The Climate Change Hoax

[LesPalenik]

Increase of CO2 is not very desirable, but there are much worse things happening right now.

For example, here in Canada we use in the winter a lot of road salt, and many home owners use also salt on on their driveways. Inevitably, the salt ends up in the lakes.
Lake Simcoe, slightly larger than Lake Mead or Lake Powell, just over an hour north of Toronto is the largest inland lake in southern Ontario and it shows an alarming salt acummulation.  In an average winter, an estimated 90,000 tonnes of salt is applied in the Lake Simcoe watershed. Consequently, in 40 years of monitoring quality of the water, the salt content has increased 5 times.


 

[Ray]

What in the world is a site called, "Luminous Landscape" debating climate change for?

One reason could be, in order to establish that mankind's emissions of CO2 are partly responsible for the great attraction of landscape photography, for some of us, because the additional CO2 helps green our planet and make the average scene more luscious and luminous. This section of the forum is also the Coffee Corner. Got it? 

[Ray]

So we're arrogant if we want to control...pollution? Or population? Or the extermination of entire species? Or is that somehow different in your mind vs controlling the amount of heat and other gases released into the atmosphere?

It did occur to me that someone would misinterpret that statement after I posted it, and it looks as though I was right.
The context is global warming, so my phrase 'arrogant control' refers to control over the global climate, or mother nature.

Controlling pollution is not arrogant but is sensible and wise because we know how to do it (technically) and we understand clearly that pollution affects our health because we can observe its effects in real time.  There is no uncertainty about the adverse effects of pollution.

[Ray]

This one's for Ray:  https://www.nytimes.com/2017/04/05/science/carbon-dioxide-plant-growth-antarctic-ice.html  interesting article on CO2 and increased plant growth .   This shows that I'm open minded on the topic.

Thanks for posting the link, Alan. For some, the article should have more authority because the scientists involved in the study appear to accept that increasing CO2 levels do have some effect on warming the planet. They're not so-called deniers.

However, the article does end on a note of alarm.

"More carbon dioxide might (I'd write does) spur even more growth. But many climate models project that plants will suffer as temperatures rise and rainfall patterns shift. Despite the extra carbon dioxide, worldwide plant growth may fall, and plants will no longer help to buffer the impact of global warming. (I'd mention that climate models are notoriously unreliable.)

“I’ve been referring to this as a carbon bubble,” Dr. Campbell said. “You see ecosystems storing more carbon for the next 50 years, but at some point you hit a breaking point.”

[Bart_van_der_Wolf]

That's what Ray's been saying in his posts here.  That CO2 makes for greater plant growth.  I didn't know of that but assumed just from a logical standpoint that as the earth warms, more cold areas getting warmer will be able to support trees, grass, and all the animals and plants and insects that can expand on to those areas which are relatively barren now because the climate was cold there.

Hi Alan,

When viewed in isolation, or in a controlled environment (like a greenhouse), it's been known for a long time that CO2 has a positive effect on the development of biomass in most/many plants/weeds. That's why purpose built greenhouses use CO2 generators, but they also have full control over moisture/precipitation, nutrients, weeds, and usually a decent level of control over pests.

Unfortunately, outside of a controlled environment such as a greenhouse, the situation gets complicated pretty fast. For one, humans live outside greenhouses. Increased levels of CO2 have an adverse effect on many of our brain functions, especially those that have to do with decision making and learning. Fortunately, we do not immediately die from asphyxiation (CO2 displaces Oxygen in our blood) because that would take much higher levels than found on average in the atmosphere. But we are affected by those negative effects when we do not ventilate enough indoors, so a doubling or tripling of current outdoor levels already affects us (especially those with respiratory or cardiac conditions).

But the situation is more complex still. Besides the question whether more foliage also leads to more nutricious food (assuming nutrients are available in the soil, without the need to use more fertilizer that will also spill in runoffs), it also affects the watermanagement. Because CO2 boosted plantgrowth uses water more efficiently, there will be more soil erosion during rainfall. That runoff has detrimental effects on water quality and for river/lake/marine life.

Also, because less water is being evaporated by the CO2 boosted foliage, atmospheric temperature will increase (evaporation requires/extracts heat). Studies mention effects in the order of up to 40% higher plant temperature, depending on plant species. Add that to the greenhouse effect that CO2 already has on the temperature, and we will see already elevated levels increasing further. And because something like 30-40% of the CO2 in the atmosphere is absorbed by the oceans, ocean acidification will increase as well, which will negatively affect sealife (a huge food source for the future).

You see, a chainreaction of effects (and I've only mentioned a couple of them) is to be expected when humans artificially add significant amounts of CO2 to the natural fluctuations by burning of fossil fuel.

Besides, a simpleton's reaction that loss of permafrost soil will increase agricultural opportunities (while disregarding the release of methane, which is an even worse greenhouse gas, and e.g. fungus/viral release) totally disregards the suitability of such grounds for growing food. Nutrients, accessibility (soggy ground, mountain slopes), light levels at those Latitudes, etc. all play a role.

Scientists are rather unanimous in their assessment, reduction of anthropogenic CO2 levels is required, and it has to be implemented soon. First a reduction of growing amounts from fossil fuel burning is needed, then a reduction of absolute levels can be considered based on improved insight. Prediction models also improve all the time, but we need to act before irreversible effects set in, as they are doing right now.

Things like coral bleaching are a sign, a thermometer of sorts, especially when the coral doesn't get a chance to recover (which can take one or more decades) like they are now hit by raised water temperatures year after year, without chance of recovery. The irreversible loss of land-ice and the inability to regrow seasonal sea-ice is another source of concern, since lots of human/animal life is concentrated around seashores or rivers. Besides flooding, access to drinkable (or usable for irrigation) water is another concern with rising water levels, and if we need to increase desalination projects (which can require a lot of additional power) due to rising sea levels.

Cheers,
Bart

[Alan Klein]

Hi Alan,

When viewed in isolation, or in a controlled environment (like a greenhouse), it's been known for a long time that CO2 has a positive effect on the development of biomass in most/many plants/weeds. That's why purpose built greenhouses use CO2 generators, but they also have full control over moisture/precipitation, nutrients, weeds, and usually a decent level of control over pests.

Unfortunately, outside of a controlled environment such as a greenhouse, the situation gets complicated pretty fast. For one, humans live outside greenhouses. Increased levels of CO2 have an adverse effect on many of our brain functions, especially those that have to do with decision making and learning. Fortunately, we do not immediately die from asphyxiation (CO2 displaces Oxygen in our blood) because that would take much higher levels than found on average in the atmosphere. But we are affected by those negative effects when we do not ventilate enough indoors, so a doubling or tripling of current outdoor levels already affects us (especially those with respiratory or cardiac conditions).

But the situation is more complex still. Besides the question whether more foliage also leads to more nutricious food (assuming nutrients are available in the soil, without the need to use more fertilizer that will also spill in runoffs), it also affects the watermanagement. Because CO2 boosted plantgrowth uses water more efficiently, there will be more soil erosion during rainfall. That runoff has detrimental effects on water quality and for river/lake/marine life.

Also, because less water is being evaporated by the CO2 boosted foliage, atmospheric temperature will increase (evaporation requires/extracts heat). Studies mention effects in the order of up to 40% higher plant temperature, depending on plant species. Add that to the greenhouse effect that CO2 already has on the temperature, and we will see already elevated levels increasing further. And because something like 30-40% of the CO2 in the atmosphere is absorbed by the oceans, ocean acidification will increase as well, which will negatively affect sealife (a huge food source for the future).

You see, a chainreaction of effects (and I've only mentioned a couple of them) is to be expected when humans artificially add significant amounts of CO2 to the natural fluctuations by burning of fossil fuel.

Besides, a simpleton's reaction that loss of permafrost soil will increase agricultural opportunities (while disregarding the release of methane, which is an even worse greenhouse gas, and e.g. fungus/viral release) totally disregards the suitability of such grounds for growing food. Nutrients, accessibility (soggy ground, mountain slopes), light levels at those Latitudes, etc. all play a role.

Scientists are rather unanimous in their assessment, reduction of anthropogenic CO2 levels is required, and it has to be implemented soon. First a reduction of growing amounts from fossil fuel burning is needed, then a reduction of absolute levels can be considered based on improved insight. Prediction models also improve all the time, but we need to act before irreversible effects set in, as they are doing right now.

Things like coral bleaching are a sign, a thermometer of sorts, especially when the coral doesn't get a chance to recover (which can take one or more decades) like they are now hit by raised water temperatures year after year, without chance of recovery. The irreversible loss of land-ice and the inability to regrow seasonal sea-ice is another source of concern, since lots of human/animal life is concentrated around seashores or rivers. Besides flooding, access to drinkable (or usable for irrigation) water is another concern with rising water levels, and if we need to increase desalination projects (which can require a lot of additional power) due to rising sea levels.

Cheers,
Bart

You're assuming that the current climate is the optimum condition from throughout history for "best" situation for all of nature.    Wouldn't that be just an amazing coincidence?  That the climate from let's say around 1880 was the "best" in the history of the earth or at least man,  and we should do everything to maintain that exact climate condition.   

You're only pointing out what seems like negatives due to changes in climate, and many of them will be.  But there are also positives, many of which we haven't even thought of yet.  But the main point is we may find that a temperature rise may be just different from what we've been accustomed too, neither better or worse.  And man, animals, and all of nature will adjust just like they have been for millennia. 

[DeanChriss]

You're assuming that the current climate is the optimum condition from throughout history for "best" situation for all of nature.    Wouldn't that be just an amazing coincidence?  That the climate from let's say around 1880 was the "best" in the history of the earth or at least man,  and we should do everything to maintain that exact climate condition.   

You're only pointing out what seems like negatives due to changes in climate, and many of them will be.  But there are also positives, many of which we haven't even thought of yet.  But the main point is we may find that a temperature rise may be just different from what we've been accustomed too, neither better or worse.  And man, animals, and all of nature will adjust just like they have been for millennia.

Let's say you're right, and as land large areas in places like Africa become incapable of growing food, other places become green. I guess that means you're willing to help the hundreds of millions of displaced people move, and I'm sure the US will be willing to take in maybe 10% of the climate refugees as our fair share, which should amount to at least 10-20 million people.

The WHO says that "Between 2030 and 2050, climate change is expected to cause approximately 250 000 additional deaths per year, from malnutrition, malaria, diarrhoea and heat stress." and "The direct damage costs to health (i.e. excluding costs in health-determining sectors such as agriculture and water and sanitation), is estimated to be between US$ 2-4 billion/year by 2030. I guess you'd say that's "just different from what we've been accustomed too, neither better or worse. As long as it doesn't affect you, I guess.

[Bart_van_der_Wolf]

You're assuming that the current climate is the optimum condition from throughout history for "best" situation for all of nature.

Not necessarily, but what is sure is that we've disrupted the gradual equilibrium by pumping huge amounts of additional grenhouse gasses in the atmosphere since the start of the industrial revolution.

Wouldn't that be just an amazing coincidence?  That the climate from let's say around 1880 was the "best" in the history of the earth or at least man,  and we should do everything to maintain that exact climate condition.

What we do know is that human influence made matter worse. Deforestation, greenhouse gasses and other pollution in the form of Mercury, and Sulphur, and Volatile Organic compounds, and man-made erosion (just look at the land/mudslides where people have chopped away vegetation), the destruction of pollinating bee populations, and plastic-soup in the oceans, and ..., etc.

You're only pointing out what seems like negatives due to changes in climate, and many of them will be.  But there are also positives, many of which we haven't even thought of yet

There are preciously few upsides, and only too many downsides to keep on ignoring it. And closing one's eyes, e.g. by defunding research, is one of the most stupid things to do, with so little time left to remedy the situation for ourselves and the future generation(s).

But the main point is we may find that a temperature rise may be just different from what we've been accustomed too, neither better or worse.  And man, animals, and all of nature will adjust just like they have been for millennia.

We only have to look at how nature is responding. One thing is sure, the change is too fast for evolution to adapt to it. Another thing is also sure, and that is that we are artificially changing the course of events, and not for the better. The scientific community is pretty clear about that. Sure, the models are not perfect, but that's mostly because there are too many inputs that are being changed at the same time, not because the models are bad. Where possible, the isolated study of inputs gives uniform and predictable outputs.

As an example, it is harder to predict the mileage one gets out of one tank of car-fuel, if average speed, outside temperature and winddirection/speed are disregarded. But one thing is sure, leaving the handbreak on during the ride doesn't help fuel efficiency.

Our main handbreak is CO2 emissions, they do not help (outside a greenhouse).

Cheers,
Bart.

[Alan Klein]

I don't know anything about CO2.  That's Ray's expertise.

[Ray]

But the situation is more complex still. Besides the question whether more foliage also leads to more nutricious food (assuming nutrients are available in the soil, without the need to use more fertilizer that will also spill in runoffs), it also affects the watermanagement. Because CO2 boosted plantgrowth uses water more efficiently, there will be more soil erosion during rainfall. That runoff has detrimental effects on water quality and for river/lake/marine life.

Not true, Bart. Sounds like complete clap trap to me. Where are you getting your information from, Bart?

The principle is, with the same amount of water and fertilizer, food crops, general foliage and forests, will produce about 30% more biomass as a result of a doubling of CO2 levels. Such plants use the same amount of water to produce increased growth. There's absolutely no reason why there should be increased run-off of water.
If the plants were to use less water without increasing biomass, which is not the case, you might have a point.

With regard to natural forests, increased growth translates to more leaf litter and more mulch on the forest floor which absorbs more water and actually reduces run-off.

Also, because less water is being evaporated by the CO2 boosted foliage, atmospheric temperature will increase (evaporation requires/extracts heat).

Another statement devoid of logic. Whilst it's true that the amount of evaporation per leaf is reduced by increased CO2 levels, because the leaf spores are reduced in size, the increased CO2 levels result in a proportional increase in the number of leaves, so the amount of evaporation is approximately the same.

Studies mention effects in the order of up to 40% higher plant temperature, depending on plant species.

If that's the case, the plants must like the higher temperature, otherwise they would not flourish. A fundamental basic of common sense in farming is that you grow crops that are suited to the climate. Show me the studies.

Add that to the greenhouse effect that CO2 already has on the temperature, and we will see already elevated levels increasing further. And because something like 30-40% of the CO2 in the atmosphere is absorbed by the oceans, ocean acidification will increase as well, which will negatively affect sealife (a huge food source for the future).

Did you miss my post #70, Bart, where I linked to the following scientific study:

https://earthobservatory.nasa.gov/Features/OceanCarbon/

Here ïs a relevant quote:

"If there is one place in the world where you can measure changes in the ocean carbon sink with atmospheric measurements, it is over the Southern Ocean,” says Le Quéré. “It is the place where you have the least contaminated air, so to speak.”
When Le Quéré plugged atmospheric measurements from the Southern Ocean between 1981 and 2004 into her model, she was startled by the result—something far more interesting than the Antarctic Circumpolar Wave. “The Southern Ocean carbon sink has not changed at all in 25 years. That’s unexpected because carbon dioxide is increasing so fast in the atmosphere that you would expect the sink to increase as well,” says Le Quéré. But it hadn’t. Instead, the Southern Ocean held steady, while atmospheric carbon dioxide concentrations climbed. Why?

You see, a chainreaction of effects (and I've only mentioned a couple of them) is to be expected when humans artificially add significant amounts of CO2 to the natural fluctuations by burning of fossil fuel.

Do you claim an increases of 0.012% from 0.028% to 0,04% significant? I've got more faith in Mother Nature than you, Bart. How many times a day do you wash your hands? Every time you touch your Canon camera? 

Besides, a simpleton's reaction that loss of permafrost soil will increase agricultural opportunities (while disregarding the release of methane, which is an even worse greenhouse gas, and e.g. fungus/viral release) totally disregards the suitability of such grounds for growing food. Nutrients, accessibility (soggy ground, mountain slopes), light levels at those Latitudes, etc. all play a role.

Only a simpleton would think we can stop the permafrost melting by reducing our CO2 emissions. The current levels of CO2 are estimated to persist for a thousand years. If the current warming phase really is caused by human CO2 emissions, which I doubt, then we are already locked into it for the next few decades.
If agricultural practices are too difficult in the melting permafrost areas, for those who have become too used to the nanny state mentality, then a sensible approach would be to plant forests, selecting those species of trees and plants that can thrive in excessively cold climates. If such plants receive a 40% increase in temperature as a result of increased CO2 levels, as you previously claimed, then they'll be in good shape.

[Alan Klein]

Let's say you're right, and as land large areas in places like Africa become incapable of growing food, other places become green. I guess that means you're willing to help the hundreds of millions of displaced people move, and I'm sure the US will be willing to take in maybe 10% of the climate refugees as our fair share, which should amount to at least 10-20 million people.

The WHO says that "Between 2030 and 2050, climate change is expected to cause approximately 250 000 additional deaths per year, from malnutrition, malaria, diarrhoea and heat stress." and "The direct damage costs to health (i.e. excluding costs in health-determining sectors such as agriculture and water and sanitation), is estimated to be between US$ 2-4 billion/year by 2030. I guess you'd say that's "just different from what we've been accustomed too, neither better or worse. As long as it doesn't affect you, I guess.

250,000 deaths seems like a made-up number that doesn't include how many more births climate change will create.  The number is too small, about .00005% of the total population of the world, that one feels confident the scientists really could figure it out. 

[Alan Klein]

...What we do know is that human influence made matter worse. Deforestation, greenhouse gasses and other pollution in the form of Mercury, and Sulphur, and Volatile Organic compounds, and man-made erosion (just look at the land/mudslides where people have chopped away vegetation), the destruction of pollinating bee populations, and plastic-soup in the oceans, and ..., etc.
...

You're conflating the issue of pollution with climate change due to fossil fuels.  No one here is suggesting we pollute the environment.  We've added scrubbers to coal burning plants and have switched to cleaner burning gas for much of our electric production.  Deforestation, plastics in the ocean, etc are a separate issue from climate change.

[Ray]

The WHO says that "Between 2030 and 2050, climate change is expected to cause approximately 250 000 additional deaths per year, from malnutrition, malaria, diarrhoea and heat stress." and "The direct damage costs to health (i.e. excluding costs in health-determining sectors such as agriculture and water and sanitation), is estimated to be between US$ 2-4 billion/year by 2030. I guess you'd say that's "just different from what we've been accustomed too, neither better or worse.

Maybe so, but only if we do nothing to help. The problem is a failure to adapt, and a failure of people in general to change their habits which are based on their culture and upbringing, despite the available education and knowledge on the internet which offer a solution.

If a country is short of water, then one of the solutions is to build dams or desalination plants, and/or transport water through pipes from where it's plentiful.

Trying to make the Sahara Desert fertile, for example, by reducing atmospheric CO2 levels is sheer foolishness.

Confusing the issues seems to be a main tactic of the AGW alarmists.

[Bart_van_der_Wolf]

Not true, Bart. Sounds like complete clap trap to me. Where are you getting your information from, Bart?

Here's a link to an older study that stresses the importance of including these evaporation effects in the modelling of climate changes:
http://www.pnas.org/content/107/21/9513.full?sid=af9cc0cd-9a7c-45f7-b664-2b397f3b98e3

I've seen others as well, but you can also look for them yourself. Think of it as a homework assignment to substantiate your clap trap presumption.

Enjoy,
Bart

P.S. Here is a link to the PDF of the same study, it may display elements that a browser could have difficulties with:
http://www.pnas.org/content/107/21/9513.full.pdf

[DeanChriss]

250,000 deaths seems like a made-up number that doesn't include how many more births climate change will create.  The number is too small, about .00005% of the total population of the world, that one feels confident the scientists really could figure it out.

We're talking about the death of 250,000 people per year between 2030 and 2050 (13 years from now) due to climate change in addition to a whole bunch of suffering. How can additional births make that OK? The unnecessary death and suffering of real living people can't be compensated for by having babies. You may think these people don't matter but I'll bet they have a different opinion. And yes, I'm sure the WHO is far less reliable than Breitbart and Fox.

[Alan Klein]

We're talking about the death of 250,000 people per year between 2030 and 2050 (13 years from now) due to climate change in addition to a whole bunch of suffering. How can additional births make that OK? The unnecessary death and suffering of real living people can't be compensated for by having babies. You may think these people don't matter but I'll bet they have a different opinion. And yes, I'm sure the WHO is far less reliable than Breitbart and Fox.

Don't play that guilt trip game with me. What have you done to save those  250,000 people that are suppose to die in 30 years?? Have you shut off your heating system and slept with a couple of extra blankets?  Have you installed solar panels? 

Anyway your comparison is just silly. Do we argue that spending more money to take care of babies to make them healthier while sacrificing old people because there's less money for health care that we're putting all the old people to death? We don't make those kind of comparisons? We try to do the best we can. Here we're  talking about maintaining systems that benefit society on the average.   Just like where we spend health care dollars,  some groups benefit and others are damaged.  Resources are always limited.

[Ray]

Here's a link to an older study that stresses the importance of including these evaporation effects in the modelling of climate changes:
http://www.pnas.org/content/107/21/9513.full?sid=af9cc0cd-9a7c-45f7-b664-2b397f3b98e3

I've seen others as well, but you can also look for them yourself. Think of it as a homework assignment to substantiate your clap trap presumption.

Enjoy,
Bart

P.S. Here is a link to the PDF of the same study, it may display elements that a browser could have difficulties with:
http://www.pnas.org/content/107/21/9513.full.pdf

Thanks for the link, Bart. This is getting curiouser and curiouser. You've linked to a study which is not only based upon computer simulation models, which tend to be unreliable when simulating such complex issues as climate, but the study openly admits that their models do not include the increased growth of the plants, which I suggest is a known factor (with a very high level of confidence).

How weird is that? To quote:

We performed four 100-year simulations using the CLM3.5/CAM3.5 model coupled with a mixed-layer version of the CCSM3 ocean/thermodynamic sea-ice model (refer to the Methods section for detailed descriptions of the model used and simulations performed).

We note that the focus of this study is to investigate climatic response to changes in plant physiology (through reduced opening of plant stomata with increasing CO2) and does not include additional effects from potential changes in leaf area index and vegetation distributions, both of which are fixed in the simulations performed here.

[LesPalenik]

Dodge just introduced a Demon muscle car with a 840-horsepower 6.2-liter supercharged V8.
In order to save weight, and indirectly reduce amount of emitted CO2, Demon comes standard with no passenger seats, with just one driver seat. In this ingenious way, engineers saved 113 pounds in seats. Not having stereo speakers or an amplifier saved another 24 pounds. That's an exemplary contribution in saving the environment.

[Hans Kruse]

Dodge just introduced a Demon muscle car with a 840-horsepower 6.2-liter supercharged V8.
In order to save weight, and indirectly reduce amount of emitted CO2, Demon comes standard with no passenger seats, with just one driver seat. In this ingenious way, engineers saved 113 pounds in seats. Not having stereo speakers or an amplifier saved another 24 pounds. That's an exemplary contribution in saving the environment.

Yes, I agree it is insane

The same was done with a standard Tesla P100DL and 0-60MPH it is even faster than the Demon http://www.roadandtrack.com/motorsports/news/a32307/this-modified-778-hp-tesla-race-car-can-hit-60-mph-in-21-seconds/ I'm nto sure what the quarter mile would be but probably slightly slower than the Demon. A Tesla Model S P100DL with 5 seats runs 2.28 s 0-60MPH and as fast as the Demon https://www.youtube.com/watch?v=wSSdMvl8_mY It's funny to see the Tesla against those muscle cars and beat them on the quarter mile drag strip

[Bart_van_der_Wolf]

Thanks for the link, Bart. This is getting curiouser and curiouser. You've linked to a study which is not only based upon computer simulation models, which tend to be unreliable when simulating such complex issues as climate, but the study openly admits that their models do not include the increased growth of the plants, which I suggest is a known factor (with a very high level of confidence).

How weird is that?

Not that weird, since they did not attempt to create an all-encompassing world climate simulation but rather:
"In this study, we examine the climate effect of CO2 physiological forcing using a coupled global atmosphere-land surface
model".
and
"the focus of this study is to examine the nature of climate response to CO2-physiological forcing in terms of both magnitude and pattern, and contrast it with the effect of CO2-radiative forcing".
and
"This study provides an independent evaluation of the role of CO2-physiological forcing in CO2-induced climate change."

So their goal was to show how significant it is to add "physiological forcing" to improved climate models. And only that factor already influences several other metrics, like the hydrological cycle and cloud coverage (which reduces solar radiation and traps reflective and emissive earth temperature/radiation).

Sure, a next step could be to add models for biomass change, which is more complicated than you seem to be suggesting. More biomass, assuming there are enough nutrients, would also change the soil/vegetation surface and cloud albedo effects, and thus temperatures and resulting winds, which in turn affect transpiration and evaporation effects which this report found to be significant.

Since different plants/trees respond with different amounts of biomass increase (a few react with biomass decrease, and healthy plants grow less than sick plants) in response to elevated levels of CO2, it would only complicate the model or force to use one very specific assumption which could somewhat conflict with another assumption. So it seems prudent to not include it as a variable at all, for the purpose of this study. Also, by using known existing atmosphere/climate models, it allows other scientists to do their own research to either challenge or confirm the conclusions/recommendations of this study.

That's why they also mention: "We note that the focus of this study is to investigate climatic response to changes in plant physiology (through reduced opening of plant stomata with increasing CO2) and does not include additional effects from potential changes in leaf area index and vegetation distributions, both of which are fixed in the simulations performed here."

So that was a deliberate choice for this study, the 'additional effects' were fixed in the simulations (because it was beyond the scope of their study). Not weird at all, it just was not what they were investigating.

Cheers,
Bart

P.S. Under the chapter Discussion, the authors do mention there are some conflicting studies as to the effect when the vegetation dynamics reaches new equilibrium under doubling CO2 concentrations, like a cooling of 0.1 K over land caused by surface cooling from increased leaf area index, but also a land warming of 1.4 K as a result of decreased surface albedo.