Proposal

A guaranteed minimum electricity price (indexed and time-averaged over each 5 year period, for the design life of each project) for long-term investors in carbon free (<50gCO2/kWh) electricity generation capacity.

(more…)

The complete WG1 IPCC 4th Assessment report (AR4) is now available online. It's missing the index and some supplemental data, but all should be available by May 7.

Over the next few weeks we'll try and go through the report chapter by chapter, but since this is likely to the key reference for a number of years, we can take a little time to do it properly. Happy reading!

Eric Steig

When I give talks about climate change, the question that comes up most frequently is this: “Doesn’t the relationship between CO₂ and temperature in the ice core record show that temperature drives CO₂, not the other way round?"

On the face of it, it sounds like a reasonable question. It is no surprise that it comes up because it is one of the most popular claims made by the global warming deniers. It got a particularly high profile airing a couple of weeks ago, when congressman Joe Barton brought it up to try to discredit Al Gore’s congressional testimony. Barton said:

In your movie, you display a timeline of temperature and compared to CO₂ levels over a 600,000-year period as reconstructed from ice core samples. You indicate that this is conclusive proof of the link of increased CO₂ emissions and global warming. A closer examination of these facts reveals something entirely different. I have an article from Science magazine which I will put into the record at the appropriate time that explains that historically, a rise in CO₂ concentrations did not precede a rise in temperatures, but actually lagged temperature by 200 to 1,000 years. CO₂ levels went up after the temperature rose. The temperature appears to drive CO₂, not vice versa. On this point, Mr. Vice President, you’re not just off a little. You’re totally wrong.

Of course, those who've been paying attention will recognize that Gore is not wrong at all. This subject has been very well addressed in numerous places. Indeed, guest contributor Jeff Severinghaus addressed this in one of our very first RealClimate posts, way back in 2004. Still, the question does keep coming up, and Jeff recently received a letter asking about this. His exchange with the letter writer is reproduced in full at the end of this post. Below is my own take on the subject.

First of all, saying "historically" is misleading, because Barton is actually talking about CO₂ changes on very long (glacial-interglacial) timescales. On historical timescales, CO₂ has definitely led, not lagged, temperature. But in any case, it doesn't really matter for the problem at hand (global warming). We know why CO₂ is increasing now, and the direct radiative effects of CO₂ on climate have been known for more than 100 years. In the absence of human intervention CO₂ does rise and fall over time, due to exchanges of carbon among the biosphere, atmosphere, and ocean and, on the very longest timescales, the lithosphere (i.e. rocks, oil reservoirs, coal, carbonate rocks). The rates of those exchanges are now being completely overwhelmed by the rate at which we are extracting carbon from the latter set of reservoirs and converting it to atmospheric CO₂. No discovery made with ice cores is going to change those basic facts.

Second, the idea that there might be a lag of CO₂ concentrations behind temperature change (during glacial-interglacial climate changes) is hardly new to the climate science community. Indeed, Claude Lorius, Jim Hansen and others essentially predicted this finding fully 17 years ago, in a landmark paper that addressed the cause of temperature change observed in Antarctic ice core records, well before the data showed that CO₂ might lag temperature. In that paper (Lorius et al., 1990), they say that:

changes in the CO₂ and CH₄ content have played a significant part in the glacial-interglacial climate changes by amplifying, together with the growth and decay of the Northern Hemisphere ice sheets, the relatively weak orbital forcing

What is being talked about here is influence of the seasonal radiative forcing change from the earth's wobble around the sun (the well established Milankovitch theory of ice ages), combined with the positive feedback of ice sheet albedo (less ice = less reflection of sunlight = warmer temperatures) and greenhouse gas concentrations (higher temperatures lead to more CO₂ leads to warmer temperatures). Thus, both CO2 and ice volume should lag temperature somewhat, depending on the characteristic response times of these different components of the climate system. Ice volume should lag temperature by about 10,000 years, due to the relatively long time period required to grow or shrink ice sheets. CO₂ might well be expected to lag temperature by about 1000 years, which is the timescale we expect from changes in ocean circulation and the strength of the "carbon pump" (i.e. marine biological photosynthesis) that transfers carbon from the atmosphere to the deep ocean.

Several recent papers have indeed established that there is lag of CO₂ behind temperature. We don't really know the magnitude of that lag as well as Barton implies we do, because it is very challenging to put CO₂ records from ice cores on the same timescale as temperature records from those same ice cores, due to the time delay in trapping the atmosphere as the snow is compressed into ice (the ice at any time will always be younger older than the gas bubbles it encloses, and the age difference is inherently uncertain). Still, the best published calculations do show values similar to those quoted by Barton (presumably, taken from this paper by Monnin et al. (2001), or this one by Caillon et al. (2003)). But the calculations can only be done well when the temperature change is large, notably at glacial terminations (the gradual change from cold glacial climate to warm interglacial climate). Importantly, it takes more than 5000 years for this change to occur, of which the lag is only a small fraction (indeed, one recently submitted paper I'm aware of suggests that the lag is even less than 200 years). So it is not as if the temperature increase has already ended when CO₂ starts to rise. Rather, they go very much hand in hand, with the temperature continuing to rise as the the CO₂ goes up. In other words, CO₂ acts as an amplifier, just as Lorius, Hansen and colleagues suggested.

Now, it there is a minor criticism one might level at Gore for his treatment of this subject in the film (as we previously pointed out in our review). As it turns out though, correcting this would actually further strengthen Gore's case, rather than weakening it. Here's why:

The record of temperature shown in the ice core is not a global record. It is a record of local Antarctic temperature change. The rest of the globe does indeed parallel the polar changes closely, but the global mean temperature changes are smaller. While we don't know precisely why the CO₂ changes occur on long timescales, (the mechanisms are well understood; the details are not), we do know that explaining the magnitude of global temperature change requires including CO₂. This is a critical point. We cannot explain the temperature observations without CO₂. But CO₂ does not explain all of the change, and the relationship between temperature and CO₂ is therefore by no means linear. That is, a given amount of CO₂ increase as measured in the ice cores need not necessarily correspond with a certain amount of temperature increase. Gore shows the strong parallel relationship between the temperature and CO₂ data from the ice cores, and then illustrates where the CO₂ is now (384 ppm), leaving the viewer's eye to extrapolate the temperature curve upwards in parallel with the rising CO₂. Gore doesn't actually make the mistake of drawing the temperature curve, but the implication is obvious: temperatures are going to go up a lot. But as illustrated in the figure below, simply extrapolating this correlation forward in time puts the Antarctic temperature in the near future somewhere upwards of 10 degrees Celsius warmer than present -- rather at the extreme end of the vast majority of projections (as we have discussed here).

Global average temperature is lower during glacial periods for two primary reasons:
1) there was only about 190 ppm CO₂ in the atmosphere, and other major greenhouse gases (CH4 and N2O) were also lower
2) the earth surface was more reflective, due to the presence of lots of ice and snow on land, and lots more sea ice than today (that is, the albedo was higher).
As very nicely discussed by Jim Hansen in his recent Scientific American article, the second of these two influences is the larger, accounting for about 2/3 of the total radiative forcing. CO₂ and other greenhouse gases account for the other 1/3. Again, this was all pretty well known in 1990, at the time of the Lorius et al. paper cited above.

What Gore should have done is extrapolated the temperature curve according this the appropriate scaling -- with CO₂ accounting for about 1/3 of the total change -- instead of letting the audience do it by eye. Had he done so, he would have drawn a line that went up only 1/3 of the distance implied by the simple correlation with CO₂ shown by the ice core record. This would have left the impression that equilibrium warming of Antarctica due to doubled CO₂ concentrations should be about 3 °C, in very good agreement with what is predicted by the state-of-the-art climate models. (It is to be noted that the same models predict a significant delay until equilibrium is reached, due to the large heat capacity of the Southern ocean. This is in very good agreement with the data, which show very modest warming over Antarctica in the last 100 years). Then, if you scale the Antarctic temperature change to a global temperature change, then the global climate sensitivity to a doubling of CO₂ becomes 2-3 degrees C, perfectly in line with the climate sensitivity given by IPCC (and known from Arrhenius's calculations more than 100 years ago).

In summary, the ice core data in no way contradict our understanding of the relationship between CO₂ and temperature, and there is nothing fundamentally wrong with what Gore says in the film. Indeed, Gore could have used the ice core data to make an additional and stronger point, which is that these data provide a nice independent test of climate sensitivity, which gives a result in excellent agreement with results from models.

A final point. In Barton's criticism of Gore he also points out that CO₂ has sometimes been much higher than it is at present. That is true. CO₂ may have reached levels of 1000 parts per million (ppm) -- perhaps much higher -- at times in the distant geological past (e.g. the Eocene, about 55 million years ago). What Barton doesn't bother to mention is that the earth was much much warmer at such times. In any case, more relevant is that CO₂ has not gone above about 290 ppm any time in the last 650,000 years (at least), until the most recent increase, which is unequivocally due to human activities.

Dear Jeff,

Jeff

Michael Mann and Gavin Schmidt

A recent paper by Vecchi and Soden (preprint) published in the journal Geophysical Research Letters has been widely touted in the news (and some egregiously bad editorials), and the blogosphere as suggesting that increased vertical wind shear associated with tropical circulation changes may offset any tendencies for increased hurricane activity in the tropical Atlantic due to warming oceans. Some have even gone so far as to state that this study proves that recent trends in hurricane activity are part of a natural cycle. Most of this is just 'spin' (pun intended), but as usual, the real story is a little more nuanced.

We have commented on the connections between hurricanes and climate change frequently in the past (see e.g. here, here, here, and here). The bottom line conclusion has consistently remained that, while our knowledge of likely future changes in hurricanes or tropical cyclones (TCs) remains an uncertain area of science, the observed relationship between increased intensity of TCs and rising ocean temperatures appears to be robust (Figure 1). There is nothing in this latest article that changes that.

Figure 1. Measure of total power dissipated annually by tropical cyclones in the North Atlantic (the power dissipation index "PDI") compared to Aug-Oct tropical North Atlantic SST (from Emanuel, 2005; data)

The Vecchi and Soden (V+S) study suggests that increased 'vertical wind shear' in the tropical Atlantic might overcome this effect. Wind shear is related to the rate at which different layers in the atmosphere move - zero shear means that the layers all move together, large shear means that the upper layers are moving very differently to those below - and is inimical to hurricane formation and intensification. The well-known impact of El Niño on reducing Atlantic hurricane activity is in fact due to increased shear from the associated atmospheric circulation changes. The V+S results come from analysing the results of 18 different model simulations that were done for the IPCC AR4 and which now provide a superlative database for assessing what models do and do not project. It's important to be clear that these models do not resolve hurricane processes and that the analysis is related to the large scale 'background' environment in which hurricanes form. Nonetheless the idea of looking at these simulations to see what happens to that large scale environment, as V+S have done, is certainly interesting and worthwhile.

V+S find that the IPCC AR4 models produce an decrease in shear near the equator and an increase in the subtropics. Over the 'Main Development Region' for Atlantic hurricanes, the results are mixed and, to our eyes at least (see Figure 2), don't provide a compelling argument for hurricane activity reductions. However, the conclusions rest heavily on something that is not robust at present; the prediction of mean changes in the Walker circulation. As we have discussed in some detail, this latter issue rests upon considerations that take us to the heart of where the models are currently at their weakest--getting marine stratocumulus clouds right, producing a realistic intertropical convergence zone in the tropical Pacific, producing realistic Kelvin wave behavior in the tropical Pacific ocean--things that are all critical for an accurate representation of the Bjerknes feedbacks which are, in turn, so central to the mean state and variability of the Walker circulation (and El Niño). It is conceivable that the various simulations in the AR4 ensemble analyzed by V+S are at the same time mostly in agreement, and yet wrong, in what they predict for future Walker circulation changes. The prediction of increased wind shear in the tropical Atlantic is no better than the underlying predictions in the models of Walker circulation changes.

Figure 2. Average of 18 models changes in Genesis Potential Index (GPI) of hurricanes for 2081-2100 (IPCC A1B scenario). GPI includes the effects of heating and wind shear. (Update: figure updated to fig 4d from the paper.)

Furthermore, the fact is (as shown in Figure 1) that hurricane intensity has increased in recent decades as SST has risen (at least in the North Atlantic for which trends are most reliable) and this prediction is based on fairly fundamental and robust thermodynamic arguments explored by Emanuel and others for decades now. Emanuel (2005) makes a compelling case that the warming ocean temperatures (and associated changes in atmospheric temperature and humidity profiles) are behind the increased TC intensity in the Atlantic. Independent analyses, such as those described in the Santer et al PNAS article, show that this warming is inconsistent with natural variability, i.e. it is likely only explainable in terms of anthropogenic forcing. That would seem to close the loop on the argument that anthropogenic forcing is likely behind a substantial component of the observed increased intensity of Atlantic TCs. So the observational evidence thus far is not in favour of increased shear preventing this increase in intensity.

This view is echoed by Kerry Emanuel in comments on the paper in the Washington Post, where he suggests that the impact of wind shear changes relative to warming SSTs in the real world, as diagnosed from trends observed thus far, may be overstated by the V+S study:

Emanuel, who was not involved in this research, said he published a study last year that calculated that increasing the potential intensity of a storm via warming by 10 percent increases hurricane power by 65 percent, whereas increasing shear by 10 percent decreases hurricane power by only 12 percent.

In the same WaPo article, Chris Landsea discusses these projections into the future as if they had relevance to the attribution of past change. While this mistake is often made, it is nonetheless incorrect. Attribution can only be done using simulations and observation of the period in question.

Finally, a cautionary note seems warranted. Suppose that the V+S findings are in fact correct, and that increased wind shear will play a substantial role in future changes in TC behavior. This could be a mixed blessing. Wind shear in the tropical Atlantic will remain highly variable from year to year, changing at the whim of individual El Niño and La Niña events which influence the Walker Circulation. Temperature trends, on the other hand, are far more steady over time, and every simulation examined by the Vecchi and Soden predicts substantial warming in the main development region for TCs in the tropical Atlantic in the decades ahead. While increases in wind shear could offset the impact of tropical temperatures in some -- maybe even the majority -- of storm seasons, one might worry about what happens during those seasons where there is anomalously low shear (e.g., a very strong La Niña event). The warm ocean will still be sitting there, waiting to produce tropical cyclones and Hurricanes--and the prospects for destructive Hurricane activity during those seasons could be especially grim. In short, the V+S results could presage a future where there is increased interannual variability in TC behavior, and where the worst Hurricane seasons are considerably more destructive than today.

The findings of V+S represent an important contribution to the ongoing scientific discourse on the issue of climate change impacts on tropical cyclones, and the study should spur additional work looking at the complicated issues involved in greater detail. It remains the case that the modeling of Hurricane-climate change interactions is still at a relatively primitive stage and this study is very unlikely to be the last word. We will of course follow the future developments closely.

By Tim Joslin
Full Article (pdf)

The threat of global warming has led governments around the world to encourage the use of biofuel, in particular in the transport sector, in the hope of displacing fossil fuel. The UK, following an EU Biofuels Directive, is introducing a Road Transport Fuel Obligation (RTFO), requiring fuel providers to ensure that 5% of their total road transport fuel sales “is made up of fuels from renewable sources” by 2010.

It is already well-known, through the efforts of, in particular, George Monbiot, that a large-scale diversion of agricultural land to the production of biofuel will set up competition between food and fuel, between people and cars. Vast tracts of rainforest are already being cleared to create more land on which to grow biofuel crops, such as oil palm. Governments may argue that they can manage these problems, whilst continuing to promote biofuel use. This is doubtful.

But there are even more fundamental arguments against biofuels. This paper shows that the use of biofuel to supplement fossil fuel for vehicle transport is not only disastrous in practice, it is also flawed even on its own terms, in two distinct ways:

1. plant-growth on land is one of the main ways in which CO2 is removed from the atmosphere. Land is therefore a resource in the fight against global-warming. Even under optimistic assumptions, growing biofuel crops will not reduce atmospheric levels of CO2 over any timescale of up to more than a century, compared to preventing deforestation or even simply leaving already cleared land alone and allowing natural plant growth to capture carbon.
2. we know that within a few decades we must dramatically reduce our reliance on fossil-fuels, especially in the transport sector, where capturing and sequestering carbon emissions would be very expensive. In terms of achieving this objective, the use of biofuel is counter-productive. Instead of encouraging investment in energy supplies that are renewable for the long-term, measures such as the RTFO incentivise businesses and individuals to make further investments in technology for burning fossil fuels. Government should instead encourage a technological path from hybrid cars, through plug-in hybrids, to electric cars. Instead of continuing to burn carbon, our future transport energy needs can be met by the generation of electricity using true renewable and/or nuclear technologies.

Biofuels are not the answer.

Full Article (pdf)

A lot has been made of a paper (Lyman et al, 2006) that appeared last year that claimed that the oceans had, contrary to expectation, cooled over the period 2003-2005. At the time, we (correctly) pointed out that this result was going to be hard to reconcile with continued increases in sea level rise (driven in large part by thermal expansion effects), and that there may still be issues with way that the new ARGO floats were being incorporated into the ocean measurement network. Now it seems as if there is a problem in the data and in the latest analysis, the cooling has disappeared.

Ocean heat content changes are potentially a great way to evaluate climate model results that suggest that the planet is currently significantly out of equilibrium (i.e. it is absorbing more energy than it is emitting). However, the ocean is a very big place and the historical measurement networks are plagued with sampling issues in space and time. Large scale, long term compilations globally (such as by Levitus et al, 2001; Willis et al, 2004) and regionally (i.e. North Atlantic) have indicated that the oceans have warmed in recent decades at pretty much the rate the models expected.

Since 2000, though, ARGO - which is a network of floats that move up and down in the ocean and follow the currents - has offered the potential to dramatically increase the sampling density in the ocean and provide, pretty much for the first time, continuous, well spaced data from the least visited, but important parts of the world (such as the Southern Oceans). Data on ocean heat content from these floats had been therefore eagerly anticipated.

Initial ARGO measurements were incorporated into the Willis et al, 2004 analysis, but as the ARGO data started to dominate the data sources from around 2003, Lyman et al reported that the ocean seemed to be cooling. These were only short term changes, and while few would confuse one or two anomalous years with a long term trend, they were a little surprising, even if they didn't change the long term picture very much.

The news this week though is that all of that 'cooling' was actually due to combination of a faulty pressure reading on a subset of the floats and a switch between differently-biased observing systems (Update: slight change in wording to better reflect the paper). The pressure error meant that the temperatures were being associated with a point higher in the ocean column than they should have been, and this (given that the ocean cools with depth) introduced a spurious cooling trend when compared to earlier data. This error may be fixable in some cases, but for the time being the suspect data has simply been removed from the analysis. The new results don't show any cooling at all.

Are we done then? Unfortunately no. Because of the paucity of measurements, assessments of ocean heat content need to use a wide variety of sensors, each with their own quirks and problems. Combined with switches in data sources over the years, there is a significant potential for non-climatic trends to creep in. In particular, the eXpendable BathyThermographs (XBTs - sensors that are essentially just thrown off the side of the ship) have a known problem in that they didn't fall as quickly as they were originally assumed to. This gives a warm bias (see this summary from Ingleby and Palmer or the paper by Gouretski and Koltermann) , particularly in data from the 1970s before corrections were fully implemented. We are still going to have to wait for the 'definitive' ocean heat content numbers, however, it is important to note that all analyses give long term increases in ocean heat content - particularly in the 1990s - whether they include the good ARGO data or exclude the XBTs or not).

There are a number of wider lessons here:

• New papers need to stand the test of time before they are uncritically accepted.
• The ARGO float data are available in near real-time, and while that is very useful, any such data stream is always preliminary.
• The actual problem with these data was completely unknowable when Lyman et al wrote their paper. This is in fact very common given the number of steps required to create global data sets. Whether it's an adjustment of the orbit of a satellite, a mis-calibration of a sensor, an unrecorded shift in station location, a corruption of the data logger or a human error, these problems often only get fixed after a lot of work.
• Anomalous results are often the driver of fundamental shifts in scientific thinking. However, most anomalous results end up being resolved much more straightforwardly (as in the case, or the MSU satellite issue a couple of years back).

Scientists working in a field build up a certain intuition about how things 'work'. This intuition can come from a gut instinct, deep theoretical understanding, robust model results, long experience with observations etc. New results that fall outside of that framework often have a tough time getting accepted, but if they are solid and get subsequent support they will generally be incorporated. But that intuition is also very good at detecting results that just don't fit. When that happens, scientists spend a lot of time thinking about what might be wrong - with the data, the analysis, the model or the interpretation. It generally pays to withhold judgment until that process is finished.

Gavin Schmidt and Michael Mann

As part of a much larger discussion on Learning to live with Global Warming in Newsweek recently, the editors gave some space for Richard Lindzen to give his standard 'it's no big deal' opinion. While we disagree, we have no beef with serious discussions of the costs and benefits of various courses of action and on the need for adaption to the climate change that is already locked in.

However, Lindzen's piece is not a serious discussion.

Instead, it is a series of strawman arguments, red-herrings and out and out errors.

Lindzen claims that because we don't know what the ideal temperature of the planet should be, we shouldn't be concerned about global warming. But concern about human-driven climate change is not because this is the most perfect of possible worlds - it is because, whatever it's imperfections, it is the world that society is imperfectly adapted to. Lindzen is well aware that predictions of weather are different from climate predictions (the statistics of weather), yet cheerfully uses popular conflation of the two issues to confuse his readers.

Lindzen claims that the known amount of 'forcing' on the system proves that CO₂ will only have a small effect, yet makes plain in the subsequent paragraph that the total forcing (and hence what the planet should be reacting to) is quite uncertain (particularly before the satellite era). If the total forcing is uncertain, how can he say that he knows that the sensitivity is small? This issue has been dealt with much more seriously than Lindzen alludes to (as he well knows) and it's clear that this calculation is simply too uncertain to constrain sensitivity on it's own.

Among the more egregious of Lindzen's assertions is this one:

Ten years ago climate modelers also couldn't account for the warming that occurred from about 1050 to 1300. They tried to expunge the medieval warm period from the observational record—an effort that is now generally discredited.

It's remarkable that Lindzen is able to pack so many errors into two short sentences. First of all, doubts about the global scale of warmth associated with the "Medieval Climate Anomaly" date back well over a decade and certainly precede any known attempts to use climate models to simulate Medieval temperatures [e.g. Hughes and Diaz (1994), Was there a ‘medieval warm period’, and if so, where and when?; there are even earlier conference proceedings that were published coming to similar conclusions]. To the best of our knowledge, the first published attempt to use a climate model and estimated forcing histories to simulate the climate of the past millennium was described less than 7 years ago in this Science article by Tom Crowley, not 10 years ago-- (a 43% error ). Crowley's original study and the other similar studies published since, established that the model simulations are in fact in close agreement with the reconstructions, all of which indicate that at the scale of the Northern Hemisphere, peak Medieval warmth was perhaps comparable to early/mid 20th century warmth, but that it fell well short of the warmth of the most recent decades. Not only has the most recent IPCC report confirmed this assessment, it has in fact extended it further back, concluding that the large-scale warmth of recent decades is likely anomalous in at least the past 1300 years. So we're puzzled as to precisely what Lindzen would like to have us believe was "expunged" or "discredited", and by whom?

Finally, we find it curious that Lindzen chose to include this very lawyerly disclaimer at the end of the piece:

[Lindzen's] research has always been funded exclusively by the U.S. government. He receives no funding from any energy companies.

Richard, one thinks thou dost protest too much! A casual reader would be led to infer that Lindzen has received no industry money for his services. But that would be wrong. He has in fact received a pretty penny from industry. But this isn't for research. Rather it is for his faithful advocacy of a fossil fuel industry-friendly point of view. So Lindzen's claim is true, on a technicality. But while the reader is led to believe that there is no conflict of interest at work behind Lindzen's writings, just the opposite is the case.

It should hardly be surprising to learn that Lindzen was just chosen to share the title of "false counselor" in the list of leading "environmental sinners" compiled in the May issue of Vanity Fair on the newstands now (article "Dante's Inferno: Green Edition"; unfortunately, this sits behind the subscription wall, so you'll have to purchase the magazine for further details). Incidentally, several other frequent appearers on RC such as Fred Singer, Willie Soon, Sally Baliunas, James Inhofe, and Michael Crichton share in the award festivities. For a time, Lindzen set himself apart from this latter sort of contrarian; his scientific challenges were often thoughtful and his hypotheses interesting, if one-sided - he never met a negative feedback he didn't like. Sadly, it has become clear that those days are gone.

The investment required to decarbonise the energy system (for the UK, about £10billion per year for 25 years) can help to provide for the retirement of the baby boomer generation. By guaranteeing future electricity prices, private sector investment can provide energy security and avoid war. We can eliminate taxes on working families and business investment and instead penalise coal, crude oil, and gas as they enter the country.

Hello and Welcome to the Zero Carbon Group Website!

We hope that you like the new site!

Thanks and best regards,

Stephen

P.S. We want to avoid the whole world looking like Death Valley:

A lot of what gets discussed here in relation to the greenhouse effect is relatively simple, and yet can be confusing to the lay reader. A useful way of demonstrating that simplicity is to use a stripped down mathematical model that is complex enough to include some interesting physics, but simple enough so that you can just write down the answer. This is the staple of most textbooks on the subject, but there are questions that arise in discussions here that don't ever get addressed in most textbooks. Yet simple models can be useful there too.

I'll try and cover a few 'greenhouse' issues that come up in multiple contexts in the climate debate. Why does 'radiative forcing' work as method for comparing different physical impacts on the climate, and why you can't calculate climate sensitivity just by looking at the surface energy budget. There will be mathematics, but hopefully it won't be too painful.

So how simple can you make a model that contains the basic greenhouse physics? Pretty simple actually. You need to account for the solar radiation coming in (including the impact of albedo), the longwave radiation coming from the surface (which depends on the temperature) and some absorption/radiation (the 'emissivity') of longwave radiation in the atmosphere (the basic greenhouse effect). Optionally, you can increase the realism by adding feedbacks (allowing the absorption or albedo to depend on temperature), and other processes - like convection - that link the surface and atmosphere more closely than radiation does. You can skip directly to the bottom-line points if you don't want to see the gory details.

The Greenhouse Effect

The basic case is set up like so: Solar radiation coming in is , where is the albedo, TSI the solar 'constant' and the factor 4 deals with the geometry (the ratio of the area of the disk to the area of the sphere). The surface emission is where is the Stefan-Boltzmann constant, and is the surface temperature and the atmospheric radiative flux is written , where is the emissivity - effectively the strength of the greenhouse effect. Note that this is just going to be a qualitative description and can't be used to quantitatively estimate the real world values.

There are three equations that define this system - the energy balance at the surface, in the atmosphere and for the planet as a whole (only two of which are independent). We can write the equations in terms of the energy fluxes (instead of the temperatures) since it makes the algebra a little clearer.

Surface:
Atmosphere:
Planet:

The factor of two for A (the radiation emitted from the atmosphere) comes in because the atmosphere radiates both up and down. From those equations you can derive the surface temperature as a function of the incoming solar and the atmospheric emissivity as:

If you want to put some vaguely realistic numbers to it, then with S=240 W/m² and =0.769, you get a ground temperature of 288 K - roughly corresponding to Earth. So far, so good.

Point 1: It's easy to see that the G (and hence ) increases from S to 2S as the emissivity goes from 0 (no greenhouse effect) to 1 (maximum greenhouse effect) i.e. increasing the greenhouse effect warms the surface.

This is an extremely robust result, and indeed has been known for over a century. One little subtlety, note that the atmospheric temperature is cooler than the surface - this is fundamental to there being a greenhouse effect at all. In this example it's cooler because of the radiative balance, while in the real world it's cooler because of adiabatic expansion (air cools as it expands under lower pressure) modified by convection.

Radiative Forcing

Now what happens if something changes - say the solar input increases, or the emissivity changes? It's easy enough to put in the new values and see what happens - and this will define the sensitivity of system. We can also calculate the instantaneous change in the energy balance at the top of the atmosphere as or changes while keeping the temperatures the same. This is the famed 'radiative forcing' you've heard so much about. That change (+ve going down) is:

where are the small changes in solar and change in emissivity respectively. The subscripts indicate the previous equilibrium values We can calculate the resulting change in G as:

so there is a direct linear connection between the radiative forcing and the resulting temperature change. In more complex systems the radiative forcing is a more tightly defined concept (the stratosphere or presence of convection make it a little more complex), but the principle remains the same:

Point 2: Radiative forcing - whether from the sun or from greenhouse gases - has pretty much the same effect regardless of how it comes about.

Climate Sensitivity

The ratio of is the sensitivity of to the forcing for this (simplified) system. To get the sensitivity of the temperature (which is the more usual definition of climate sensitivity, ), you need to multiply by i.e. . For the numbers given above, it would be about 0.3 C/(W/m²). Again, I should stress that this is not an estimate for the real Earth!

As an aside, there have been a few claims (notably from Steve Milloy or Sherwood Idso) that you can estimate climate sensitivity by dividing the change in temperature due to the greenhouse effect by the downwelling longwave radiation. This is not even close, as you can see by working it through here. The effect on due to the greenhouse effect (i.e. the difference between having and its actual value) is , and the downward longwave radiation is just , and dividing one by the other simply gives - which is not the same as the correct expression above - in this case implying around 0.2 C/(W/m2) - and indeed is always smaller. That might explain it's appeal of course (and we haven't even thought about feedbacks yet...).

Point 3: Climate sensitivity is a precisely defined quantity - you can't get it just by dividing an energy flux by any old temperature.

Feedbacks

Now we can make the model a little more realistic by adding in 'feedbacks' or amplifying factors. In this simple system, there are two possible mechanism - a feedback on the emissivity or on the albedo. For instance, making the emissivity a function of temperature is analogous to the water vapour feedback in the real world and making the albedo a function of temperature could be analogous to the ice-albedo or cloud-cover feedbacks. We can incorporate the first kind of physics by making dependent on the temperature (or for arithmetical convenience). Indeed, if we take a special linear form for the temperature dependence and write:

then the result we had before is still a solution (i.e. ). However, the sensitivity to changes (whether in the greenhouse effect or solar input) will be different and will depend on . The new sensitivity will be given by

So if is positive, there will be an amplification of any particular change, if it's negative, a dampening i.e. if water vapour increases with temperature that that will increase the greenhouse effect and cause additional warming. For instance, , then the sensitivity increases to 0.33 C/(W/m²). We could do a similar analysis with a feedback on albedo and get larger sensitivities if we wanted. However, regardless of the value of the feedbacks, the fluxes before any change will be the same and that leads to another important point:

Point 4: Climate sensitivity can only be determined from changes to the system, not from the climatological fluxes.

Summary

While this is just a simple model that is not really very Earth-like (no convection, no clouds, only a single layer etc.), it does illustrate some relevant points which are just as qualitatively true for GCMs and the real world. You should think of these kinds of exercises as simple flim-flam detectors - if someone tries to convince you that they can do a simple calculation and prove everyone else wrong, think about what the same calculation would be in this more straightforward system and see whether the idea holds up. If it does, it might work in the real world (no guarantee though) - but if it doesn't, then it's most probably garbage.

N.B. This is a more pedagogical and math-heavy article than most of the ones we post, and we aren't likely to switch over exclusively to this sort of thing. But let us know if you like it (or not) and we'll think about doing similar pieces on other key topics.

The release of the IPCC Working Group II summary report (on climate change impacts) lead to a large number of stories on climate change in the media and, inevitably, lots of requests for media appearances for climate scientists on the journalists' Rolodex. On the same day, there was a short article in Science on the 'framing' of science communication.

The Science piece, by Scibloggers Chris Mooney and Matt Nisbet, make the point that the way science is expressed in public makes a difference to how it is received. So much, so uncontroversial. However, it generated some trenchant counter-arguments, (and counter-counter-arguments), possibly because they start off criticising a bit of a strawman 'scientist' who thinks that 'if only laypeople better understood technical complexities... controversies would subside'. It's certainly possible that such people exist, however, they are unlikely to be found among the scientists who are active in trying to communicate to the public. However, instead of arguing about this in a rather abstract way, I thought I'd illustrate the issue by discussing three interviews I did last Thursday and Friday in relation to the IPCC WG II release.

I was asked to do three TV appearances to discuss the upcoming report: CNN (World News Tonight), Bloomberg Media (Peter Cook's Money and Politics) and the Weather Channel. Each interview was very different - CNN and the Weather Channel pre-taped them, Bloomberg was live. CNN's interview was from a news reporter who knew the basics, who asked questions that she was interested in and ended up with answers that were comprehensible at the level of the average viewer. The Weather Channel interview was done by Heidi Cullen who is much more versed in the topic (and has a climate science background) and is very aware both of the real issues and the fake 'pseudo-debates' that often surround the topic. Her questions were spot on, but possibly at a higher level than would be appropriate on CNN. In both cases, the details of the new report were of less interest than the overall message that the IPCC reports and climate science community are giving.

The Bloomberg producers (who come with a very 'Wall Street' focus/attitude) however, still see this as a partisan political debate and while they had a brief factual intro from their reporter, they followed it with a spokesman from CEI, Christopher Horner - author of the "Incorrect guide to climate change" (I've possibly got the book title slightly wrong), - and then me. As you might expect, the subsequent 5 minute 'conversation' was neither informative nor entertaining, and I doubt that anyone watching was the least bit swayed, intrigued or had their curiosity piqued or their prejudices reinforced. Horner zipped through his grab-bag of talking points (mostly focussed on the imagined failings of the IPCC process), which probably went over the heads of any civilians watching, while I tried to stick to the point that climate change impacts have started and will likely get worse (when I could get a word in edgewise).

So what does this tell us about the 'framing' of the issue? First off, the interviewee doesn't get to change the 'frame' in a 5 minute TV interview - however often you are on. Instead the frame is imposed mostly from the editorial and production decisions. It's easy to see that the CNN and Weather Channel producers see climate change story in a 'news event' frame, for which they get outside expertise to explain some of the finer points. Bloomberg see this in a 'political controversy' frame and set up their interviews accordingly. Horner would like the frame to be about 'political/scientific corruption' which clearly appeals to some, but since he asks you to believe lawyers over scientists, it's unlikely to get very far (scientists are roughly 3 times more 'trusted' than lawyers). Given the other channels decisions' and the House/Senate hearing a couple of weeks ago, I think that this 'framing' has probably had its day but will likely linger on in some corners for a while.

How do frames shift then? Despite what some might think, it is a matter of education - not of the general public though (as welcome as that would be) - but of the gatekeepers: the journalists, editors and producers. Communication efforts are much more likely to succeed if they target the people who communicate for a living, rather than the general public directly. While the overall frame for climate change has clearly moved from 'controversy' to 'news event', there are still sub-issues that advocates for specific policy changes are fighting over - those are however, more subtle and aren't so much of a problem of 'pure' science communication, and so I'll leave it for others to discuss those.

http://www.realclimate.org/index.php?p=227

Methane hydrates and global warming (2005)

There is an enormous amount of methane (CH4) on earth frozen into a
type of ice called methane hydrate. Hydrates can form with almost any
gas and consist of a ‘cage’ of water molecules surrounding the gas.
(The term ‘clathrate’ more generally describes solids consisting of
gases are trapped within any kind of cage while hydrate is the
specific term for when the cage is made of water molecules). There are
CO2 hydrates on Mars, while on Earth most of the hydrates are filled
with methane. Most of these are in sediments of the ocean, but some
are associated with permafrost soils.

Methane hydrates would seem intuitively to be the most precarious of
things. Methane hydrate melts if it gets too warm, and it floats in
water. Methane is a powerful greenhouse gas, and it degrades to CO2,
another greenhouse gas which accumulates in the atmosphere just as
fossil fuel CO2 does. And there is a lot of it, possibly more than the
traditional fossil fuel deposits. Conceivably, climate changes could
affect these deposits. So what do we know of the disaster-movie
potential of the methane hydrates?

Ocean hydrates. Most of the methane hydrate is in sediments of the
ocean. Of that, most is what can be called the stratigraphic-type
deposits. Organic carbon from plankton is buried over millions of
years. Hundreds of meters below the sea floor, bacteria produce
methane from the dead plankton. If methane is produced quickly enough,
some of it will freeze into methane hydrates. This type of deposit
holds thousands of gigatons of carbon as methane [Buffett and Archer,
2004; Milkov, 2004]. For comparison, the most abundant type of
traditional fossil fuel is coal, which is typically credited with
about 5000 Gton C [Rogner, 1997].

Sometimes the methane moves around in the earth, and collects
someplace, forming what are called structural hydrate deposits. The
Gulf of Mexico, for example, is basically a leaky oil field [MacDonald
et al., 2005]. One implication of gas moving around and pooling like
this is that the hydrate concentration can be higher, even to the
point of what they call massive deposits, lumps of nearly pure
hydrate. The second bottom line is that the hydrate can be found much
closer to the sea floor, and even on the sea floor.

Hydrate melts if it gets too warm. The ocean is cold enough in a depth
range from say 500 meters down (200 meters in the Arctic). Below the
sea floor, the temperature increases with depth, along the geothermal
temperature gradient. At some depth it becomes too warm for hydrate,
so hydrate melts if it becomes buried deeper than this depth. There is
often a layer of bubbles beneath the hydrate stability zone. The
bubbles reflect seismic sound waves, and show up clearly in seismic
surveys around the world [Buffett, 2000]. Hills and valleys of the
bubble layer follow hills and valleys of the sea floor, so this layer
is called a bottom-simulating reflector (BSR).

Now let’s warm up the water at the top of the sediment column.
Ultimately, the new temperature profile will have nearly the same
slope as before, the geotherm. The hydrate stability zone will get
thinner with an increase in the sediment column temperature. The
important thing to note is that it gets thinner from the bottom, not
from the top. Hydrate at the base of the original stability zone finds
itself melting.

If the stability zone still exists, it will be shallower in the
sediment column than the newly released methane bubbles, and so it
could act like a cold trap to prevent the released methane gas from
escaping. However, seismic studies often show ‘wipeout zones’ where
the BSR is missing, and all of the layered structure of the sediment
column above the missing BSR is smoothed out. These are thought to be
areas where gas has broken through the structure of the sediment to
escape to the ocean [Wood et al., 2002]. One theory is that upward
migration of fluid carries with it heat, preventing the methane from
freezing as it travels through the nominal stability zone. The
sediment surface of the world’s ocean has holes in it called pockmarks
[Hill et al., 2004], interpreted to be what these gas explosions look
like from the surface.

And there is the possibility of landslides. When hydrate melts and
produces bubbles, there is an increase in volume. The idea is that the
bubbles might lift the grains off of each other, destabilizing the
sediment column. The largest submarine landslide known is off the
coast of Norway, called Storegga [Bryn et al., 2005; Mienert et al.,
2005]. The slide excavated on average the top 250 meters of sediment
over a swath hundreds of kilometers wide, stretching half-way from
Norway to Greenland. There have been comparable slides on the
Norwegian margin every approximately 100 kyr, synchronous with the
glacial cycles [Solheim et al., 2005]. The last one occurred 2-3 kyr
years after the stability zone thinned due to increasing water
temperature [Mienert et al., 2005], about 8150 years ago. The slide
started at a few hundred meters water depth, just off the continental
slope, where Mienert calculates the maximum change in HSZ. The
Storegga slide area today contains methane clathrate deposits as
indicated by a seismic BSR corresponding to the base of the HSZ at
200-300 meters, and pockmarks indicating gas expulsion from the
sediment.

However, there is another also apparently plausible hypothesis for
Storegga, which doesn’t involve hydrates at all. This is the rapid
accumulation of glacial sediment shed by the Fennoscandian ice sheet
[Bryn et al., 2005]. Rapid sediment loading traps pore water in the
sediment column faster than it can be expelled by the increasing
sediment load. At some point, the sediment column floats in its own
porewater. This mechanism has the capacity to explain why the
Norwegian continental margin, of all places in the world, should have
landslides synchronous with climate change.

The Storegga slide generated a tsunami in what is now the United
Kingdom, but it does not appear to have had any climate connections.
It was not a catastrophic amount of methane loss. The volume of
sediment moved was about 2500 km3. Assuming 1% hydrate by pore water
volume were released on average from the slide volume, you get a
methane release of about 0.8 Gton of C. Even if all of the hydrate
made it to the atmosphere, it would have had a smaller climate impact
than a volcanic eruption (I calculated the methane impact on the
radiative budget here). Actually, the truth be told, the Storegga
slide occurred spookily close in time to the 8.2k climate event, but
there doesn’t appear to be any connection. The 8.2k event was a
century-long cool interval, most probably in response to fresh-water
release from Glacial Lake Aggasiz to the North Atlantic and was
coincident with a ~75 ppbv drop in methane, not a rise.

Methane can leave the sediment in three possible forms: dissolved,
bubbles, and hydrate. Dissolved methane is chemically unstable in the
oxic water column of the ocean, but it has a lifetime of decades
(shorter in high-flux environments) [Valentine et al., 2001], so if
the methane is released shallow enough in the ocean, it has a good
chance of escaping to the atmosphere. Bubbles of methane are typically
only able to rise a few hundred meters before they dissolve. Hydrate
floats in water just like regular ice floats in water, carrying
methane to the atmosphere much more efficiently than bubbles [Brewer
et al., 2002].

For most parts of the ocean, melting of hydrates is a slow process. It
takes decades to centuries to warm up the water 1000 meters down in
the ocean, and centuries more to diffuse that heat down into the
sediment where the base of the stability zone is. The Arctic Ocean may
be a special case, because of the shallower stability zone due to the
colder water column, and because warming is expected to be more
intense in high latitudes.

Permafrost. You’ve maybe read about permafrost in the paper a lot
lately. Permafrost soils are defined as those which remain frozen
year-round (actually, the technical definition is a soil which has
been frozen for the last two years). There is sometimes a zone near
the sediment surface that thaws in the summer. In the permafrost
literature, this zone is called the active zone, and it has been
observed to be getting larger with time [Sazonova et al., 2004].
Melting of surface soils is one reason why the high latitude Arctic is
expected to be a part of the land surface that responds most
dramatically to climate change [Bala et al., 2005]. The other reason
is that temperature changes are more dramatic in high latitudes than
the global average, especially high northern latitudes. There has been
a stream of anecdotal reports of the effects of melting permafrosts on
the Arctic landscape, tilted buildings and “drunken forests” near
Fairbanks, for example [Pearce, 2005; Stockstad, 2004]. Much of the
Alaskan oil pipeline is anchored in permafrost soils.

Hydrates are sometimes associated with permafrost deposits, but not
too close to the soil surface, because of the requirement for high
pressure. The other factor that determines whether you find hydrate is
the permeability of the soils. Sometimes freezing, flowing groundwater
creates a sealed ice layer in the soil, which can elevate the pressure
in the pore space below. Hydrate in a one permafrost core [Dallimore
and Collett, 1995] was reported below sealed ice layers. Lakes have
been reported to suddenly drain away as some subsurface sealed ice
layer is apparently breached.

The grand-daddy of subsurface sealed ice layers is a very large
structure in Siberia called the ice complex [Hubberten and
Romanovskii, 2001]. The most important means of eroding the ice
complex is laterally, by a melt-erosion process called thermokarst
erosion [Gavrilov et al., 2003]. The ice layer is exposed to the
warming waters of the ocean. As the ice melts, the land collapses,
exposing more ice. The northern coast of Siberia has been eroding for
thousands of years, but rates are accelerating. Entire islands have
disappeared in historical time [Romankevich, 1984]. Concentrations of
dissolved methane on the Siberian shelf reached 25 times higher than
atmospheric saturation, indicating escape of methane from coastal
erosion into the atmosphere [Shakhova et al., 2005]. Total amounts of
methane hydrate in permafrost soils are very poorly known, with
estimates ranging from 7.5 to 400 Gton C (estimates compiled by
[Gornitz and Fung, 1994]).

The Future. The juiciest disaster-movie scenario would be a release of
enough methane to significantly change the atmospheric concentration,
on a time scale that is fast compared with the lifetime of methane.
This would generate a spike in methane concentration. For a scale of
how much would be a large methane release, the amount of methane that
would be required to equal the radiative forcing of doubled CO2 would
be about ten times the present methane concentration. That would be
disaster movie. Or, the difference between the worst case IPCC
scenario and the best conceivable ‘alternative scenario’ by 2050 is
only about 1 W/m2 mean radiative energy imbalance. A radiative forcing
on that order from methane would probably make it impossible to remain
below a ‘dangerous’ level of 2 deg above pre-industrial. I calculate
here that it would take about 6 ppm of methane to get 1 W/m2 over
present-day. A methane concentration of 6 ppm would be a disaster in
the real world.

The atmosphere currently contains about 3.5 Gton C as methane. An
instantaneous release of 10 Gton C would kick us up past 6 ppm. This
is probably an order of magnitude larger than any of the catastrophes
that anyone has proposed. Landslides release maybe a gigaton and
pockmark explosions considerably less. Permafrost hydrates are
melting, but no one thinks they are going to explode all at once.

There is an event documented in sediments from 55 million years ago
called the Paleocene Eocene Thermal Maximum, during which (allegedly)
several thousand Gton C of methane was released to the atmosphere and
ocean, driving 5 degrees C warming of the intermediate depth ocean. It
is not easy to constrain how quickly things happen so long ago, but
the best guess is that the methane was released over perhaps a
thousand years, i.e. not catastrophically [Zachos et al., 2001;
Schmidt and Shindell, 2003].

The other possibility for our future is an increase in the year-in,
year-out chronic rate of methane emission to the atmosphere. The
ongoing release of methane is what supplies, and determines the
concentration of, the ongoing concentration of methane in the
atmosphere. Double the source, and you’d double the concentration,
more or less. (A little more, actually, because the methane lifetime
increases.) The methane is oxidized to CO2, another greenhouse gas
that accumulates for hundreds of thousands of years, same as fossil
fuel CO2 does. Models of chronic methane release often show that the
accumulating CO2 contributes as much to warming as does the transient
methane concentration.

Anthropogenic methane sources, such as rice paddies, the fossil fuel
industry, and livestock, have already more than doubled the methane
concentration in the atmosphere from pre-industrial levels. Currently
methane levels appear stable, but the reasons for this relatively
recent phenomena are not yet clear. The amount of permafrost hydrate
methane is not known very well, but it would not take too much
methane, say 60 Gton C released over 100 years, to double atmospheric
methane yet again. Peat deposits may be a comparable methane source to
melting permafrost hydrate. When peat that has been frozen for
thousands of years thaws, it still contains viable populations of
methanotrophic bacteria [Rivkina et al., 2004] that begin to convert
the peat into CO2 and CH4. It’s not too difficult to imagine 60 Gton C
over 100 years from peat, either. Changes in methane production in
existing wetlands and swamps due to changes in rainfall and
temperature could also be important. Ocean hydrates have also been
forecast to melt, but only slowly [Harvey and Huang, 1995]. Places to
watch would seem to be the Arctic and the Gulf of Mexico.

So, in the end, not an obvious disaster-movie plot, but a potential
positive feedback that could turn out to be the difference between
success and failure in avoiding ‘dangerous’ anthropogenic climate
change. That’s scary enough.

I have submitted a more detailed review of hydrates and climate change
for peer review and publication, which can be accessed here.

Bala, G., K. Caldeira, A. Mirin, M. Wickett, and C. Delira,
Multicentury changes to the global climate and carbon cycle: Results
from a coupled climate and carbon cycle model, Journal of Climate, 18,
4531-4544, 2005.
Brewer, P.G., C. Paull, E.T. Peltzer, W. Ussler, G. Rehder, and G.
Friederich, Measurements of the fate of gas hydrates during transit
through the ocean water column, Geophysical Research Letters, 29 (22),
2002.
Bryn, P., K. Berg, C.F. Forsberg, A. Solheim, and T.J. Kvalstad,
Explaining the Storegga Slide, Marine and Petroleum Geology, 22 (1-2),
11-19, 2005.

Buffett, B., and D.E. Archer, Global inventory of methane clathrate:
Sensitivity to changes in environmental conditions, Earth and
Planetary Science Letters, 227, 185-199, 2004.
Buffett, B.A., Clathrate hydrates, Annual Review of Earth and
Planetary Sciences, 28, 477-507, 2000.
Dallimore, S.R., and T.S. Collett, Intrapermafrost Gas Hydrates from a
Deep Core-Hole in the Mackenzie Delta, Northwest-Territories, Canada,
Geology, 23 (6), 527-530, 1995.
Gavrilov, A.V., X.N. Romanovskii, V.E. Romanovsky, H.W. Hubberten, and
V.E. Tumskoy, Reconstruction of ice complex remnants on the eastern
Siberian Arctic Shelf, Permafrost and Periglacial Processes, 14 (2),
187-198, 2003.
Gornitz, V., and I. Fung, Potential distribution of methane hydrate in
the world’s oceans, Global Biogeochemical Cycles, 8, 335-347, 1994.
Harvey, L.D.D., and Z. Huang, Evaluation of the potential impact of
methane clathrate destabilization on future global warming, J.
Geophysical Res., 100, 2905-2926, 1995.
Hill, J.C., N.W. Driscoll, J.K. Weissel, and J.A. Goff, Large-scale
elongated gas blowouts along the US Atlantic margin, Journal of
Geophysical Research-Solid Earth, 109 (B9), 2004.
Hubberten, H.W., and N.N. Romanovskii, Terrestrial and offshore
permafrost evolution of the Laptev sea region during the last
Pleistocene-Holocene glacial-eustatic cycle, in Permafrost response on
economic develoopment, environmental security and natural resources,
edited by R. Paepa, and V. Melnikov, pp. 43-60, Klewer, Amsterdam,
2001.
MacDonald, I.R., L.C. Bender, M. Vardaro, B. Bernard, and J.M. Brooks,
Thermal and visual time-series at a seafloor gas hydrate deposit on
the Gulf of Mexico slope, Earth and Planetary Science Letters, 233
(1-2), 45-59, 2005.
Mienert, J., M. Vanneste, S. Bunz, K. Andreassen, H. Haflidason, and
H.P. Sejrup, Ocean warming and gas hydrate stability on the
mid-Norwegian margin at the Storegga Slide, Marine and Petroleum
Geology, 22 (1-2), 233-244, 2005.
Milkov, A.V., Global estimates of hydrate-bound gas in marine
sediments: how much is really out there?, Earth-Science Reviews, 66
(3-4), 183-197, 2004.
Pearce, F., Climate warning as Siberia melts, New Scientist, Aug. 11, 2005.
Rivkina, E., K. Laurinavichius, J. McGrath, J. Tiedje, V.
Shcherbakova, and D. Gilichinsky, Microbial life in permafrost, in
Space Life Sciences: Search for Signatures of Life, and Space Flight
Environmental Effects on the Nervous System, pp. 1215-1221, 2004.
Rogner, H.-H., An assessment of world hydrocarbon resources, Annu.
Rev. Energy Environ., 22, 217-262, 1997.
Romankevich, E.A., Geochemistry of Organic Matter in the Ocean,
Springer, New York, 1984.
Sazonova, T.S., V.E. Romanovsky, J.E. Walsh, and D.O. Sergueev,
Permafrost dynamics in the 20th and 21st centuries along the East
Siberian transect, Journal of Geophysical Research-Atmospheres, 109
(D1), 2004.
Shakhova, N., I. Semiletov, and G. Panteleev, The distribution of
methane on the Siberian Arctic shelves: Implications for the marine
methane cycle, Geophysical Research Letters, 32 (9), 2005.
Solheim, A., K. Berg, C.F. Forsberg, and P. Bryn, The Storegga Slide
complex: repetitive large scale sliding with similar cause and
development, Marine and Petroleum Geology, 22 (1-2), 97-107, 2005.
Schmidt, G.A., and D.T. Shindell. Atmospheric composition, radiative
forcing, and climate change as a consequence of a massive methane
release from gas hydrates. Paleoceanography 18, no. 1, 1004, 2003.
Stockstad, E., Defrosting the carbon freezer of the North, Science,
304, 1618-1620, 2004.
Valentine, D.L., D.C. Blanton, W.S. Reeburgh, and M. Kastner, Water
column methane oxidation adjacent to an area of active hydrate
dissociation, Eel River Basin, Geochimica Et Cosmochimica Acta, 65
(16), 2633-2640, 2001.
Wood, W.T., J.F. Gettrust, N.R. Chapman, G.D. Spence, and R.D.
Hyndman, Decreased stability of methane hydrates in marine sediments
owing to phase-boundary roughness, Nature, 420 (6916), 656-660, 2002.
Zachos, J.C., M. Pagani, L. Sloan, E. Thomas, and K. Billups, Trends,
rhythms, and abberations in global climate 65 Ma to Present, Science,
292, 686-693, 2001.

Guest commentary by Figen Mekik – Grand Valley State University

“But Figen, humid air feels oppressive, heavy!” students told me, almost in unison. A very treasured moment indeed. I just got a glimpse of probably a long held misconception: water vapor is heavier than dry air. So, we took out our periodic tables and calculators, and went on to calculate the molecular weight of H₂O and how it compares to that of N₂ and O₂ (most of the atmosphere). Happy that I corrected a major fallacy, I didn’t see the rest coming.

Apparently, there are many other sinister fallacies lurking just underneath the surface of the heavy wet air idea. One student asked “is the formula for water vapor the same as for liquid water?” and was astonished to find out that it is always H₂O regardless of phase, even in ice! I said “we like to keep things simple in science” and a couple of ladies giggled “as if!”

Then another admitted that he always thought water split into H₂ and O₂ upon evaporation which would make wet air heavy. Another student answered him with “No way man. When water vapor condenses to liquid, the molecules get bigger which is why liquid water is heavier than vapor.” So we had a long discussion about molecular dynamics of evaporation and condensation. Also, once I helped the students realize the stark contrast between what they think they know (water vapor is heavy) and something else they know from the Weather Channel (low pressure means rain), the cognitive dissonance (the psychological tension created by conflicting knowledge) drove them to question both “bits of knowledge” and to adjust their ideas. By the end of the hour, they were saying this is SOOO weird, humid air rises. Who knew!

Here are some other common and very tenacious misconceptions:

[1] Seasons are caused by cyclical changes in Earth’s proximity to the Sun. The main causes underlying this one likely are that [a] intuitively it makes sense and [b] textbooks frequently exaggerate the eccentricity of Earth’s orbit to the extreme that such an idea is logical. The problem is this misconception is extremely popular, from kindergarten to high school physics teachers. A very confused young man once told me openly “Well, my third grade teacher told me that the Earth’s axis is tilted and that is why we get different seasons and it’s winter in the northern hemisphere, when it’s summer in the southern hemisphere. My high school earth science teacher told me during the summer we are closer to the Sun and summers are hot everywhere. Now you are saying my grade school teacher was right all along. And there is all this hype about sunspot activity being the real cause behind global warming. Since the Sun causes our seasons for whatever reason, that sounds believable to me. But you say it’s CO₂ in the atmosphere causing global warming. How do I know I can trust you?”

He has a point! And it is very difficult to address the inconsistencies in his education convincingly. I could have told him about my PhD and that I am a climate scientist, but that really doesn’t have much currency in such situations. So I acknowledged that he has a valid point and devoted the next month to demonstrations and data and error margin analysis to empower the students to the point that they could understand the science for themselves. We couldn’t cover coastal geology that semester because we ran out of time, but I think it was worth it anyway.

[2] The hole in the ozone layer and atmospheric pollution (including but not limited to aerosols) cause global warming. Like the previous one, this one is also very tenacious and difficult to dispel because it is often presented this way in the media and most primary and secondary school teachers share the same fallacy. Perhaps one of the underlying faulty notions here is that the Earth receives heat from the Sun, instead of radiation. So, the thinking here is that the ozone layer shields our planet from the Sun’s harmful rays and its heat. And because there is a hole in the ozone layer, the extra heat seeps in and gets stuck under the ozone layer causing the greenhouse effect. I know, yikes!! I try to dispel this misconception by explaining that though the sun is indeed quite hot, there is all this empty space between the Sun and our planet and heat travels to Earth as infrared radiation from the sun, but the Sun's output of infrared is only a fraction of its output as visible light. Energy from the sun mostly reaches us as visible light and ultraviolet radiation. (Minor edit to remove confusion with sensible heat and radiation. Sorry about that!).

However, the notion that global warming and ozone depletion are linked is not entirely wrong. As was discussed earlier on RealClimate (Ozone depletion and global warming), original CFC’s as well as ozone itself are powerful greenhouse gases and stratospheric cooling caused by the increase in atmospheric CO₂ actually accelerates ozone loss there. Even the replacement gases to be used in lieu of CFCs may have significant greenhouse warming potential. BUT, ozone depletion (“the hole in the ozone layer”) does not cause global warming.

This discussion eventually lends its way to a discussion of aerosols (see Aerosols: the Last Frontier) and although aerosols tend to scatter or absorb incoming solar radiation (hence a warming effect), their net effect is in the direction of cooling because they have a positive influence on the nucleation of clouds which increases our planet’s albedo (ability to reflect light).

[3] The greenhouse effect and global warming are the same thing. This is another yikes!! Perhaps the root of the problem here is that the discussion of the greenhouse effect in the classroom is often tightly linked with that of global warming. It needs to be explicitly pointed out to students that without the greenhouse effect our planet’s surface would be about 30 degrees C cooler and with wild differences in temperature between night and day. Not exactly habitable. But anthropogenic global warming is caused by the human-induced increase of greenhouse gases in the atmosphere since the Industrial Revolution, particularly CO₂. Most of the past changes in climate on glacial-interglacial timescales can be explained by invoking changes in solar activity and greenhouse gas concentrations in the atmosphere, sure. But the warming we have been experiencing in the last few decades cannot be explained if we do not include the effect of greenhouse gases released by human activities (see the IPCC 4^th Assessment SPM, and Avery and Singer: Unstoppable Hot Air, just to name a couple).

[4] Toilets flush in opposite directions in the northern and southern hemispheres. This one is kind of a pedagogically useful misconception because although it is absolutely wrong, the idea behind it is correct and it is primarily a matter of scale. Having said that, I find the Coriolis effect to be one of the most challenging topics for students to grasp as soon as we move beyond its initial descriptive definition. There is often lots of confusion between “to the right” and “to the east” in the northern hemisphere. Plus when we add another dimension to the mix (vertical) in discussing tropical hurricanes, this becomes a serious barrier to understanding. So, I try to avoid any directional terms, like east or west as well as clockwise or counter-clockwise. Not because students are too young to know a non-digital traditional clock, but because from satellite images hurricanes look like they are rotating counter-clockwise. Really can’t argue with what the students are seeing for themselves. But if we keep the terms simple, “moving objects in the northern hemisphere are deflected to the right within the frame of reference of the moving object,” it becomes a little easier to understand, though still challenging. Another challenge here is that the Coriolis effect comes across as a force and it is difficult for students who have not had physics to distinguish between a force and a deflection (an effect).

Perhaps you are now thinking “this may be true in some university in west Michigan but surely in other, more prestigious universities the students know better!” If only this were true. A Private Universe is a video documenting lingering misconceptions among Harvard graduates about the causes behind seasons and lunar phases. The problem is misconceptions are hard to detect because most students are adept at answering questions with exactly what the teacher wants to hear and with correct terminology but without any real understanding of the science. After nine years of collegiate teaching I now know to encourage a casual “say whatever is on your mind” attitude with students. This way, I am hoping to get them to inadvertently voice their misconceptions so I can address them.

And one may be tempted to think this is solely an American problem because the American system of education has been exposed to some serious criticism of late. Again, not so! It’s a global problem. Here are some examples from a couple of quick Google searches. Greek kindergarten teachers harbor deeply rooted confusion about the “ozone hole” and the “greenhouse effect;” while Greek primary school teachers think the ozone hole causes climate change. Australian university students believe a large portion of the ozone hole is over Australia and that the high rate of skin cancer is largely caused by this hole. Junior high school students in Israel seem to understand various processes within the hydrologic cycle, but believe its beginning point is the ocean and the end point is groundwater. And some Turkish in-service physics teachers believe that the moon does not rise and set while Turkish pre-service science teachers think summer is warmer than winter because the Earth is closer to the sun in the summer time.

How about you? Take this quiz to see where you stand Update: Apparently the quiz has been taken off line...

I think, however, there may be some room for improvement in the wording and explanations in this quiz because some questions are very obscure, ambiguous and Chicago-centric. I would like to know what commenters think about it.

Where do misconceptions come from? Personal experiences and intuitive understanding play a large part in fostering misconceptions, and most false notions are reinforced through school and the media. I would like to share with you this delightful and brief story of how personal experiences color the judgment of a bunch of 4^th graders about the nature of heat. They have a wise science teacher who broaches the topic with a question: “can you give me an example of something that is hot?” She is expecting answers like the Sun, or a stove or maybe even Britney Spears. But the students say sweaters, hats, and coats. One says “rugs are wicked hot.” The teacher says “when I touch your sweater it doesn’t feel hot.” The students say “Ooh, it’s a matter of time. With time it can be 200 degrees!” Hmmm.. Can you blame them? They spent at least nine years in cold Massachusetts winters and their parents and teachers always told them to put on their warm clothes.

Like this example, some of the problem underlying misconceptions stems from language. “Warm clothes” implies clothes that emit heat, “greenhouse gas” suggests greenhouses are warm because of their gas content, “the rise and set of the sun” suggests the sun is moving across the sky, not the earth is rotating on its axis, and “the theory of relativity” implies all things are relative when actually the theory is based on the constancy of the speed of light.

Let’s go back to our 4^th grade class to see how this very experienced teacher addressed the problem. She could just come right out and say “that’s ridiculous, you’re clothes don’t emit heat, they trap the heat your bodies emit.” That would certainly save time to cover more content; instead she decides to do something else (e.g. concept/inquiry based learning for the educators out there). She says “Tomorrow I want everyone to bring something hot from home.” The next day sweaters, scarves, hats and even a down sleeping bag arrive. The teacher puts a thermometer into each one and they wait until the next day for them to get hot on the inside. The students are convinced the down sleeping bag will be 400 degrees! They rush in the next morning and quickly check their thermometers. 68 degrees! They’re shocked. But convinced? Not a chance! They are not going to dismiss 9 years of personal experience just like that. “Cold air got in there!” says one little girl. “When I sit in the car with the windows up, it gets hot. We need to hide our clothes.” So sweaters and hats get put into drawers and closets with their thermometers snuggly in them. Another night goes by. The next day they rush in and check their thermometers again. Again 68 degrees! Except one student has 69 degrees. They all applaud. Still not convinced, after all there has been indication in the right direction! Several nights go by like this. Finally serious doubt begins to ensue. So the teacher says “I want everyone who believes clothes are hot to walk to this corner” and she points left; “and the ones who think clothes trap the heat our bodies emit to this corner” and she points right. Most of the students go to the right but three stubborn ones go to the left. Guess you will always have the denialists! But no matter what, these students experienced two things more important than heat: the scientific method in action and sometimes the way something feels is only that and not reality.

So, are misconceptions barriers to understanding or helpful pedagogical tools? That will largely depend on the individual teacher’s (professor’s) style and interests. But the important thing is to [1] challenge misconceptions, [2] demonstrate their faultiness through carefully devised experiments (ideally by the students), [3] help develop multiple working hypotheses to understand the meaning of the results of these experiments, [4] devise more experiments to test and retest each hypothesis, and [5] NEVER let a student leave the classroom with a diagnosed misconception uncorrected. And, perhaps the most effective method for eradicating misconceptions at every level is going to be investing large quantities of time, money and effort into educating primary and secondary school educators. NSF has many programs that fund such efforts, but much more effort is clearly needed on a global scale.

Disclaimer: I am not an educational psychologist. I am simply a college professor and ocean/climate scientist enjoying a rich and intense teaching career in the Geology Department at GVSU. Also, my anecdotes and all my quotations are intentionally fictionalized to protect the confidentiality of students. The ideas expressed in the quotes are amalgamations of multiple repeated ideas expressed to me from students, professors and colleagues alike since I started graduate school in 1991 at Middle East Technical University in Ankara, Turkey; and the misconceptions I mention are not unique to any of my students but are listed in over 7000 published misconceptions about science.

The already-reeling "consensus" supposedly linking climate change to CO2 is about to receive its final coup-de-grace from a remarkable new result announced in a press conference today by Dr. Ewe Noh-Watt of the New Zealand Institute of Veterinary Climatology [1]. Noh-Watt and his co-workers, describing work funded by a generous grant from the Veterinary Climate Science Coalition, declared "We have seen the future of climate -- and it is Sheep." Prof. Jean-Belliere Poisson d'Avril, star student of Claude Allegro Molto-Troppo (discoverer of the Tropposphere) reacted with the words, "Parbleu! C'est la meilleure chose depuis les baguettes tranchées!"

The hypothesis begins with the simple observation that most sheep are white, and therefore have a higher albedo than the land on which they typically graze (see figure below). This effect is confirmed by the recent Sheep Radiation Budget Experiment. The next step in the chain of logic is to note that the sheep population of New Zealand has plummeted in recent years. The resulting decrease in albedo leads to an increase in absorbed Solar radiation, thus warming the planet. The Sheep Albedo hypothesis draws some inspiration from the earlier work of Squeak and Diddlesworth [2] on the effect of the ptarmigan population on the energy balance of the Laurentide ice sheet. Noh-Watt hastens to emphasize that the two hypotheses are quite distinct, since the species of ptarmigan involved in the Squeak-Diddlesworth effect is now extinct.

The proof of the pudding is in the data, shown in the Figure below. Here, the Sheep Albedo Index is defined as the New Zealand Sheep population in each year, subtracted from the 2007 population. The index is defined that way because fewer sheep means lower albedo, and thus a positive radiative forcing. It can be seen that the recent warming can be explained entirely by the decline in the New Zealand sheep population, without any need to bring in any mysterious so-called "radiative forcing" from carbon dioxide, which doesn't affect the sunlight (hardly) anyway -- unlike Sheep Albedo. Some researchers have expressed surprise at the large effect from the relatively small radiative forcing attributable to New Zealand Sheep, or indeed to New Zealand as a whole. "This only shows the fallacy of the concept of Radiative Forcing, which is after all only a theory, not a fact," says Noh-Watt. "Evidently there are amplifying feedbacks at work which give the Sheep Albedo Index a disproportionate influence over climate."

"A real breakthrough was using the statistical technique pioneered by Frusen-Glädje and Haagendassen in their study of the solar-climate connection." said Noh-Watt "Just as in their case, to get a good match to the observed climate, we had to optimize our smoothing algorithm by smoothing some parts of the sheep record more than others, and then rescaling the results." The optimized smoothing was applied to the years 1975-1991. Noted skeptic Rasmus Benestad has criticized this technique as meaningless curve-bashing (see footnote [3] below), but according to Noh-Watt, " All these guys are interested in is getting rich by riding their bicycles to work and selling carbon credits to the EU."

Not everybody agrees with the Sheep Albedo Hypothesis. Leading the flock of skeptics is the New Zealand Sheep Farmers Guild. Their spokesman, Steve Ramsturf (no relation) was quoted as saying "Baaah, Humbug. No matter what goes wrong with the world, they're always trying to blame the poor New Zealand Sheep Farmer. First it was the methane belch tax. Now this Albedo thing. "

The recognition of the role of sheep albedo opens up some fascinating new possibilities for climate change mechanisms. There is in fact an important destabilizing feedback in the system: as climate gets warmer, there is less demand for wool sweaters and wooly underwear. Hence the sheep population tends to drop, leading to even more warming. In an extreme form, this can lead to a "runaway sheep-albedo feedback," which is believed to have led to the present torrid climate of Venus. Most researchers do not think this could happen on Earth, though. In fact, Oprah and Averell Chanteur, authors of the popular "Unstoppable" series (soon to be a major motion picture) say that the warming will usher in a new era of peace and prosperity, with less enslavement of domestic wool-bearing animals. The hypothesis is laid out in their forthcoming book, "Unstoppable Sheep, every five or six days," which expands on earlier popular titles in the series, such as "Unstoppable daylight, every 42 hours," "Unstoppable Summer, every 17 months, " and the ever-popular autobiographical work "Unstoppable nonsense, every two or three years."

However, Dirk Blitzen, noted researcher from Hogwartz Institute of Technology, has proposed an additional wrinkle on the sheep-albedo idea, which he calls the "sheep-Iris effect" (see Dasher et al. [4] for details). According to Blitzen, a reanalysis of Landsat images shows that as the climate gets warmer, sheep tend to huddle together less. Since wool has a lower emissivity than bare ground, the lack of huddling allows more infrared emission to escape from the ground, cooling the planet and stabilizing its climate. "Frankly, I don't see how the climate can change much at all," stated Blitzen in recent testimony before the House of Lords, "To be honest, at this point I have a little trouble figuring out how there can even be summer and winter. In the end, I think it will turn out to be a problem with the data." Ozark Junior College satellite expert Jhon Chrystal agrees; his new analysis of MSU satellite data in fact casts doubt on the "consensus" that summer and winter have different temperatures.

But the sheep story may not be as simple as it seems. Hendreck Svampmark of the Danish Institute for Solar-Sheep Interactions notes that at the same time the number of sheep has been going down, the number of cows (which have a lower albedo than sheep) has been going up. "We believe that what is really behind it all are Galactic Cowsmic Rays, which are transmuting sheep DNA into cow DNA." Svampmark hypothesizes a currently undetected particle flux, which he calls "Cowsmic," because there is no observed trend in any of the better-known components of the Galactic Cosmic Ray flux. "We are trying to get money to put sheep in dark-matter accelerators to test our hypothesis, but there's a hold-up with PETA. It's all a big conspiracy to protect the consensus, I say."

Footnotes:

[1] Noh-Watt, Ewe "Sheep-Albedo Feedback: A paradigm shift for climate change science." To be submitted to Readers' Digest, "Humor in Uniform" section.

[2] Squeak, P.P. & Diddlesworth, I.R. 1987. The influence of ptarmigan population dynamics on the thermal regime of the Laurentide Ice Sheet : the surface boundary condition. In eds Edwin D. Waddington & Joseph S. Walder, The Physical Basis of Ice Sheet Modelling (Proceedings of a symposium held during the XIX Assembly of the International Union of Geodesy and Geophysics at Vancouver, August 1987), p.381-384.

[3] Benestad, a well-known spoilsport, points out that without the "optimized" smoothing out of the sheep-albedo-dip in the 1970's, the correlation breaks down; it breaks down further if one looks at the pre-1966 record. His unprocessed version of the data is shown below:

[4] Dasher ON., Dantzer ON, Prantzer ON, Vixen ON, Comet ON, Cupid ON Donner . , and Blitzen, D.R , (2007) "Why does Rudolf's nose glow so bright? Infrared effects of mammalian herd behavior." Bull. Tromsø Inst. Reindeer Husbandry