystery deepens.

And if they don't then the model output is totally flawed anyway.

Oct 15, 2015 at 10:21 AM | Unregistered CommenterGeckko

So much for needing 30 years data to evaluate climate trends! Once again they contradict themselves with their excuses.

Oct 15, 2015 at 10:32 AM | Unregistered CommenterJamesG

Good news that the consensus on settled science is still trying to figure out the cause of the pause, whilst other parts of the consensus on settled science, are still blaming the whole scam on CO2, neither of which fit the temperature records anyway.

Is it possible that before Paris, they could define what it is that they have agreed is' settled science'. It would make it easier for everyone else to understand why they even need to have a meeting.

Oct 15, 2015 at 10:32 AM | Unregistered Commentergolf charlie

Carl Sagan got his aerosol optical physics badly wrong so for 40 years, the modellers have felt secure because of 'globe dimming'.

In reality the sign of the 'AIE' is reversed and there has been 'global brightening', the real AGW!

The publication of these facts was blocked 4 years ago.

Oct 15, 2015 at 10:44 AM | Unregistered CommenterNCC 1701E

You have to admire the luck of these people , every time they find something new , which seems quite often for area that claims to be 'settled science ', it always seems to perfectly balance out the warming it 'would have occurred due to evil CO2' and that explains why the models which have totally failed to reflect reality are actually accurate.

The heads I win tails you lose approach , is one of the many aspects of climate 'science' which marks out its really quality .

Oct 15, 2015 at 10:48 AM | Unregistered Commenterknr

These sensitivities need to be understood more completely using a high-resolution climate model ...
Translates as "send more money".


The publication of these facts was blocked 4 years ago.
How very convenient! Can you provide us with some evidence (a) of the "facts"; (b) of the blocking thereof.
I used to be a fan of yours but enough already with the handwaving and the unsupported assertions, please.

Oct 15, 2015 at 10:55 AM | Registered CommenterMike Jackson

I thought it was a done deal: The heat is hiding deep down in the ocean where no one can see it. There, explained!

Oct 15, 2015 at 11:00 AM | Unregistered Commenterpax

Don't blame it on the sunshine
Don't blame it on the moonlight
Don't blame it on the good times
Blame it on the sulphates!

Oct 15, 2015 at 11:08 AM | Unregistered Commenteragn

The pause was caused by not adequately adjusting the temperature record.

Oct 15, 2015 at 11:13 AM | Unregistered Commenterson of mulder

@Mike: submitted to a well known climate change journal, returned in 48 hours; 'too many equations for our readership; resubmit to a Physics' journal', i.e kicked into the long grass. The Green Blob uses this journal for its propaganda.

The same observations but from satellites, and the same conclusions but without the theory, were made by G L Stephens in the US. He works with Trenberth and hasn't apparently been able to publish a peer reviewed article. See:

There is a second optical mechanism Sagan did not realise existed; the equation used in modelling is plain wrong.

Oct 15, 2015 at 11:50 AM | Unregistered CommenterNCC 1701E

And of course, there is also the possibility (probability>) that the models can not simulate anything.

Oct 15, 2015 at 11:57 AM | Unregistered Commentertoorightmate

When the models fail to correlate with observation, what to do ... (a) Tweek the models.
(b) Homogenize the temperature record. (c) Inoculate yr theory with a deux ex machina
factor. Cli-sci tricky methodology.

Oct 15, 2015 at 12:54 PM | Unregistered CommenterBeth Cooper

The pause is not a mystery to the Met Office:

"The recent pause in global warming has also challenged
our understanding of where the energy goes in the Earth
system and how the oceans take up heat. There is compelling
evidence that higher resolution is needed to represent
adequately the ocean circulations that act to sequester
heat away from the surface to the deeper ocean"

From the link given by Green Sand, 10:15 am comment above.

Oct 15, 2015 at 1:15 PM | Unregistered CommenterMikky

NCC ...
Thanks for the link. I'll put the cold towels on and try to make sense of it but I suspect the equations will be beyond me!

Oct 15, 2015 at 1:29 PM | Registered CommenterMike Jackson

@Mike: aerosols reduce the width of the frequency distribution of cloud droplet size. This reduces coarsening rate and limits the volumetric number density of the larger droplets. Mie analysis shows forward scattering is proportional to the 6th power of droplet size. More, larger droplets cause more internal reflection.

Sagan falsely claimed Mie scattering causes hemispheric albedo to asymptote at 1.0. It is really 0.5. A thundercloud with 0.9 albedo backscatters 80% in the first few 100 metres. Add in half of 20% from diffuse scattering and you reverse the IPCC claims that smaller droplets give higher albedo. This process explains Milankovitch amplification, the Arctic melt freeze cycle and real AGW from Asian industrialisation - lower Pacific cloud albedo; the effect saturated 15 years ago.

Oct 15, 2015 at 1:40 PM | Unregistered CommenterNCC 1701E

And what should be obvious to every thinking person - if there are such things any more - is that the more they search OUTSIDE their model for an explanation to "the pause," the more they are admitting that the model does not predict, er, forecast climate change at all.

Basically, what they are doing is "painting a house" with a color. The color is supposed to be a specific shade of blue, but as the paint goes on, the color appears to be a greenish hue. So what they are doing are looking at the surface they are painting, the pollution in the air surrounding the house, the type of grass that is growing in the lawn, checking to see if perhaps they used the wrong surfacing material in the driveway, but never, EVER checking the paint to make sure it is actually the color they thought they got. To a thinking person, the first place you would check is the paint.

In the case of the models, that is what they need to do - check the models, rework the theory behind them, and create a better model. Problem with that is that the output wouldn't be scary enough to make the human race depopulate to save Gaia, and technology has pushed warfare to the state where the ultra rich might not be able to survive a war capable of forcing the depopulation, and they are nervous about using a GM virus to do it since they couldn't control natural evolution of the virus once it was released.

Oct 15, 2015 at 2:02 PM | Unregistered CommenterTom O

AFAIK only Hansen & Schmidt argued that the pause was caused by aerosols. And now their ex-NASA colleague, Shindell, reveals they were wrong. Much ado about nothing.

Oct 15, 2015 at 4:09 PM | Unregistered CommenterJamesG

Tom O, don't be stupid, climate scientists are just trying to find the correct shade of greenish red house paint, to match the reddish green, they have to achieve. Not easy for the numerically challenged, colour blind, being guided by a dogma on a short lead.

Oct 15, 2015 at 5:16 PM | Unregistered Commentergolf charlie


too many equations for our readership; resubmit to a Physics' journal<\blockquote>

So have you resubmitted to a physics journal?

Oct 15, 2015 at 8:10 PM | Unregistered CommenterThinkingScientist

Reduced aerosols did cause a small amount of (real) late 20th century warming, but mostly reduced aerosols caused a spurious increase in minimum temperatures as reduced lowlevel aerosols and aerosol seeded clouds allowed more early morning solar radiation to reach the surface, causing earlier and higher minimum temperatures. Incorrectly interpreted as warmer nights.

Oct 15, 2015 at 11:58 PM | Unregistered CommenterPhilip Bradley

Don't blame it on the sunshine
Don't blame it on the sulphates,
Don't blame it on the water
Blame it on see-oh-tu

The Jacksons, Blame it on the Boogie, if you want a novelty song for Paris

Oct 16, 2015 at 1:54 AM | Unregistered Commentergolf charlie

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