Guest post by Bart Verheggen, Department of Air Quality and Climate Change , Energy research Institute of the Netherlands (ECN)
In Part I, I discussed how aerosols nucleate and grow. In this post I’ll discuss how changes in nucleation and ionization might impact the net effects.
Galactic cosmic rays (GCR) are energetic particles originating from space entering Earth’s atmosphere. They are an important source of ionization in the atmosphere, besides terrestrial radioactivity from e.g. radon (naturally emitted by the Earth’s surface). Over the oceans and above 5 km altitude, GCR are the dominant source. Their intensity varies over the 11 year solar cycle, with a maximum near solar minimum. Carslaw et al. give a nice overview of potential relations between cosmic rays, clouds and climate. Over the first half of the 20th century solar irradiance has slightly increased, and cosmic rays have subsequently decreased. RC has had many previous posts on the purported links between GCR and climate, e.g. here, here and here.
The role of ions
The role played by ions relative to neutral (uncharged) molecules in the nucleation process is still very much under discussion. For instance, based on the same dataset, Yu and Turco found a much higher contribution of ion induced nucleation (to the total amount of particles produced) than Laakso et al did. Evidence for a certain nucleation mechanism is often of an indirect nature, and depends on uncertain parameters. Most literature points to a potential importance of ion induced nucleation in the upper troposphere, but the general feeling is that neutral pathways for nucleation (i.e. not involving ions) are likely to be dominant overall. Most field studies, however, have been performed over land, whereas over the open ocean nucleation rates are generally lower due to lower vapor concentrations. In theory at least, this gives more opportunity for ion induced nucleation to make a difference over the ocean (even though the ion production rate is smaller).
The ion production rate (increasing with altitude from ~10 to ~50 ion pairs per cubic centimeter per second over land) sets a limit to what the particle formation rate due to ion induced nucleation can be. Based on his model for ion induced nucleation, Yu found that at low altitude, the number of particles produced is most sensitive to changes in cosmic ray intensity. At first sight, this may be a surprising result in light of the increasing cosmic ray intensity with increasing altitude. The reason is that high aloft, the limiting factor for particle formation is the availability of sulfuric acid rather than ions. Above a certain GCR intensity, increasing ionization further could even lead to a decrease in ion induced nucleation, because the lifetime of ion clusters is reduced (due to increased recombination of positive and negative ions). In contrast, at low altitude particle formation may be limited by the ionization rate (under certain circumstances), and an increase in ionization leads to an increase in nucleation.
How important is nucleation for climate?
Different modeling exercises have been performed to investigate this question. The strong dependency on input data and assumptions used, e.g. relating to primary particle emissions and nucleation parameterizations, and the different sensitivities tested, hampers an overall assessment. However, it is clear that globally, nucleation is significant for the number of cloud condensation nuclei (CCN) e.g. in the absence of boundary layer nucleation, the number of CCN would be 5% lower (Wang and Penner) or 3-20% lower (Spracklen et al.), and in a recent follow up study, they concluded that the number of cloud droplets would be 13-16% lower (in 2000 and 1850, respectively). Pierce and Adams took a different approach and looked at the variation of predicted number of CCN as a result of using different nucleation schemes. The tropospheric number of CCN varied by 17% (and the boundary layer CCN by 12%) amongst model runs using different nucleation rate parameterizations. Note that the globally averaged nucleation rates differed by a factor of a million (!).
It should be noted that the sensitivity of the number of CCN to nucleation depends greatly on the amount of primary emissions and secondary organic aerosol (SOA) formed. These are very uncertain themselves, which further limit our ability to understand the connection between nucleation and CCN. If there are more primary emissions, there will be more competition amongst aerosols to act as CCN. If more organic compounds partition to the aerosol phase (to form SOA), the growth to CCN sizes will be quicker.
Locally, particle formation has been observed to contribute significantly to the number of CCN; the second figure in Part I gives an example of freshly nucleated aerosols which grew large enough to influence cloud formation. Kerminen et al observed a similar event, followed by activation of part of the nucleated aerosols into cloud droplets, thus providing a direct link between aerosol formation and cloud droplet activation.
How important are cosmic rays for climate?
At the recent AGU meeting (Dec 2008), Jeff Pierce presented results on the potential effects of GCR on the number of CCN (their paper at GRL (sub. required)). Two different parameterizations for ion induced nucleation were used (Modgil et al and an ‘ion-limit’ assumption that all ions go on to form a new particle). They ran their model with both high and low cosmic ray flux, simulating conditions during solar maximum and minimum, respectively. This happens to be comparable to the change in cosmic ray flux over the 20th century (mostly confined to the first half), and amounts to a 20% change in tropospheric ion production. With both mechanisms of ion-induced nucleation, this leads to a 20% change in globally averaged particle nucleation, but only to a 0.05% change in globally averaged CCN. The authors concluded that this was “far too small to make noticeable changes in cloud properties based on either the decadal (solar cycle) or climatic time-scale changes in cosmic rays.” To account for some reported changes in cloud cover, a change in CCN on the order of 10% would be needed. More studies of this kind will undoubtedly come up with different numbers, but it’s perhaps less likely that the qualitative conclusion, as quoted above, will change dramatically. Time will tell, of course.
The bottom line
Freshly nucleated particles have to grow by about a factor of 100,000 in mass before they can effectively scatter solar radiation or be activated into a cloud droplet (and thus affect climate). They have about 1-2 weeks to do this (the average residence time in the atmosphere), but a large fraction will be scavenged by bigger particles beforehand. What fraction of nucleated particles survives to then interact with the radiative budget depends on many factors, notably the amount of condensable vapor (leading to growth of the new particles) and the amount of pre-existing particles (acting as a sink for the vapor as well as for the small particles). Model-based estimates of the effect of boundary layer nucleation on the concentration of cloud condensation nuclei (CCN) range between 3 and 20%. However, our knowledge of nucleation rates is still severely limited, which hampers an accurate assessment of its potential climate effects. Likewise, the potential effects of galactic cosmic rays (GCR) can only be very crudely estimated. A recent study found that a change in GCR intensity, as is typically observed over an 11 year solar cycle, could, at maximum, cause a change of 0.1% in the number of CCN. This is likely to be far too small to make noticeable changes in cloud properties.
309 Responses to "Aerosol effects and climate, Part II: the role of nucleation and cosmic rays"
Staffan Sjogren says
Thanks Bart for a nice summary ;)
So I wonder, if up to 20% of the particles grew from nucleation size,
where do the other 80-97% of the number of climate relevant particles come from? Or did I misunderstand something?
What would the preindustrial aerosol load thus look like? To compare with current anthropogenic aerosol related climate effects?
Cheers, Staffan, exPSI
Edward Greisch says
The take-home message is still the same: “It is the CO2 that is causing the climate change.” Denialists: There are no straws for you to grab here. A little uncertainty at the edge is not an excuse for nonsense.
Ray Ladbury says
Bart, Excellent summary on a subject near and dear to my heart (terrestrial effects of cosmic rays). I believe it puts paid to the assertions from the denialosphere that scientists are emphasizing CO2 exclusively. Clearly there’s much still to learn here, but it is gratifying to see the progress that is being made.
Wilmot McCutchen says
There is also a black carbon effect, which is additive to CO2. Soot particles in the atmosphere may be too small to have a shading effect. Such tiny particles absorb energy, acting as little heaters for air molecules around them. Soot might also deposit on the polar ice, reducing its albedo. Perhaps Bart will post a Part III refuting the recent denialist talking point that scrubbing aerosols is reducing the global cooling effect (by shading) of aerosols, which might offset the global warming effect of CO2 and other greenhouse gases.
Richard J Jordan says
Very informative! Looking forward to next article in series.
R Keene says
So why the strong correlation between climate and sunspot count over the last 400 years?
[Response: What strong correlation between climate and sunspot count over the last 400 years? – gavin]
This guy is much more eloquent than most….and he is from auz, where they know about what it is like on the curve of climate change…
Poor prognosis for our planet
Every patient with an incurable illness will ask how long they have to live. The answer goes something like this: “No one can say how long you may live, because every individual is different, but focus on the changes you observe and be guided by those. When things start changing for the worse, expect these changes to accelerate. So the changes that have occurred over a year may advance by the same degree in a few months, then in weeks. And that is how you can judge when the end is coming.”
Apply that thinking to climate change. When An Inconvenient Truth opened in 2006 it was generally supposed we had a window of two or three decades to deal with climate change. Last year that shrank to a decade. Last month Australia’s chief scientist, Penny Sackett, told a Canberra gathering that we have six years to radically lower emissions, or face calamitous, unstoppable global warming.
Six years. Given that this problem is usually described as a process unfolding over centuries, how can it be that things have spun out of control in such a short time?
Climate change is often described as linear decline followed by some kind of distant “tipping point”. But consider these statistics: in 1979 Arctic sea ice cover remained above 7 million square kilometres all summer; from 1989 it was consistently above 6 million; in 2002 above 5 million; since 2007 above 4 million. I read recently we may have reached a tipping point and the ice will be gone in 20 years. But there is no tipping point – a curve is always tipping, and each new finding redraws the curve.
If this year’s figure comes in under 4 million square kilometres the patient could be dead inside five years, and ships will be crossing the North Pole in September 2014.
I do believe the evidence. Which leads me, personally, to the bleak conclusion that the human race is stuffed. The current financial crisis is merely the curtain raiser to a grand opera of social and ecological collapse. Our children – forget our grandchildren, I’m talking about my own kids, aged 14, 11 and 9 – are going to live in a world in which major cities are flooded, fertile plains become deserts, populations run out of food and water, rivers run dry, fishing grounds become dead zones, our rainforests and living coral reefs become curiosities of history.
Of course, there is a great problem with declaring that point of view because one immediately becomes labelled as a mad Cassandra spouting visions of the apocalypse.
The parlous state of our planet’s health could not be more evident, and still nothing has happened, except that eminent scientists like Jim Hansen have been driven to join the barricades. Demonstrating last month in Britain for a complete moratorium on new coal-fired power stations he said with typical understatement: “The democratic process doesn’t quite seem to be working.”
We would rather watch TV shows glorifying some brainless criminal underclass than engage in meaningful civil disobedience. Since Greenpeace went corporate there has been a global shortage of eco-warriors, and most scientists lack the mongrel element to start a revolution.
The rest of us are less evolved; my suspicion is that most of us still don’t get it. Because here’s the paradox: wherever you look in the natural world the message of exponential change is reinforced, yet humans have a weird predisposition to see change as linear. I’m guessing this is a throwback to the caveman days when, if someone threw a rock or a spear at you, it was sensible to assume that the missile would keep coming at a constant speed. Strangely, we unconsciously apply the same neanderthal logic to our understanding of ageing, birth and climate change.
John H. says
“Denialists: There are no straws for you to grab here. A little uncertainty at the edge is not an excuse for nonsense.”
,neglects to place in context this latest “uncertainty”.
Like many others this latest “uncertainty” should not be considered in a stand alone observation.
The proper context is this new “uncertainty” bolsters the totality of many critical uncertainties and indeed fatally flawed components to AGW.
At some point the current level of confidence in AGW should not be sustained if intellectual honesty and science are to remain connected.
If I may be so bold as to ask, under what scenario does the ultimate unfolding of AGW ever occur having been so adamantly championed as a certainty by so many?
Do we actually have to wait for decades of additional measurement and observation?
How are AGWers ever to back out of something they are so comitted to?
“At some point the current level of confidence in AGW should not be sustained if intellectual honesty and science are to remain connected.”
Why? This isn’t an error in the theory of AGW, it’s an uncertainty in the detail of the effects of climate change.
This is like saying just because I can’t weigh myself to the gram, the theory of gravity will have to be rethought.
And uncertainty means “you don’t know the effects”. Which could be
a) it makes it better (what you seem to say)
b) it makes it worse (which you seem to be unable to accept)
Now, what do you know about uncertainties and these uncertainties in particular that lets you know it will be only a mitigation against problems of climate change?
I shall not be holding my breath, however.
[Response: What strong correlation between climate and sunspot count over the last 400 years? – gavin]
The strong correlation that he’s been told is there.
He hasn’t looked for it, because that would be, like, skeptical of those claims…
Bart Verheggen says
Hi Staffan, nice to hear from you!
Good question you’re asking (sharp as ever). Bear in mind that some studies looked at the effect of nucleation on cloud droplets (not CCN) and some looked at boundary nucleation only, so the effect of nucleation over the whole troposphere (and lower stratosphere) on CCN may be larger than the numbers stated. The outcome also seems dependent on the way the question is addressed, since there are many dependencies at work, e.g. how many nucleated particles act as CCN is dependent on how many primary emitted particles there are, and vice versa. It’s a competition out there.
Perhaps some of the global aerosol modelers can also weigh in on this question.
Admittedly, the relatively small contribution of nucleation to the CCN budget surprised me as well. I remember a presentation a few years back about how little impact nucleation had on the number of CCN based on a regional model simulation. I didn’t believe any of it at first. Because in some way it meant that I waisted my entire PhD studying something that in the end didn’t matter much. Now that’s put a little strong, but in hindsight such professional deformation may explain why some geologists aren’t convinced of the seriousness of current climate changes (just look at the Cretaceous), or why some meteorologists just don’t believe climate models (just look at the weather forecast).
John H. wrote: “If I may be so bold as to ask, under what scenario does the ultimate unfolding of AGW ever occur having been so adamantly championed as a certainty by so many?”
If I may be so bold as to reply, with all due respect, what you really need to understand is that you don’t have a clue what you are talking about, and that you are not going to interest, let alone impress, anyone with arrogant comments based on ignorance.
Ray Ladbury says
So, John H., have you ever even met any scientists… because it’s kind of hard to credit you with any knowledge of science when you think knowing uncertainties is a bad thing.
Did you ever wonder that maybe your utter ignorance of science might not be shared by those who devote, oh, say 20-40 years of their lives to its study?
Here’s how the game is played. We have a theory of Earth’s climate that really does a very good job describing trends we see in the paleoclimate and the modern climate. We don’t understand absolutely every aspect, but we do understand enough to realize that the UNCERTAINTIES are not going to negate what we do understand. The humans are behind recent warming is an inescapable consequence of that theory. Don’t like that conclusion and want to do something about it? Simple, all you have to do is come up with a better theory. Go ahead. We’ll wait.
[So, anybody know any good jokes. We could be here awhile.]
Ike Solem says
Re#1, The record of tropical dust is due to work carried out on tropical glaciers, see:
Records of large volcanic eruptions are also present in ice cores:
Someone ought to tell the folks over at Stanford’s SLAC National Accelerator Laboratory to incorporate the more recent studies into their “Visitor Center” information packets:
Stanford and DOE – they are also big backers of carbon capture and sequestration. They say that 90% of carbon emissions from coal plants can be captured this way – not that they have any working prototypes to support such claims.
Is there a connection between the SLAC view of cosmic rays and climate, the DOE’s support for coal, and Stanford’s Exxon-funded Global Climate and Energy Program? Interesting question, isn’t it?
Al Z says
“What strong correlation between climate and sunspot count over the last 400 years?” So Gavin, I take it you’ve never seen “The Great Global Warming Swindle”?
Maybe this link will clear things up: http://folk.uio.no/nathan/web/statement.html
Hank Roberts says
Don’t let replying to trolls take over the topic folks.
Focus. Dr. Verheggen is here teaching. Let’s learn.
Jeff Pierce says
In response to Bart Verheggen’s comment (#11). Nucleation research is still very important for climate, so don’t be too bummed out. A 20% uncertainty in CCN in the boundary layer due to uncertainty in nucleation still leads to an indirect effect uncertainty on the order of 1 W m-2, a very big deal!
[Response: I take it that this is for the anthropogenic indirect effect over the 20th C? – gavin]
Jeff Pierce says
Sorry, I was not precise. If you were to change CCN by 20% in the boundary layer, the global cloud shortwave forcing would change on the order of 1 W m-2 (either during pre-industrial times or present day). See Seinfeld and Pandis, Atmospheric Chemistry and Physics, page 1176 in the first edition and 1083 in the second edition. These ~10-20% uncertainties in CCN are what was described in the “How important is nucleation for climate?” section, not the smaller CCN uncertainties associated with changes in cosmic rays described in the “How important are cosmic rays for climate?” section.
My main point is that nucleation research in general is still necessary to increase our understanding of aerosol-cloud interactions.
Timothy Chase says
Hank Roberts wrote in 16:
Thank you for the reminder, Hank.
Bart Verheggen says
Wilmot McCutchen (4): You’re right about some particles (soot) causing warming and some (most others) causing cooling. The net global effect is thought to be cooling. There are some recent papers pointing out that the aerosol burden over Europe has decreased over the past few decades, probably having contributed to the observed (strong, local) warming. (Over Asia the aerosol burden is still increasing, and over the US I think no strong trends were detected – I don’t have the reference by hand though). The fact that some folks try to put a spin on such patterns to suit a predetermined notion doesn’t make the observed patterns untrue.
Bart Verheggen says
Hi Jeff (17, 18)
I agree with you that “that nucleation research in general is still necessary to increase our understanding of aerosol-cloud interactions.” Perhaps I expressed myself too strongly in my previous comment (#11). I meant to convey the natural tendency to want your own area of work to matter for the big picture.
Bart Verheggen says
Ike Solem (#14),
I don’t take great issue with what Stanford writes about their accelerator. It’s quite carefully worded (e.g. “But it is at least possible that cosmic rays could have something to do with it.”) without outlandish claims in the part you cite; though indeed, in total it gives a somewhat uncritical view of the topic. Remember that they too would like their area of work to matter for the big picture (but I start repeating myself).
Alan Millar says
#13 Ray Ladbury
” We have a theory of Earth’s climate that really does a very good job describing trends we see in the paleoclimate and the modern climate. ”
But the models relating to this hypothesis are completely wrong for the period 1940 – 1970.
The integrity of the hypothesis and the models are maintained only by stitching another hypothesis onto the models ie that aerosols caused the cooling effect.
However, this hypothesis remains completely unproven as far as I am aware. Without proof of this hypothesis then the CO2 hypothesis must also remain unproven based on data from the start of the 20th century to date. Unless you can close the disconnec,t between observed data and the models, with a largely proven hypothesis then no way can you declare the science or hypothesis as settled.
I would have thought that if it was aerosols causing the cooling then there should be a clear sign that areas that were high producers of aerosols during the period 1940 – 1970 should display a larger cooling trend than other areas given the known localised cooling effect of certain aerosols.
Is there any evidence for this? Without this correlation I would have thought the aerosol hypothesis would fall at the first fence.
Perhaps Dr Verheggen can answer this.
David B. Benson says
Bart Verheggen — Very clear and quite helpful!
But I found “over the open ocean nucleation rates are generally lower due to lower vapor concentrations.” counter-intuitive. I would have thought that over oceans water vapor concentrations would be higher. Would you explain this subtle point?
“But the models relating to this hypothesis are completely wrong for the period 1940 – 1970. ”
They are? How?
Dirty smoke and acid rain would have made a bigger contribution to climate than CO2 since we’d hardly started using oil (the UK navy only started usin oil instead of coal around 1910, IIRC) and coal had always at that time been quite hard to remove (try working a steam engine on the coal face…).
So how were the models completely wrong for that period?
“So Gavin, I take it you’ve never seen “The Great Global Warming Swindle”?”
Ah, you mean the unscientific biased piece that had to apologise because it edited and put out of context so many of the people who spoke on it just to make it look like there was a controversy.
It was about as scientific as the movie The Day After Tomorrow.
C02 has just gone up to 389 from 386 a few days ago.
Hank Roberts says
Abi, it hasn’t “just gone up” — that’s just a new data point there. Click the link for the source; you’ll see:
” The last year of data are still preliminary, pending recalibrations of reference gases and other quality control checks.”
Too bad. I thought for a moment this proved we could attribute the change to the Easter Bunny ….
Hank Roberts says
Dr. Verheggen, I haven’t yet read most of the articles you link at the top, apology if this is covered; I will try to catch up. I recall mention a while back that bacteria and viruses over the ocean are involved (and it was only recently we learned that there is some astonishing number of viruses in any sample of sea water). This is one link grabbed quickly that might lead into that area.
HAL :: [hal-00297700, version 1] High-resolution ice nucleation …
Even though studies of Arctic ice forming particles suggest that a bacterial … Our experiments revealed that all sea-ice isolates and the virus nucleated ice at temperatures very close to … Sciences of the Universe/Ocean, Atmosphere …
Curious if any of the people looking at biological changes in the ocean have had time to address changes in this population as a possible change in feedback.
Ray Ladbury wrote: “So, anybody know any good jokes. We could be here awhile.”
A skeleton walks into a bar and orders a beer and a mop …
Ike Solem says
By the way, hydrocarbon aerosol formation is highly dependent on combustion conditions – you can do a simple experiment to see this for yourself. Take a butane lighter and hold a glass a good distance above the flame, and slowly lower the glass until it is touching the top of the flame. At some point you will see a sudden deposition of soot, which otherwise does not form. This may be because the glass forms a condensation surface, or because it interferes with oxygen delivery. (That’s also why a poorly adjusted gas furnace can produce toxic levels of carbon monoxide and other pollutants).
Historically, this is what “clean combustion” has meant – adjusting combustion processes in order to minimize the emission of anything other than water and CO2. Modern internal combustion engines and IGCC-type coal turbines do a good job of this, with some drawbacks, like cost. However, if fossil CO2 itself is the problem, than “clean” combustion does you no good.
This is where photosynthetically produced biofuels come into play – but they will still produce black carbon aerosols during combustion if burned in older turbines or engines. Soot from wood and biofuels is less toxic than fossil fuel soot (biofuels lack sulfur, mercury, arsenic, selenium, etc.) but is still best avoided. As with fossil fuels, the bigger the molecule, the dirtier the combustion products. Wood smoke is more toxic than biodiesel exhaust, which is dirtier than ethanol exhaust, with biomethane and biohydrogen being the equivalents of natural gas, only cleaner (natural gas often occurs with highly toxic hydrogen sulfide).
Of course, nuclear provides heat without combustion, but suffers from the need for vast amounts of cold water to cool the reactor and transfer energy to the steam turbine that generates electricity.
Solar and wind provide clean electricity with no need for water for cooling, but are intermittent power sources and require storage technologies, batteries or fuel cells.
While each of these technologies has it’s disadvantages, it is easy to envisage an energy system that relies on a mixture of existing nuclear, solar, wind and advanced biofuels – with no fossil fuel use at all.
I am curious if you have any insights regarding a relationship between the GCR presence in the upper troposphere and barometric high pressure (anti-cyclonic) systems? I have reviewed the earlier RC posts and note that there seems to be a casual relationship between CRs and low altitude cloud (Marine layer) formation.
If I understand your position above, it appears you are relating that the increase of presence of CGRs could act as seed CCN, eventually… To restate my question, given your explanation is it possible that these “seed particles” could contribute to a falling air mass in the 250mb and above range that could spark the formation of a anti-cyclonic event.
Please understand, I am NOT relating this to the GW issue. I am more curious if this could be a possible explanation for the recent optical depth variations getting play in the “global dimming” observations.
Hank Roberts says
I’m starting to read Carslaw et al. “a nice overview of potential relations between cosmic rays, clouds and climate.” Trying to learn.
“dunno reformer” says ReCaptcha
Pekka Kostamo says
Dr. Verheggen, thank you for a very good article.
A major first effort of a propagandist is always to “set the right frame” for a discussion. Even today, in nearly all the “it-is-the-sun” based discussions the frame is still set by reference to the old and infamous Svensmark press release discussed by Gavin in “Taking Cosmic Rays for a spin”. Unfortunately so.
Another paper of relevance might be:
Cosmic rays, CCN and clouds – a reassessment using MODIS data
J. E. Kristjansson, C. W. Stjern, F. Stordal, A. M. Fjæraa, G. Myhre, and K. Jonasson.
They try to find immediate impacts of specific short term fluctuations found on the cosmic radiation records upon cloud observations, MODIS providing additional interesting parameters. There seems to be nothing, but maybe they did not allow enough time for the coagulation process to run its full course. They explored over a few days, you indicate a week or two.
Brian Dodge says
There’s probably a simple reason why this is a stupid question, but why wouldn’t increased production of positive and negative charged particles by GCRs cause cloud particles to coalesce and rain out, sorta like an ionic air filter? I realize that charged aerosols sticking to a wall, floor, or plates in a purifier is different from them sticking to each other and growing big enough for gravity to start having an influence, but it still seems like that would tend to occur. Wouldn’t neutral aerosols be attracted to charged particles because of surface charge redistribution, become charged, be attracted to oppositely charged particles and aerosols (neutral or oppositely charged), growing and coalescing more rapidly with higher rates of GCR charge particle production?
Timothy Chase says
Alan Millar wrote in 23:
There are climate models that didn’t include reflective aerosols?
Wouldn’t you agree that if a surface is absorbing fewer watts of radiation per square meter it will be cooler than an otherwise identical surface absorbing more watts of radiation per square meter? And wouldn’t you agree that putting reflective aerosols such as sulfates into the air will reduce the amount of light that reaches the surface of the earth? I mean, would you regard either of these two propositions as “ad hoc hypotheses” pulled out of “thin air” to save the “hypothesis” that all other things being equal, more carbon dioxide raises the temperature of the earth?
However, we don’t assume any of these things. We can measure the spectral properties of sulfates, nitrates and carbon dioxide, spectral properties which imply that sulfates and nitrates are reflective and therefore imply that they reduce the amount of radiation that reaches and therefore warms the surface. We can measure the absorption spectra of carbon dioxide, which implies that it does not impede visible light from reaching the surface, but that it does impede long-wave thermal radiation from making it to space while simultaneously resulting in backradiation which further warms the surface. Moreover, the spectral properties of carbon dioxide basically fall right out of the first principles of quantum mechanics.
Alan Millar wrote in 23:
Won’t be quite that localized since the half-life of tropospheric aerosols is typically 1-2 weeks. Aerosols can do a lot of moving around in that amount of time. Places that act as sources for aerosols will be downwind of those which don’t and visa versa. However, for the most part they tend to remain in the hemisphere that they originate in rather than being equally distributed in both.
As such, you might want to look at this:
Think about it: if the effects of carbon dioxide are weak but cummulative and the effects of aerosols are strong but ephemeral, which do you think is going to win out in the short-run? In the long-run?
But what if the sulfates are injected into the stratosphere — where they won’t be rained out until they drift into the troposphere a couple of years or so later?
Check this out:
Timothy Chase says
Hank Roberts wrote in 29:
Also along these lines, people might check out…
or for something non-technical:
Evidence Of ‘Rain-making’ Bacteria Discovered In Atmosphere And Snow
ScienceDaily (Feb. 29, 2008)
Hank Roberts wrote in 29:
The following would appear to be a step in that direction:
Christner, B.C., R. Cai, C.E. Morris, K.S. McCarter, C.M. Foreman, M.L. Skidmore, S.N. Montross, and D.C. Sands. 2008. Geographic, seasonal, and precipitation chemistry influence on the abundance and activity of biological ice nucleators in rain and snow. Proceedings of the National Academy of Sciences, 105:18854-18859.
… but if Dr. Verheggen knows more, I am sure a number of us would appreciate it.
John Mashey says
re: #14 Ike
Sorry, this is mostly OT (so skip it if you want aerosols), but I offer some some experience and pointers as context for Ike’s comment:
‘Is there a connection between the SLAC view of cosmic rays and climate, the DOE’s support for coal, and Stanford’s Exxon-funded Global Climate and Energy Program? Interesting question, isn’t it?”
Actually, not very interesting, and if there’s a connection, it’s not obvious, especially as I know some of the relevant people.
1) SLAC does particle physics, and their full discussion didn’t seem unreasonable. There might be a few there who don’t accept fossil-fuel-forced AGW (there’s one who writes letters to innocent local newspapers), but their general worldview can be assessed via: Searcyh SLAC website for global warming. If SLAC does much with coal, it’s not obvious. DOE is big.
2) Ex-Director of SLAC and Stanford professor is Burton Richter, whose views on both climate & energy were fairly clear in that. He also led the recent APS report on energy efficiency, and quite often shows up for the fine public Stanford Energy Seminar Series, Wed’s at 4:15PM, sponsored by the Woods Institute. Schedule for next few months is here. The seminars are sponsored by Chevron. Among the recent speakers was Michale Klare, whose most recent book: “Rising Powers: Shrinking Planet – The New Geopolitics of Energy” is highly recommended … but probably wouldn’t gladden any oil person very much.
3) Stanford GCEP has a 3-day symposium each Fall, free & open to public, although you have to sign up a month or two in advance. A very interesting audience comes out for these.
GCEP is sponsored by: ExxonMobil, General Electric, Schlumberger, and Toyota.
Last Fall’s talks are mostly posted here, and it was a nice event, with many poster sessions as well as the talks. As one can see from Sally Benson’s talk, 29% of their effort goes to carbon-based energy systems (10% CO2 storage, 7% CO2 capture, 3% advanced coal, 9% advanced combustion), 40% goes to renewables, 11% to hydrogen, 11% to electrochemical transformations. One of the most interesting talks was that of Caltech’s Nate Lewis.
One can look at the presentations to assess what people are doing. My opinion is that some fairly rational people think someone has to do some actual research to figure out if, when, where, and how expensive CCS is. If they thought it was ready to ship, they wouldn’t be interested.
4) Energy Efficiency is the focus of PEEC – Precourt Energy Efficiency Center, which got a big boost in January.
5) Many climate, energy, and efficiency folks are housed together in the recently-completed Y2E2 building, worth a visit.
(Note: I have no association with Stanford, although I’ve done a few lectures there. I just live nearby, so it is easy to attend the numerous good climate & energy events and talk to faculty.)
Bart Verheggen says
Alan Millar (23),
You seem to confuse uncertainty with knowing nothing.
You are referring to two different hypotheses (GHG and aerosol forcing), but a better description is that there are multiple climate forcings at work (not just CO2 and aerosols), and that only by taking them all into account to the best of our ability do we get a very decent match between models and observations. That, together with the paleorecord and current observations, counts for something.
The reflective nature of aerosols can readily be observed on a hazy day. It can be measured as well. The fact that aerosols are needed for clouds to form can also readily be shown. Without any aerosols the RH would have to rise to about 400% for water droplets to form.
Try this little experiment: take a PET bottle and wash it out with water. Close it. Compress it with both your hands and then let suddenly go (decompress). What do you see? (likely nothing).
Now light a match and let part of the smoke enter the PET bottle. Compress and decompress again. What do you see? (likely a thin, though short lived, cloud-in-a-bottle) Voila the evidence that more aerosols aid in cloud formation. Takes one minute.
James Allan says
Hi Bart, nice articles. The plot from Pacific 2001 in the first one brings back memories. ;-)
Interesting that you touch on the elusive phenomenon of marine boundary layer nucleation. Based on all the observations I know of, it’s not been measured in situ anywhere near the sea surface (except for coastal areas and in ship plumes), but then again, all the Aitken-mode non sea salt particles in the remote MBL have to be coming from somewhere. A lot of people have their pet theories on this one, but I was just wondering if you had any you were willing to stick your neck out over?
Barton Paul Levenson says
Alan Miller writes:
No, they aren’t. Where did you get that idea?
James Allan says
Sorry, that last question is maybe a little cryptic. To clarify, do you think it is just that we don’t have enough observations or do you think that there is a process at work that we haven’t properly characterised yet?
Martin Vermeer says
Alan Millar #23:
See Figure 9.5.
Ray Ladbury says
Alan Millar @23, Actually, Alan, you and I have something in common:
Neither of us has a clue what the hell YOU are talking about. Where on Earth (or off, for that matter) do you get your information.
The effects of aerosols are PART OF the models. Put in a source of aerosols (be it dirty fossil fuel production or Mt. Pinatubo) and you get cooling. Actually, this was known even before the GCMs had much skill. Even in the ’70s, the concern some scientists had over “global cooling” (you know, the one you guys try to attribute to ALL climate scientists) was driven by pollution from fossil fuels. It turns out that the reason things didn’t cool significantly was that CO2 sensitivity was higher than the level favored by scientists who expressed concern about cooling. Oops. Another own goal. Anybody keeping score anymore?
“Alan Millar (23),
You seem to confuse uncertainty with knowing nothing.”
Yup, that’s what they do.
No need to have an explanation, just tear down the one you don’t want.
The scientific analogue of “negative voting”.
“There’s probably a simple reason why this is a stupid question, but why wouldn’t increased production of positive and negative charged particles by GCRs cause cloud particles to coalesce and rain out, sorta like an ionic air filter?”
A counter to that effect is that such small water droplets have a large surface area. And if they are in a dry atmosphere (significantly less than 100% RH) then these droplets will evapourate quickly and you no longer have droplets.
There’s a reason why condensing trail instruments use high RH closed tubes for recording ion tracks.
PS it isn’t a stupid question, it’s only half a question.
You don’t consider what happens AFTER such creation.
If such creation were so simple, there would have been no problems in cloud seeding in the 70’s-date.
GCR seem to be a hot topic of late. I suppose there is not enough evidence to completely rule out a more significant role since we have not had the chance to research a deep solar minimum, until now,…. maybe ?
Hypothetically, if high GCR does play a more significant role in global temperature this does not necessarily detract from the positive effect of CO2 in causing warming. It simply adds another piece to the total climate equation. Not sure why we need to be too defensive on this ?
For those interested in GCR here is a link to Oulu in Greenland,
The count is now at ~6850 and still rising – if this is really important ?
Alan of Oz says
OT – Carbon capture. A lot of govt money has gone into CSS, $AU2.5 billion here in Oz alone. I think this is a small step in the right direction to a definitive answer in the near future.
IMHO virtually all governments have dropped the “it’s not us” claims and the coal fired countries are at least starting to go through the motions of asking; where’s the ROI from our CCS grants?
“GCR seem to be a hot topic of late. I suppose there is not enough evidence to completely rule out a more significant role since we have not had the chance to research a deep solar minimum, until now,…. maybe ?”
Depends on what you mean by “significant”.
The simulations of what we KNOW about CO2 and the feedbacks are sufficient to explain what is seen without GCRs having a significantly bigger role than they are currently given (they ARE given a role, note).
And you forget to say there’s not enough evidence to completely rule out a less significant role for GCR effects either.
Why is uncertainty a one-way street for some?