Guest Post by Willis Eschenbach
It was hot here a couple of days ago. I walked past a huge aloe vera plant, taller than my head, that grows by our house. The heat radiating off of the plant was palpable. I could feel a wash of warm air over me as I stood downwind of it. For a while I thought about the curious ability of plants to heat the air around them, and then I let it go.
Figure 1. Solar absorber, natural style. Note how the design efficiently intercepts sunlight because of the spiral, uneven pattern of the leaves. Also note that the design keeps photons from escaping through the funnel-shaped nature of the leaf pattern. Finally, consider that when the plant emits IR from the inner leaves, it will be re-absorbed by outer leaves, perhaps a number of times. This gives the plant, in effect, a local “greenhouse effect” due to the multiple re-absorption of the IR. The leaf geometry also greatly slows down the passage of the air through the plant, once again increasing the local warming. The net of all of those is a warm plant, surrounded by warm air.
I was reminded of our aloe vera again when a friend sent me a copy of the paper “A Warm Miocene Climate at Low Atmospheric CO2 levels,” by Knorr et al. It reports the results of a climate model analysis of the Miocene, the period from about twenty-three million years ago up to five million years ago. It is in press at GRL (paywalled), but the results are discussed here.
In their abstract, we find (emphasis mine):
In this study we present climate simulations of the Late Miocene (11-7 Ma) with a preindustrial CO2 level, using a coupled atmosphere-ocean general circulation model (AOGCM). The simulated global mean surface temperature of ~17.8 ºC represents a significantly warmer climate than today. We have analyzed the relative importance of tectonic [shape and location of the continents] and vegetation changes as forcing factors. We find that the strongest temperature increase is due to the Late Miocene vegetation distribution, which is more than three times stronger than the impact induced by tectonic alterations. Furthermore, a combination of both forcing factors results in a global temperature increase which is lower than the sum of the individual forcing effects. Energy balance estimates suggest that a reduction in the planetary albedo and a positive water vapor feedback in a warmer atmosphere are the dominating mechanisms to explain the temperature increase. Each of these factors contributes about one half to the global temperature rise of ~3 K. Our results suggest that a much warmer climate during the Late Miocene can be reconciled with CO2 concentrations similar to pre-industrial values.
In looking at the effect of plants on the climate, I’d like to discuss the use of the models, how much weight we should put on their results, and how they could be improved.
The first rule of models says
All Models Are Wrong, But Some Models Are Useful
Their usefulness, of course, depends on their ability to replicate the reality which they are modeling. One issue with the models is that many of them still are not what I call “lifelike”. I discussed this problem of “lifelike” climate model results here. If the models do not act like the real climate, why should we believe them? Unfortunately, no one has ever instituted this kind of test to compare all of the models. It should be a part of a standard suite of climate model tests … dream on.
So at the moment we don’t know if the climate model used in this test gives a lifelike simulation of today, much less of ten million years ago. But I digress. The study says (emphasis mine):
We utilize the comprehensive AOGCM ECHAM5-MPIOM without any flux corrections [e.g. Jungclaus et al., 2006]. The atmosphere model ECHAM5 was used at T31 resolution (~3.75º) with 19 vertical levels. The ocean model MPIOM was run at an average resolution of ~3º with 40 vertical layers. Vegetation is a fixed factor represented by specifying different land surface parameters like albedo, roughness length, vegetation ratio, leaf area index and maximum soil water capacity.
Here we run into another modeling problem. They have set up the vegetation parameters to coincide with what we know of the Miocene landscape. This, of course, means that they are using vegetation as a forcing, rather than a feedback.
But we have been informed, over and over, that the vegetation is a feedback and never a forcing …
This is both a strength and a weakness of the models. We can make assumptions like where the vegetation grew and force things in the model to be a certain way. Then we can see what the effect of that on the results might be.
Unfortunately, the climate doesn’t work that way, where one thing holds steady while everything else changes. So even though we can get some insights, we have no assurance that the effect that we find is real. For example, we don’t know if the Miocene vegetation (which is specified) fits with what the model says were the climate patterns of that time.
Setting aside the manifold questions about the model, there were a couple of interesting parts of the study. The first was that they find that the main effect of the plants occurred through a change in the albedo, particularly for the Sahara. This is in accord with my experience of the aloe vera plant, where it was absorbing much more energy than the ground around it. In part this was because of the albedo of the plant being lower than the ground beneath, but in part it was from the geometry of the plant. (This latter effect is neglected in the model.)
The second interesting thing involves these two statements of theirs about the albedo:
The planetary albedo in MIO [the Miocene simulation] is reduced by ~0.014, which causes less shortwave reflection by the atmosphere and a warming.
and
Based on a zero-dimensional energy balance model [e.g. Budyko, 1969] the impact of α [albedo] and ε [effective long wave emissivity] can be quantified, each causing about one half of the global warming of ~3 K.
Assuming the same solar intensity as the present (345 W/m2), which the authors say that they have done, this change in albedo would result in a change in solar radiation of 0.014 times 345 = 4.83 W/m2. Given the temperature change of 1.5°C from the albedo change, this gives a climate sensitivity of:
1.5°C * 3.7 W m-2 per doubling_CO2 / 4.83 W m-2 = 1.15°C per doubling of CO2.
Me, I think that climate sensitivity is an illusion based on a misunderstanding of how climate works … but for those who believe in it, using Knorr et al’s figures and their concepts, that gives a very low sensitivity, well below the IPCC canonical figure. The IPCC AR4 Summary for Policymakers says (emphasis mine):
The equilibrium climate sensitivity is a measure of the climate system response to sustained radiative forcing. It is not a projection but is defined as the global average surface warming following a doubling of carbon dioxide concentrations. It is likely to be in the range 2 to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C.
“Very Unlikely”, in IPCC jargon, means less than 10% chance that the sensitivity is less than their minimum estimate of 1.5°C per doubling of CO2. Despite that, this study shows a sensitivity of about three-quarters of the IPCC minimum estimate …
So you’d think that the media headline from this study would be
“Climate Model Finds Extremely Low Climate Sensitivity”
Sadly, that might happen, but only in an alternate universe …
Best to all,
w.
Hi Willis,
if you did a careful analysis of my tables
http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming
-suggest you make hard copies –
you can make a no. of interesting observations
1) modern warming appears to be driven by an increase in maxima, not minima. It is the increase in maxima that happen during the day that drives up the average temp. and also that of the minima.
If it were minima (that happen during the night) pushing up the average temp.s we should agree that an increase in GHG’s was the cause of it. As it stands at the moment we have to conclude that the warming of our planet was largely natural.
2) Maxima increased both in the SH and the NH but if you look at average temps. (= Means) it appears that the global warming is not really global. It would seem that in the NH, which has most of the landmasses, some of the additional heat (most probably caused by more sunshine and/or less clouds) is being trapped.
3) The difference in the warming of the NH and the SH again proves that it is not the the increase in CO2 that is contributing to it. Namely the CO2 conc. is quickly everywhere the same on earth due to wind and diffusion. Therefore the warming should everywhere be the saem – if an increase in GHG’s were doing it.
4) The most likely cause that I find for some entrapment of heat in the NH is that it is due to additional vegetation.Namely if you look at my results of Tandil in Argentina, where there has been substantial de-forestation, you find it is actually cooling. In Norway and Scandanavia where there has been an increase in forests, there it is warming.
So, I think, yes, the increase in vegetation does trap some heat, leading to some increase in the average temperature.The question is how much? Why do they bring CO2 in the equation when clearly it has nothing to do with it, apart perhaps from working as an accelerator for growth. Could this warming not be easily determined in real big greenhouses with and without plants?
Robert of Ottowa wrote: Models are usful tools to assist thinking about a problem; they are qualitive in nature. No weight shold be given to their quantative outputs.
It depends on how accurate they are, what Willis calls “lifelike”. Dosing regimes for drugs are based on well-tested models; space exploration is based on well-tested models.
Thanks again Willis for a another clear-headed look at some climate numbers. Someone mentioned above the ability of forests to control their temperature. Here’s an abstract:
From Canada to the Caribbean: Tree leaves control their own temperature
June 11th, 2008
The temperature inside a healthy, photosynthesizing tree leaf is affected less by outside environmental temperature than originally believed, according to new research from biologists at the University of Pennsylvania.
Surveying 39 tree species ranging in location from subtropical to boreal climates, researchers found a nearly constant temperature in tree leaves. These findings provide new understanding of how tree branches and leaves maintain a homeostatic temperature considered ideal for photosynthesis and suggests that plant physiology and ecology are important factors to consider as biologists tap trees to investigate climate change.
Tree photosynthesis, according to the study, most likely occurs when leaf temperatures are about 21°C, with latitude or average growing-season temperature playing little, if any, role. This homeostasis of leaf temperature means that in colder climates leaf temperatures are elevated and in warmer climates tree leaves cool to reach optimal conditions for photosynthesis. Therefore, methods that assume leaf temperature is fixed to ambient air require new consideration.
“It is not surprising to think that a polar bear in northern Canada and a black bear in Florida have the same internal body temperature,” Brent Helliker, professor of biology in the School of Arts and Sciences at Penn, said. “They are endothermic mammals like us ,and they generate their own heat. However, to think that a black spruce in Canada and a Caribbean pine in Puerto Rico have the same average leaf temperature is quite astonishing, particularly since trees are most definitely not endothermic. Our research suggests that they use a combination of purely physical phenomena — like the cooling from water evaporation or the warming caused by packing a lot of leaves together — to maintain what looks like leaf-temperature homeostasis.”
Leaf temperature, cooled by the physiological and morphological techniques of evaporation, leaf angle or reflection and heated by a decrease in evaporation and an increase in the number of leaves per branch, can now be considered adaptations towards achieving homeostasis. Researchers do not suggest that tree canopies maintain a constant temperature through a day or a season, but rather that this ideal temperature is a long-term target value.
The research, published online in this week’s Nature, contradicts the longstanding assumption that temperature and relative humidity in an actively photosynthesizing leaf are coupled to ambient air conditions. For decades, scientists studying climate change have measured the oxygen isotope ratio in tree-ring cellulose to determine the ambient temperature and relative humidity of past climates. The assumption in all of these studies was that tree leaf temperatures were equal to ambient temperatures.
http://www.sciencecentric.com/news/article.php?q=08061131
Willis, as you know! Green plants are reflecting only green light and are absorbing the red and blue frequencies of the light spectrum, the chemical responsible for the absorption of light is called Chlorophyll, and it is this chemical that makes the plant appear green, and as our sun is more of a green-yellowish star, green plants do in fact radiate heat albeit mostly in the green frequencies of the spectrum, here’s a thought, the amount of heat radiating from an Aloe Vera plant should be easy to work out, simply measure the amount Chlorophyll per square centimeter and measure the wattage of between 520 – 565nm wavelength from the sun etc… then do some modeling, An interesting hypothetical Questions would be; Does the addition of more Chlorophyll per square centimeter increase the amount of heat radiating from an Aloe Vera plant?
And come to the conclusion that more Chlorophyll equates to more radiative heat and more radiative heat makes for a better habitat for living creatures and more creatures equal vital Co2 and more Co2 equates to more healthy greener plants and so on…
It’s lucky humans and other creatures came along and evolved to live in an oxygen and nitrogen atmosphere as plants have very nearly used up the entire supply of Co2.
(Note flowers turn red, pink and blues to absorb light from the green part of the spectrum, and therefor as a consequence die off before bearing seed)
“Imagine an Alien Planet…
One common question in Biology regarding plant life is to imagine an alien planet with a green sun. Would the plant life on that planet still be green? Naturally, through evolution we would expect the plant life to adapt to absorb whatever available light they can so if the main light source is dominantly green, the plant would almost definitely not be green in colour itself. In fact you could imagine the plant would be pink in order to fully absorb the green wavelengths.”
(NOTE: the first plants evolved in the oceans and are thought to have been purple)
A Purple Sun
“There are also some theories that when photosynthesis first developed our oceans were purple and our sun was purple. This would explain the absence of a green absorbing Chlorophyll in plants if this were true. It’s also worth noting that some plant do in fact have purple or very dark leaves which would suggest some species of plant do make an effort of absorbing different light waves although green coloured plants remain the most dominant type.”
I didn’t know that there are theories that our sun was purple, have you heard of these?
http://www.whycenter.com/why-are-plants-green/
@John Day:
Sorry, I posted my comment while yours was in moderation it seems. CAM was the first thing that jumped out at me when I saw the Aloe.
We can’t expect all plants to behave the same way – if Aloe was human, it would be a human who couldn’t sweat. How hot would a human get in strong sunlight if unable to sweat?
Sorry to stray off topic, but I was flabbergasted by something I just read:
http://online.wsj.com/article/…..32438.html
The most flabbergasting part; our energy policy is based on fantasy:
When it was Mr. Hamm’s turn to talk briefly with President Obama, “I told him of the revolution in the oil and gas industry and how we have the capacity to produce enough oil to enable America to replace OPEC. I wanted to make sure he knew about this.”
The president’s reaction? “He turned to me and said, ‘Oil and gas will be important for the next few years. But we need to go on to green and alternative energy. [Energy] Secretary [Steven] Chu has assured me that within five years, we can have a battery developed that will make a car with the equivalent of 130 miles per gallon.’” Mr. Hamm holds his head in his hands and says, “Even if you believed that, why would you want to stop oil and gas development? It was pretty disappointing.”
@ur momisugly Don Monfort – your link is incomplete – 404
Sorry, will type it in and see if it works:
http://online.wsj.com/article/SB10001424052970204226204576602524023932438.html
The title of the article is:
“How North Dakota Became Saudi Arabia
Harold Hamm, discoverer of the Bakken fields of the northern Great Plains, on America’s oil future and why OPEC’s days are numbered.”
Thanks for allowing the OT post. I believe it is important to know how the two Nobel Prize winners are concocting our energy policy.
Willis
You have reminded me of this great article/tutorial from John Daly, May 10, 2000.
http://www.john-daly.com/ges/surftmp/surftemp.htm
A great treatment of instrument site maintenance with regard to vegetation creep affecting site temperature records.
Bill Illis says:
“The difference is the lower Albedo of the Earth’s surface since it was primarily low-Albedo forests in this period and the only high-Albedo ice in the period was in Antarctica which was probably only a third glaciated at this point (sea ice in the winter of course).”
Actually this is only true for the early Miocene. Antarctica became completely glaciated about 14 nillion years ago in the Middle Miocene, and everything points to that at least East Antarctica has never been deglaciated since. West Antarctica has probably been partially deglaciated at times (last probably during MIS 31 about a million years ago), but never to the point of having significant vegetation.
Anthony, here is a link to the GWPF article which I believe was the source of the WSJ piece:
http://www.thegwpf.org/opinion-pros-a-cons/3999-how-north-dakota-became-saudi-arabia.html
Seems I got that backwards, the GWPF article credits the WSJ. Time to pour another cup of coffee.
Don, thanks for the link to Hamm’s interview. Jawdropping!
Doug,
It’s unreal, ain’t it? What about the part where half a dozen oil companies are facing criminal charges for allegedly causing the deaths of 28 nondescript birds. But the wind turbines at Altamont Pass, up the road from me, are killing scores of golden eagles and nothing happens. What surprises me most is how those eagles manage to splatter themselves on turbine blades that are stationary most of the time. Every time I drive through there it pains me to see most of the windmills standing there, nothing more than statues, monuments representing the benefits of government subsidies.
Being “life like” is not a measure of a models usefulness.
Usefullness can only be assessed in the presence of a clearly (quantified) stated and well defended purpose.
For example, if our purpose is designing flights controls for an air to air missile we will want to use a 6DOF model of the missile. Even that model is not life like, but it is good enough for the stated purpose. If we want to understand the dynamics of separation from the air vehicle at high angles of attack ( in a post stall regime ) we will need even more fidelity. However, if we are trying to evaluate a missile effectiveness in combat, we may use a 3DOF model, not very lifelike at all,
but it fits the intended purpose. If we are trying to size a weapons bay, we dont need anything more than the size and weight.
You dont judge the usefullness of a model without first defining and quantifying the purpose for which you need it. That’s been largely neglected in GCM development. Judging them with unquantified criteria is just as suspect as building them without these criteria to begin with
If the earth’s surface was arid with no vegetation, I think the climate would be hotter, not colder. Thus albedo is not the whole story. In the early phanerozoic, the spread of plants on land was associated with a big fall, not rise, in global temperatures – and this was good for multicellular life in general. The spread of plants, their transpiration of water and making of soil, caused much more water to be retained on land, propelled the hydrological cycle and thus cooled, not warmed, the planet.
There is a reason why the word arid is associated with dry and hot. It is that arid environments are dry and hot. The overall planetary effect of plants is cooling, and it is via the remarkable compound water with its extraordinary heat capacity.
The paper reviewed by Willis snatches at plant albedo as a reason for a warm planet depite low CO2. But plant transpiration makes cloud which, as we now know from recent discussions here at WUWT, dominates planetary albedo and outgoing radiation.
Nice try but try again.
Willis:
As always, your reports are provocative and worth reading — and thinking about.
Your comment that “Me, I think that climate sensitivity is an illusion based on a misunderstanding of how climate works” reminds me of Roger Pielke Sr.’s work along those lines — for example,
http://pielkeclimatesci.wordpress.com/2011/09/19/new-paper-land-useland-cover-changes-and-climate-modeling-analysis-and-observational-evidence-by-pielke-sr-et-al-2011/
Pielke has written on numerous occasions that he thinks that land use/land cover changes are at least as important as CO2 emissions in driving climate change. One of these days, I need to read Pielke’s stuff on this carefully.
Best regards,
Pete Tillman
FWIW, Miocene marine fossil assembleges from Maryland’s Calvert Cliffs seem consistent with a slightly warmer climate than today. e.g. crocodiles.
John Day says:
October 1, 2011 at 4:23 am
Mid-afternoon. Fascinating about the CAM photosynthesis. This would account for part of the reason that the plant was so hot.
w.
ted says:
October 1, 2011 at 8:03 am
You haven’t thought this all the way through. Although there is more temperature change when you include the water vapor, there is also more forcing change … so the ratio of the two (climate sensitivity) changes very little. So whether you calculate using just the albedo figures, just the water vapor figures, or the combination of both, the answers are all very close to the figure I quoted.
w.
Um, Willis, in the framework of the very study you’re invoking, you’re mixing up forcing and feedback.
Scarlet Pumpernickel says:
October 1, 2011 at 6:33 am (Edit)
Scarlet, my thanks, always more to learn. Upon investigation, the plant at my house looks the most like the Aloe succotrina of any of the aloes I’ve seen pictured.
w.
Ted says: [entire unedited post follows]
October 1, 2011 at 7:59 pm
Um, Ted, could you please be a little bit more vague?
w.
Earlier I said “They say half is the albedo change and half is the water vapor feedback. This means that the sensitivity including feedback is 2.3 degrees per doubling, not 1.15. I don’t know what Willis is talking about.”
This is exactly what Ted said at about the same time. I understand exactly what Ted is talking about.
There is a reason why the word arid is associated with dry and hot. It is that arid environments are dry and hot.
It’s a misconception that arid places are hot.
At the same lattitude a humid place will be hotter than an arid place over a year.
A while back, I compared annual average temperatures for places that reported the highest temperatures ever recorded (all in deserts) with humid tropical locations.
In all cases the humid locations had annual average temperatures at least 3C higher than the arid locations.