‘Models don’t account for clouds’—Clouds are complex and uncertain, but unlikely to stop warming 6

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: Clouds are a large negative feedback that will stop any drastic warming. The climate models don't even take cloud effects into account.

Answer: All of the atmospheric global climate models used for the kind of climate projections synthesized by the IPCC take the effects of clouds into account. You can read a discussion about cloud processes and feedbacks in the IPCC TAR.

It is true, however, that clouds are one of the largest sources of uncertainty in the GCMs. They are complicated to model because they have both positive feedbacks, preventing surface heat from escaping back into space, and negative feedbacks, reflecting incoming sunlight before it can reach the surface. The precise balance of these opposing effects depends on time of day, time of year, altitude, size of the water droplets and/or ice particles, latitude, current air temperature, and size and shape.

On top of that, different types of clouds will interact, amplifying or mitigating one another's effects as they coexist in different layers of the atmosphere. There are also latent heat considerations -- water vapor condenses during cloud formation and precipitation events, and water droplets evaporate when clouds dissipate.

The ultimate contribution of clouds to global temperature trends is highly uncertain, but according to the best estimates is likely to be positive over the coming century. There is no indication anywhere that any kind of cloud processes will stop greenhouse-gas-driven warming, and this includes observations of the past as well as modeling experiments.

Former musician, turned tree planter, turned software engineer. Same old story…

I have been blogging about climate change since 2006 at A Few Things Ill Considered.

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  1. Zarkov Posted 7:26 pm
    18 Nov 2006

    Clouds = Rain>> according to the best estimates is likely to be positive over the coming century  >>
    Lets hope so, but clear sky days seem to be increasing.  We could do with much more rain.

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  2. SMLowry's avatar

    SMLowry Posted 9:45 am
    19 Nov 2006

    More rain?Depends on where you are. This year and last, in New England, have been among the wettest on record. This year, so far, we've had a good 20 to 25 inches more rain than "normal", which is substantial! And we've also had many cloudy days. This past spring, for example, it rained on (I believe) 21 days in May and some of the days that didn't rain were cloudy. Luckily we did get some sun during the summer. But this gray, rainy spring seems to be the trend. And warmer winters, more rain, less snow. Then there are other places where rain is desperately needed.

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  3. gzuckier Posted 7:41 am
    04 Jul 2007

    "No clouds" global warming theoryThis might be a good place to note the "cosmic rays cause clouds; clouds reflect the sun; we are going though fewer cosmic rays now, therefore fewer clouds, therefore more warming" theories of Svensmark et al. Aside from the general haggling about the accuracy of the model and whether there is any correlation at all, and the question of how a 14 million year cycle can cause rapid warming over a couple of decades, there is this basic problem: the current measurements show a greater effect for nighttime temperatures than daytime temperatures, and a greater effect at the poles, which are more covered in snow and ice than the rest of the earth and therefore already more reflective; the opposite of what any "clouds reflect the sun, less clouds means more cooling" theory would predict.

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  4. Louise L Posted 7:10 am
    26 Feb 2008

    WellI wouldn't like the clouds to dissapear for good, I believe they are doing us some good.

    Louise, Freelancer currently working on the lose 50 pounds fast project.

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  5. rcglinsk Posted 4:56 am
    24 Mar 2008

    CloudsUmmm....  aren't you basically saying here "yeah, properly modeling clouds is about as important as it gets to understanding climate, and no, it's not currently done well at all."  That's not much of a response; more of a admission.  

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  6. Dan Halen Posted 7:29 am
    02 Jul 2008

    It's an explanation, not an admissionWhat he's probably getting at is this:  I make a computer model, I have various measurements I take or assumptions I make that lead to uncertainty, some of the uncertainties are small, others large.  I carefully propagate my error mathematically through the calculation at the end and publish my results.  Let's say they boil down to, oh say something like, I dunno, a temperature.  The number is published as 5C +/- 2C.  Of the 2C worth of uncertainty about 80% is due to a single rather uncertain measurement or factor.  Thus I say "factor A accounts for the majority of uncertainty in this value".  This does NOT mean that my whole experiment or model in useless or invalid.
    Of course the best test of a computer model is to match it against the real world.  This has been done through hindcasting.  You take known historical data on CO2, pollutants, etc... and run the GCM.  You then see how well the temperatures it produces matches what happened in the real world.  It turns out that the current GCMs are quite good at matching with known historical data in fact.  If the model clouds were behaving much differently than real ones this would not have been possible.
    You also seemed to have missed the bit at the end where he told you that nothing in the past indicates that clouds will save us.  We've seen massive warming lately along with massive output of GHGs.  The clouds haven't saved us yet, why would anyone think they will suddenly start doing so?  And where were the clouds during the paleoclimactic periods that were very warm?  Napping on the job again.

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Series Intro
'There is no evidence' -- Yes, there is 59
'Mauna Loa is a volcano' -- CO2 rise is measured on top of a volcano! 8
'Warming is due to the Urban Heat Island effect' -- No, it isn't 25
'One hundred years is not enough'--Yes it is 18
'The scientists aren't even sure' -- No scientist ever is 33
'One record year is not global warming'--Luckily, there are plenty more years to consider 19
'Glaciers have always grown and receded'--A few glaciers melting does not mean global warming 14
'The temperature record is unreliable'--But temperature trends are clear and widely corroborated 8
'It's cold today in Wagga Wagga'--Weather and climate are different 2
'The satellites show cooling'--No, they don't 15
'What about mid-century cooling?'--No one said CO2 is the only climate influence 11
'Antarctic ice is growing'--Well, probably not, but even if it were, we are not off the hook 8
'Global warming stopped in 1998'--Only if you flagrantly cherry pick 170
'But the glaciers are not melting'--Except ... they are! 3
'Antarctic sea ice is increasing'--Yes, but ... 14
'Sea level in the Arctic is falling'--Sea level is a surprisingly complicated thing 11
'Climate sensitivity is not very high'--Thermal inertia of the oceans means the jury is still out 2
'Some sites show cooling'--But you can't draw global conclusions from individual sites 0
'Global warming is a hoax'--I wish James Inhofe were just a hoax ... 12
'There is no consensus'--If this is not consensus, what would consensus look like? 109
'Position statements hide debate'--True enough, but that is not the whole picture 5
'Consensus is collusion'--Is climate science maturing, or should we reach for our tinfoil hats? 8
'Peiser refuted Oreskes'--In a poor piece of work that has been retracted by its author 4
'Models don't account for clouds'--Clouds are complex and uncertain, but unlikely to stop warming 6
'Climate models are unproven'--Actually, GCM's have many confirmed successes under their belts 13
'Aerosols should mean more warming in the south'--More North. Hemisphere warming is well-understood 1
'We can't even predict the weather next week'--But weather is not climate 11
'Chaotic systems are not predictable'--Sure, but who says climate is chaotic? 13
Understanding what is happening right under our noses does not require paleoclimate perfection 1
'They predicted global cooling in the 70s'--But that didn't even remotely resemble today's consensus 29
'Hansen has been wrong before'--Maybe, but not about the climate! 13
'It was warmer during the Holocene Climatic Optimum'--This period was not global and not like today 4
'The Medieval Warm Period was just as warm as today'--Repeating this point does not make it true 216
'Greenland used to be green'--Don't judge a book by its cover, much less a land by its name 23
Yes, the last ice age started thawing over 20,000 years ago, but that stopped a long time ago 5
'The hockey stick is broken'--Well, no ... but who's playing hockey anyway? 6
'Vineland was full of grapes'--Or was it an early advertising campaign? 4
'Global warming is part of a natural cycle'--This idea is one short step above appealing to magic 39
'Mars and Pluto are warming too'--No they aren't -- and what if they were? 24
'Volcanoes emit more CO2 than humans'--Not even close ... 31
'The null hypothesis says warming is natural'--An inappropriate test, and one that would fail anyway 4
'Climate is always changing'--That doesn't mean it isn't different today 5
'Natural emissions dwarf human emissions'--But emissions are only one side of the equation 5
'The CO2 rise is natural'--No skeptical argument has been more definitively disproven 12
'We are just recovering from the LIA'--Why should we expect this to happen? 4
'Climate scientists dodge the subject of water vapor'--No, they really don't 4
Water vapor is indeed a powerful greenhouse gas, but there is plenty of room for CO2 to play a role 29
There is no proof in science, but there are mountains of evidence 78
'CO2 doesn't lead, it lags'--Turns out CO2 rise is both a cause and an effect of warming 43
'Geological history does not support CO2's importance'--Just not true 0
'Historically, CO2 never caused temperature change'--Not so 19
'It's the sun, stupid'--Very bright, yes, but not getting brighter 18
The problem is not how high the temperature may go, but how fast it is changing 14
'Kyoto is a big effort for almost nothing'--Kyoto is only in its first phase 16
China and India have joined Kyoto, they just have different obligations, as is morally appropriate 3
'Climate change mitigation would lead to disaster'--Not really, but this may be lesser of two evils 6
Only if you ignore fossil fuel emissions 10
In 2008, did temperatures drop as much as they rose over the whole 20th century? 71
Is the IPCC so wrong their theories contradict a basic laws of physics? 23
Is the American Physical Society a crack in the climate change consensus? 3
Summer ice in the Arctic has recovered--Was the Arctic ice retreat a climate anomaly? 7
'Global warming comes from within'--Is heat at the Earth's core the real cause of global warming? 10
Was there another breathless announcement of another phony record, and another quiet retraction? 1
Hansen wants the skeptics thrown in jail--Did James Hansen really want to try the climate skeptics? 6
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