Posts Tagged ‘climate’

New definition of lukewarmer

June 8, 2011

This self-description of a lukewarmer (at Bishop Hill) gave me a good laugh:

Now I’m probably some sort of a lukewarmer – I don’t e.g. agree with Turning Tide that the fact that CO2 concentrations are low means ipso facto that it is irrelevant.

Like luketoxers who acknowledge the fact that arsenic in low concentrations doesn’t ipso facto mean that it’s irrelevant. It’s like saying I’m not a total doorknob.

Curious, I went back to read what Turning Tide had written and came across this gem:

What I found most telling is how certain facts about the atmosphere are very hard to track down for the layperson. For example, I’m pretty sure the average joe has no idea how little CO2 there is in the atmosphere, and how small a proportion of that little amount is contributed by human activities. It’s almost as though there’s a conspiracy of silence to keep such information out of easily accessible sources.

Can everyone who has a CO2 concentration widget on their blog please remove it now? We’ve got to keep it a secret that its concentration is a meagre 395 parts per million.


Venus battle resolved?

June 7, 2011

Jeff Id took issue with Chris Colose for bringing up the high surface temperature at Venus in his SkS post

CO2 is a strong greenhouse gas, and it is important in impeding how efficiently our planet loses radiative heat to space.  We don’t often think of CO2 as a “pollutant” on Venus, yet it still allows the planet to support temperatures well above the melting point of lead or tin.

Jeff replied at his blog:

Venus does have a more reflective atmosphere but it is also closer to the sun than the Earth.  For the thinking mind, it is difficult to ignore that the atmosphere is a ridiculous 90 times more dense. (…) In fact, if you just used Nitrogen alone at the same mass you would get a ton of heat just by the insulating properties of a gas.

On a subsequent post he reiterates his thought that

the reason for Venus surface temeprature being so high was the pressure and that any gas would create a huge warming effect 

However, during the discussion he seems to be backpedaling:

#15, Chris, (…)

My reply was that it was the pressure and amount of gas which caused the temperature more than the specific greenhouse effect of some particularly powerful gas. I pointed out that even N2 would cause a ton of warming with wording that clearly recognized there would be less warming and a paper was referenced where even the 96.5 percent N2 atmosphere had 80C of warming. I was also careful not to claim that all gasses would definitely cause a hot Venus and intentionally phrased even that as a question. In other words, you are making assumptions of a point I didn’t state.

To be fair, I admit that a pure nitrogen atmosphere had less warming than I would have (but did not) guess.

Is it just me, or does that indeed sound like he agrees that the majority of the >500 degrees greenhouse effect on Venus stems from the radiative properties of its atmosphere (~96% CO2) rather than from its density/pressure? The impression I got from his post was that the opposite though. Makes me wonder what the argument is really about. So I asked:


It seems that you agree that the high temperature on Venus is due primarily to a strong CO2 greenhouse effect (few hundred deg) and secondarily (?) to the high surface pressure (the ~80 deg number that was mentioned upthread).

If so, then I don’t understand the beef you have with Chris’ take, where he uses Venus as an example that shows that CO2 is a greenhouse gas.  

Jeff replied:


I object to its comparison to Earth as a scare tactic in general. That’s all.

Argument resolved. Both agree that the greenhouse properties of Venus’ atmosphere are primarily responsible for its high surface temperature, and they disagree as to whether or how this could be mentioned in a discussion about Earth’s climate.

Quick rundown on Venus’ climate:

Venus is closer to the sun than the Earth, but its higher reflectivity more than compensates for that. Without a greenhouse effect Venus would actually be colder than the Earth would be without a greenhouse effect. In reality Venus is about 500 degrees warmer than this so called black body temperature (the greenhouse effect on the Earth is about 33 degrees). This is primarily due to the inception of infrared radiation by its thick atmosphere of almost pure CO2. The high density also helps, but is of secondary importance.

More reading:

Realclimate on Venus

SoD’s Venusian Mysteries

Brian Angliss at S&R

IPCC troubles in context: Some good Dutch media coverage

September 3, 2010

One of Holland’s quality newspapers, the Volkskrant, had some excellent coverage of the IAC’s review of the IPCC process. Below is my translation of (part of) an editorial column (discussed in Dutch in an earlier post):

In a way it was inevitable that the UN climate panel IPCC got cornered earlier this year when some mistakes were discovered in its reports. The IPCC, as a volunteer organization with a small staff, could no longer cope with the societal polarization which was the consequence of the unwelcome message of global warming and climate change. Thus, professionalization is required.


The mistakes and glitches which were discovered in the IPCC’s 2007 report were the result of clumsiness and sloppiness. They did not undermine the knowledge that the climate is changing.

I would add that most IPCC mistakes were minor or even imaginary, and most were in working group 2 about (regional) effects of climate change; they did not concern the physics of climate and why it is changing. (See  e.g. my commentary on the 2035 – 2350 glacier mistake, which is the only serious mistake, even if it is in a relatively insignificant and hardly read portion of the whole report. The Dutch area-under-sea-level slip was mostly clumsy.)

In spite of this it caused a wave of distrust, which suggests that climate science and IPCC as its flag bearer had a problem with their public image.

With not a little help from large quarters of the media. And of course human psychology to rather not believe things that you don’t want to be true.

On the one hand climate scientists are expected to keep themselves to the facts only. At the same time their results and understanding are also arguments in the societal discussions about climate change. But as soon as they participate in this discussion accusations of bias come up.

A more professional IPCC should not only work on the internal weaknesses and make and present itself as scientifically solid as possible. It will also have to make clear that its work has political implications, but that that doesn’t mean that it’s engaged in doing politics.

The last portion (my bold) should be self-evident, but since in reality many people and media chose to paint it as the opposite, it is unfortunately necessary to point out the obvious.

What does population have to do with climate change?

August 23, 2010

Population may not be the driving force behind many of the global world problems, but it’s certainly important: Basically, it is a multiplication factor for the environmental impact of certain actions. E.g. better environmental performance of some products has occasionally been offset by its much greater use (cf. population density). Of course, if a real innovation comes along, the environmental impact could be cut more drastically (which also happens, but counting on it may be risky).


The 20-80 story puts population in perspective: 20% of the world population uses approximately 80% of the worlds’ resources (dependent on the resource of course). That alone means that focusing on population isn’t where the shoe pinches in many cases: It’s the (over-)consumption in the rich areas that causes the most strain on the world’s resources.


On the other hand, I’ve understood that the reason that native cultures had relatively little impact on their environment is to a large extent due to their small population density. Burning a small piece of forest to use the land for food production may not be a great problem for the ecosystem if it only occurs sporadically, thereby not causing more disruption than the ecosystem can handle. It only becomes a problem when the magnitude increases above sustainable levels, which is intricately linked to population. There are plenty of examples in nature where too large numbers of a certain species causes stress on the ecosystem.

The Kaya identity shows that population is a multiplication factor, just as consumption is:

CO2 emission = population * GDP/capita * energy/GDP * CO2 emission/energy.

It would require a systemic analysis to see which factors are most responsible for a given problem, but it’s pretty clear that population is a factor that influences the total pressure on the system. The 80-20 ratio described above shows that consumption patterns by the rich cause the most strain on the world’s resources. I’d wager that the difference in consumption patterns between different parts of the world is (a lot) larger than the spread in population density, which would make the former most important. Population is not a factor that is easily or quickly influenced, but for the long term, it should be seriously considered as an important factor (especially because it has so much inertia).

Pointing fingers solely to, or firmly away from population, both misses the mark imho. reality is not black and white.

Greenhouse gases

How many people the earth can sustain of course depends on the other factors in the various Kaya identities: If everyone were to have the consumption pattern of an average American, we would already have overshot the long term carrying capacity of the earth. If we all live a Buddhist lifestyle, we could probably do with a few more people. It’s a trade off, as always.

Don’t want to use (and pay for) sustainable energy (cf consumption pattern)? Then use less energy (cf population).

Don’t want to use less energy? Then use (and pay for) sustainable energy.

Don’t want to do either? Go find another planet.

This leads to a major moral dilemma: Developing nations also want to increase their material welfare, but them doing so by mimicking our current ways of production and consumption is a recipe for disaster. OTOH, we have no more moral right to the earth’s riches as they do. Something has to give, obviously.

See also this thought provoking article by Michael Tobis, where he takes on the other, even bigger taboo: economic growth. Bottom line:

A given economic growth rate can be sustainable only if the average impact per unit wealth declines at an equal or greater rate.

I.e. if the carbon and energy intensities decrease at least as fast as the GDP increases.

Attempting to reach equitable economic prosperity and allowing for normally projected increases in GPD and population, Tobis estimates that the impact per unit of wealth has to decrease roughly 50 fold by 2050.

(Figures from Newman. Post based on a comment of mine over at Kloor’s blog)

Randy Olson on lemmings and leaders

August 20, 2010

Great article by Randy Olson at the Benshi, contemplating two polarized options of dealing with the climate crisis: like lemmings or like leaders.

Lemmings would tend to wait for the problem to become so massive that there’s just no other option than to deal with it, as in ‘we need a catastrophy before we start taking this problem seriously’.


leadership is what ought to be expected of a species of primates whose birth canals have had to widen over the ages to make space for enlarged crania.

He also discusses the following important point, based on the following suggestion he received from a friend:

“Accept arguments on the basis of evidence alone (not on the basis of who presents them).”

to which he counters:

That sounds great and admirable, at least in principle. But it’s not realistic in the complicated world of science-based issues. (…)

This is why we have leaders. It’s called civilization. At some point we put our trust in those with that stuff called “knowledge.” Like the IPCC. It’s not perfect, but it’s our best shot at avoiding the lemmings scenario.

For the complicated world of science-based issues, the lay person needs shortcuts to evaluate the trustworthiness of the information. One of my older posts that I like most deals with exactly that question. For health issues, it’s not much different.

And to plug another, unrelated but also very good article, Stephan Lewandowsky wrote a guest post over at Skeptical Science on short term uncertainty in the weather versus long term certainty in the climate, with the price winning quote:

There is uncertainty [about climate change], but only in the way that there is uncertainty about what happens when you drive into a brick wall at 80 km/h. You might just get away with a few bruises and a concussion, but it is far more likely that you would break a leg or worse.

No one in their right mind would drive into a brick wall because the outcome is “uncertain.”

Guest post at Realclimate on aerosol nucleation and climate

April 24, 2009

Guess it’s a little late notice, but I have a guest post at RealClimate on the potential effects of aerosol nucleation and cosmic rays on climate. For the whole article please see RealClimate. The bottom line is as follows.


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.

Aerosols, clouds and climate

April 16, 2009


Clouds can cool or warm the underlying surface. They reflect some of the incoming shortwave solar radiation back to space (cooling). They also absorb infrared radiation and re-radiate it to all directions, with a wavelength (and thus energy) that depends on cloud temperature (and thus height). The latter is a quasi-greenhouse effect (warming).


The colder (=higher) the cloud, the less energy will be re-radiated to space, so the more the atmosphere will warm. (The same happens with greenhouse gases: the higher re-radiation into space takes place, the less energy is lost, and the more the atmosphere will warm. In that sense, the sky is the limit in terms of a warming effect of CO2: no matter if the absorption bands at the surface would be saturated, it would just move up the re-radiation to a higher altitude, thereby still adding to the warming effect.)

At night, there’s no solar radiation to reflect, and so clouds mainly warm the surface. However, the net effect of clouds is a cooling.


The basic response of liquid water clouds to an increased CCN population is expected to be a change in the droplet size spectrum: Assuming the liquid water content remains relatively unchanged, more cloud droplets will form, having a smaller average size. Absorption depends on particle volume, whereas reflection depends on its geometric cross-section, and thus the ratio of reflection over absorption of the cloud increases as the droplet size decreases. Dependent on the altitude of the cloud droplets, and the albedo of the underlying surface, this will usually result in cooling. A smaller average droplet size may increase cloud lifetime, via the suppression of rain. Cloud cover could be susceptible to CCN concentration, especially in remote areas. In reality, different feedback mechanisms involving micro-physics and radiative transfer make the picture more complicated. For example, the liquid water content of a cloud is highly variable and not much is known about the response of liquid water content to increasing CCN concentrations.


The effects mentioned here concern only “warm” clouds; much less is known about the response of ice clouds. If through human activities the concentration of ice nuclei has also decreased (e.g. black carbon), there could be a “glaciation indirect effect”: more ice nuclei cause a cloud to rain out quicker, and may thus lead to a decrease in cloud cover (i.e. opposite to the “warm” indirect effect). This is still very hypothetical, however.


From local measurements of ship tracks, relations were found between particle emissions, cloud droplet diameter and cloud albedo. Still, more simultaneous measurements of aerosol particles, cloud droplets and radiative properties are necessary to gain a more accurate understanding of climate change. There are strong indications that besides inorganic salts, some organic compounds may also contribute to the CCN activity of an aerosol. Ultimately though, size may matter more than chemistry for the cloud nucleating ability of aerosols.

The atmospheric aerosol

April 13, 2009


This serves as an introduction to atmospheric aerosols to accompany my guest post on RealClimate. I’ll be discussing more about aerosols in the near future, including their potential role in GeoEngineering.



Atmospheric aerosol refers to the liquid or solid particles suspended in the air. They can be emitted directly into the atmosphere (primary aerosol), or they can be formed in the atmosphere by gas-to-particle conversion (secondary aerosol). The oxidation of precursors, such as SO2, NO2, and suitable organic compounds, can produce compounds with very low vapor pressures. These can condense to form a new particle, often in combination with other species, such as water vapor and NH3, a process called homogeneous nucleation. They can also condense on existing particles and contribute to them growing in size, referred to as condensation. Furthermore, aerosol particles can undergo evaporation, deposition, and coagulation, whereby two particles collide to form one larger particle. All these processes influence the evolution of the aerosol population in time.



Atmospheric aerosol particles span several orders of magnitude in diameter, from a few nanometer to hundreds of micrometer. Cloud droplets and raindrops can grow even larger, but are usually treated separately. Though not all particles are spherical, they are usually characterized according to their equivalent spherical diameter. Most of the properties, and thus effects, of particles depend on their size.



The tropospheric number concentration of aerosol particles ranges from several tens or hundreds per cubic centimeter of air in remote locations, to more than hundred thousand a million per cubic centimeter in polluted environments or after a strong nucleation event. The number concentration as a function of particle size is described by a size distribution. An important feature of atmospheric aerosol size distributions is their multimodal character: commonly found are the aitken mode, the accumulation mode, and the coarse mode. The nucleation mode consists of freshly nucleated particles and usually occupies diameters below a few tens of nanometers. The accumulation mode can vary in size between 50 nanometer and 1 micrometer, and its name comes from the fact that particles tend to accumulate in this size range, because they bear the longest lifetime (~2 weeks): smaller particles are efficiently removed by deposition and coagulation, and larger particles are efficiently removed by gravitational settling. The coarse mode usually refers to particles larger than 1 micrometer diameter. Sometimes an Aitken mode is defined as the mode that could exist between the nucleation and accumulation mode.

The number concentration of the atmospheric aerosol is usually dominated by sub-micrometer particles, while the total particle surface area and volume (and thus mass) are more influenced by larger particles. The exact shape of the size distribution depends on the environment, as it reflects the sources, sinks, and transformations of the particles.



Atmospheric particles have both natural and anthropogenic sources.

Examples of natural (primary) particle emissions are the shattering of sea-spray into tiny droplets, that evaporate before gravitating back towards the water surface, particles caused by forest fires, soil dust, pollens, etc. Examples of natural emissions of precursors to (secondary) aerosol are SO2 and H2S from volcanoes, dimethylsulfide (DMS) from phytoplankton, volatile organic compounds such as monoterpenes from vegetation, etc.

Examples of anthropogenic (primary) particle sources are vehicular emissions, industrial emissions, and some natural sources that are significantly enhanced by human activities, such as biomass burning and soil dust (due to e.g. erosion). Anthropogenic precursors to (secondary) aerosol are emitted by industry, burning of fossil fuels, usage of solvents, etc. Primary emissions contribute relatively more to the aerosol volume (because they’re often large), while gas to particle conversion (secondary aerosol) contributes relatively more to the aerosol number.


Cloud formation

Aerosol particles are necessary for clouds to form: Dependent on their size, composition and hygroscopic properties, they can act as cloud condensation nuclei (CCN) on which the available water vapor condenses, when it reaches a certain critical super-saturation of a few tenths of a percent. This process is called (cloud droplet) activation. Without these substrates to condense on, the relative humidity would have to exceed several hundred percent in order for the water vapor to overcome the Kelvin effect and homogeneously nucleate into droplets.

Similarly, some aerosol particles act as ice nuclei on which water can freeze into an ice crystal. Aerosol particles also provide a surface for specific heterogeneous reactions to take place, and thus affect the chemistry of the atmosphere.


Health effects

Atmospheric aerosols have potentially far reaching effects on health, ecosystems, and climate. Aerosol particles are a major component of smog, and act to reduce visibility. Their health effects are mainly due to their adverse effects on the respiratory function, and some also act as irritants for the eyes. Small particles can enter deep into the lungs, reaching the alveoli, where the transfer of O2 and CO2 takes place. H2SO4 is often a major component of these small particles, and dependent on their history other toxic compounds, such as heavy metals and PAH’s, could also have partitioned into the particle phase. Due to their low volatility, these species would otherwise not have reached that deep into the lungs. Atmospheric particles have been found to play a major role in excess mortality in epidemiological studies in several cities. Through their acid composition, aerosol particles also contribute to acidification of ecosystems.


Climate effects

Atmospheric particles contribute to climate change directly by scattering or, in the case of black carbon, absorbing sunlight, and indirectly by changing the radiative properties and lifetime of clouds. Both direct and indirect radiative forcing are influenced by particle size, composition and relative humidity. These processes are responsible for the largest amount of uncertainty in assessing climate change. The upper end of the estimated (direct and indirect) negative forcing of atmospheric aerosols could -at least on a global and annual average- balance the positive forcing of CO2. This does not necessarily mean that on a regional scale the opposing forcing mechanisms will balance each other. Aerosols are not homogeneously mixed throughout the globe, whereas the atmospheric lifetime of most greenhouse gases is much larger, so they will get distributed equally over the globe, despite large spatial differences in emissions.



The short lifetime (days to weeks) of aerosols is an important reason for the uncertainty in their role in climate change. It causes their concentration to be highly variable in time and space, and it’s hard to even know what the global concentration is, let alone what it was in the pre-industrial era. Add to that their variability in size and chemical composition, and the poorly understood role of clouds, and it’s clear that the uncertainty in aerosol radiative forcing will remain a steady feature of climate science for some time to come.


Other introductory explanations about aerosols are here, here, and here (German) and good presentation slides here.


%d bloggers like this: