CO2 and the correlation with rising atmospheric temperatures

[jochem]

I just read the policy for this forum "Earth" so i hope my next question will be approved, it is with the best intentions.
My friends and i where having a discussion about CO2 and the correlation with the raising temperature, we know that CO2 is a greenhouse gas. About that, CO2 is a greenhouse gas, there is to my knowledge no doubt about that. However is there consensus in the science community over how much influence the raising CO2 has on the temperature and if this is significant? I would understand if my question is to wide ranged. We were just curious!

Thanks in advance
P.S. sorry for my grammar mistakes

 

[.Scott]

I just reviewed the policy on this subject. It's close, but I don't think you've crossed the line ... yet.

Strictly speaking, it is not up to science to come up with a "consensus". Never-the-less, there is often great political practicality in doing so.
I would recommend taking a look at reports from the IPCC: https://www.ipcc.ch/

My own assessment is that the topic of climate change when viewed in terms of public policy is not as clear cut as it needs to be - but there is continuous progress.
Ideally, you would be able to predict both what would would happen if nothing was done and what would happen given a specific proposal - but that is not available. Still, policy decisions are commonly made with less than ideal information - which is necessary. Commonly you simply have to make an educated guess at whether the cost of a program will eventually be worth the expense.

So the real issue is whether science has provided good enough models to support significant (economy-changing) policy decisions. And I think there is still room for debate on that.

The last full assessment by the IPCC was done in 2014. That report is here: https://www.ipcc.ch/site/assets/uploads/2018/02/SYR_AR5_FINAL_full.pdf
They are currently working on an updated version.

 

[Bandersnatch]

@.Scott the question wasn't about policy, but about the impact of CO2 on GW. I don't think there's any debate in the scientific community about its rising concentrations being the sole driver of the recent global temperature increase. My impression was the current work is focused on narrowing down climate sensitivity to further changes in atmospheric CO2.

@jochem I don't think this site is the best choice for making sense of this topic. We just don't have that many experts on the subject frequent these boards, and the forum policy is to some extent a reflection of that. You might get lucky, but more often than not you end up with a lot of essentially lay opinions.

 

[Genava]

However is there consensus in the science community over how much influence the raising CO2 has on the temperature and if this is significant?

Hi,

This question is quite an old one. This subject started with Tyndall and Arrhenius in the 19th century. Guy Callendar will continue their work in 1930s and the theory that CO2 is a major driver of the average global temperature is becoming debated and popularized after WWII. Gilbert Plass in the 1950s published several papers that started to build the consensus around it:
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.2153-3490.1956.tb01206.x
https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/qj.49708235307

Today, we have satellite data supporting that theory:
https://journals.ametsoc.org/doi/10.1175/2008BAMS2634.1

And direct measurement of the greenhouse effect in the atmosphere:
https://www.nature.com/articles/nature14240

If you are looking for an easy way to understand the concepts behind it and to have better arguments in your next debate, I suggest to go on the webpage of American Chemica Society:
https://www.acs.org/content/acs/en/climatescience/climatesciencenarratives.html

I hope it is what you are looking for.

 

[.Scott]

Let's see if I can readdress the OP in light of the comments by @Bandersnatch.

It's somewhat difficult to address the notion of "consensus" because that's not part of the science of climate change.
I can find examples of the basis for a claimed "consensus" on the web - and the arguments are good - but they do not meet the criteria for citing articles on this subject in this forum.

But the key is "climate model" and it is discussed in that link I provided to "AR5".
https://www.ipcc.ch/site/assets/uploads/2018/02/SYR_AR5_FINAL_full.pdf
That document is kind of the "top of the tree", with citations down to another level of IPCC documents, with citations to the actual science papers.
There are important terms on page 26 ("certainty", "likely", "very likely") that are used throughout the document to describe how well the assertions are supported by the research.

I am trying to be apolitical, but I think it is safe to say that there is a consensus among working climate models that the global warming that has been observed over the past three or four decades can be explained by rising CO2 levels alone and cannot be explained without considering those rising CO2 levels. I would not conclude from that that "rising concentrations [are] the sole driver of the recent global temperature increase". In fact, methane and N2O are certainly significant contributors (see figure 1.3 in AR5). I would conclude that rising CO2 is the primary contributor. I would also not discount agricultural water usage and contrails as potential noteworthy contributors.

Here is an article that describes the contrail issue. I am not citing it to support a claim that it is right - only that it is a "potential noteworthy contributor".
https://globalnews.ca/news/2934513/...ge-for-an-unlikely-climate-change-experiment/

The OP also asked if these temperature changes are significant. This is a very policy-oriented question. Why else would you ask about the significance?
The AR5 document does describe projected consequences of global warming for the coming decades - and I think it does a passable job in defending those projections. But I think the reader needs to be very aware that there is a qualitative difference between a "very likely" estimate of historical trends based on collected data and a "very likely" projection based on a set of models - even though both are identified as "90-100%". Also, these are projections based on a modelling of all anthropogenic factors, not just CO2.

That said, you are more likely to find something that you consider "significant" in AR5 section 2 (projections) than in section 1. For example, the summary at the start of section 2 reads "Surface temperature is projected to rise over the 21st century under all assessed emission scenarios. It is very likely that heat waves will occur more often and last longer, and that extreme precipitation events will become more intense and frequent in many regions. The ocean will continue to warm and acidify, and global mean sea level to rise.".
Section 2.3 gets into "impacts", for example:

Climate change over the 21st century is projected to reduce renewable surface water and groundwater resources in most dry subtropical regions (robust evidence, high agreement), intensifying competition for water among sectors (limited evidence, medium agreement). In presently dry regions, the frequency of droughts will likely increase by the end of the 21st century under RCP8.5 (medium confidence). In contrast, water resources are projected to increase at high latitudes (robust evidence, high agreement). The interaction of increased temperature; increased sediment, nutrient and pollutant loadings from heavy rainfall; increased concentrations of pollutants during droughts; and disruption of treatment facilities during floods will reduce raw water quality and pose risks to drinking water quality (medium evidence, high agreement).

 

[Genava]

Here is an article that describes the contrail issue. I am not citing it to support a claim that it is right - only that it is a "potential noteworthy contributor".
https://globalnews.ca/news/2934513/...ge-for-an-unlikely-climate-change-experiment/

Am I the only one to find this article contradicting itself? Why it jumps on conclusion to choose specifically one side while the others statements suggest either the other side or the uncertainty.

 

[.Scott]

Am I the only one to find this article contradicting itself? Why it jumps on conclusion to choose specifically one side while the others statements suggest either the other side or the uncertainty.

As I said, I am not claiming that it is "right" - only that contrails should not be discounted. The gist of the article is that they can have an effect - potentially warming or cooling. It is part of my argument against the @Bandersnatch assertion that there is consensus that CO2 is the "sole" contributor.

I believe there were studies of the 9/11 climate effect. If anyone can find a good one, that would be great. I could not - but I don't have the scholastic resources that many others have on this forum.

That article does cite 5 other sources. The good ones are:
http://www.atmos.washington.edu/~rennert/etc/courses/pcc587/ref/Travis-etal2002_Nature.pdf (a NOAA article with good citations)
https://www.nasa.gov/home/hqnews/2004/apr/HQ_04140_clouds_climate.html

There are also indirect references (but no citations) to other articles more specific to the 9/11 effect.

 

[Bandersnatch]

I said the sole driver, of the current temperature rise.

 

[.Scott]

I said the sole driver, of the current temperature rise.

If that's different from "sole contributor", then I don't think there are enough people with an opinion about it to constitute a "consensus".
But, I'll bite anyway: What is a "sole driver"?

 

[russ_watters]

I just read the policy for this forum "Earth" so i hope my next question will be approved, it is with the best intentions.

Tone via "best intentions" matters a lot here. This thread opening is fine, and welcome to PF.

My friends and i where having a discussion about CO2 and the correlation with the raising temperature, we know that CO2 is a greenhouse gas. About that, CO2 is a greenhouse gas, there is to my knowledge no doubt about that. However is there consensus in the science community over how much influence the raising CO2 has on the temperature and if this is significant?

This isn't a complete and difinitive answer to your question, but a partial lab and consensus answer:
https://en.wikipedia.org/wiki/Global_warming_potential
https://www.epa.gov/ghgemissions/understanding-global-warming-potentials

Global Warming Potential is a quantitative/lab measurement/calculation of how much potential a certain gas has to affect global warming:

The GWP depends on the following factors:

• the absorption of infrared radiation by a given species
• the spectral location of its absorbing wavelengths
• the atmospheric lifetime of the species

The factors themselves are objective, but the weighting/scoring of these measurements can be debated. What isn't clear to me is how exactly the formula was arrived at, meaning to what extent the scoring represents a scientific consensus (by what scientists?) versus a political consensus.

[edit]
I realize on rereading I may have misinterpreted this post. When I saw "...how much influence the raising CO2 has..." I autocompleted "...vs other gases..." which may not have been intended. Maybe you intended vs other non-greenhouse gas factors such as solar output, random noise, etc. So maybe you'll find this informative, though maybe not quite relevant. I'll leave it be and let you decide if you want to pursue my angle.

 

[russ_watters]

@.Scott the question wasn't about policy, but about the impact of CO2 on GW. I don't think there's any debate in the scientific community about its rising concentrations being the sole driver of the recent global temperature increase. My impression was the current work is focused on narrowing down climate sensitivity to further changes in atmospheric CO2.

I agree with your take on the OP, but the "sole driver" bit is way too strong. There are many climate drivers and more to the point, CO2 is not the only greenhouse gas humans are emitting large quantities of. In the media and politics, the issue is often simplified to be strictly about CO2, but it isn't. Off the top of my head and a quick google, human-caused methane release is 28% - more than a quarter - of the human caused global warming. This may not strictly be a required part of this thread, but in terms of policy it is critically important to decision making that by current measures, livestock methane (a part of that 28%) contributes more to global warming than all forms of transportation CO2 output combined.
https://www.skepticalscience.com/methane-and-global-warming.htm

This is the reason the GWP measure I referred to in my previous post exists.

@jochem I don't think this site is the best choice for making sense of this topic. We just don't have that many experts on the subject frequent these boards, and the forum policy is to some extent a reflection of that. You might get lucky, but more often than not you end up with a lot of essentially lay opinions.

This is true, but one thing we do have is quality standards that keep discussions on point and high quality. So while our best on this subject may not be as good as other subjects, it may still be better than other forums.

 

[russ_watters]

The OP also asked if these temperature changes are significant. This is a very policy-oriented question. Why else would you ask about the significance?

There are two potential uses of the word "significant" here. One is significant from a standpoint of whether it affects us enough that we should put effort into dealing with it. That's what you're referencing.

The other is "significant" from a statistical standpoint. E.G., is the 10 or 100 year change in average temperature larger - more "significant" - than the annual change? (10, no; 100, projected yes). Larger or faster than the millennial change? (faster, yes). The word is a bit of a value judgement, so (per a theme today...) we have to attach a scale to it to measure against. My read is this is what the OP was asking.

There is some overlap I suppose. One of the problems with acceptance has been the "significance" - the signal to noise ratio - of the data. When annual fluctuations are close to or larger than the long term measured trend, it is easy to speculate that the low signal to noise ratio makes the trend an anomaly. 10 or 20 years ago this may have been a valid concern -- or at least for a layperson like me tougher to pull the signal out of the noise than for an expert. Today, it's not.

 

[PeterDonis]

There are many climate drivers and more to the point, CO2 is not the only greenhouse gas humans are emitting large quantities of.

Not only that, but not all climate drivers are greenhouse gases. Another obvious one that humans have had a significant effect on is land use.

 

[Bandersnatch]

@.Scott, et al
Reading it again in the morning, I agree it was a poorly worded statement that paints a picture that is too black and white. I don't want to be defending it too vigorously, and anyway it looks like we're all on the same page.
What I wanted to convey, is that while there are other contributors to climate change, they're either feedbacks (e.g. water vapour concentration, ice-related albedo changes), outright negative forcings (solar), or not comparable in magnitude to CO2 emissions (other greenhouse gases). Much like one could pin the driving influence to solar forcing at the end of glaciations, with other contributors acting as amplifying feedback.

But then again, that's still too black and white (aren't methane emissions comparable, really?).

 

[Genava]

The gist of the article is that they can have an effect - potentially warming or cooling. It is part of my argument against the @Bandersnatch assertion that there is consensus that CO2 is the "sole" contributor.

I have no problem with the assertion that they have an effect. I am only surprised with the cherry-picking of the quote from Patrick Minnis where the entire sentence has been cut, resulting in a misleading assertion. Moreover, he didn't precise that the quote is incomplete and he add a baseline dot in the quote to suggest it is the entire sentence. It is something forbidden for us academicians. I find even more surprising to rely on an old study and an old news to talk about a complicated and currently debated subject. From a quality perspective, this news article from Patrick Cain is bad.

In 2018, there was a review in Nature on the effect of the contrails if you are interested:
https://www.nature.com/articles/s41467-018-04068-0

In 2005, a bit old but there was another review which is in open-access:
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2005GL022580

 

[Astronuc]

Besides CO2, there are other gases that contribute to the warming of the atmosphere, e.g., methane. There does seem to be some different opinions on the relative importance of methane.

https://www.edf.org/climate/methane-other-important-greenhouse-gas
"About 25% of the manmade global warming we're experiencing is caused by methane emissions" and the site indicates that methane is 84 times more potent than CO₂ in the first two decades after its release.

https://www.epa.gov/ghgemissions/overview-greenhouse-gases
A pie chart puts methane at 10% of emissions, but indicates "Pound for pound, the comparative impact of CH₄ is more than 25 times greater than CO₂ over a 100-year period."

So one needs to look at a variety of sources and understand how data are being presented.

As PeterDonis indicated, another factor is land use, e.g., deforestation (or more generally removal of plants) for buildings and agriculture. Building roofs and wall, roadways (asphalt and concrete) absorb light, heat up and emit in the infrared, as opposed to the trees or grass lands they replace. The EPA's site mentions "Carbon dioxide is removed from the atmosphere (or "sequestered") when it is absorbed by plants as part of the biological carbon cycle."

 

[.Scott]

In 2018, there was a review in Nature on the effect of the contrails if you are interested:
https://www.nature.com/articles/s41467-018-04068-0

In 2005, a bit old but there was another review which is in open-access:
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2005GL022580

Thanks.

 

[.Scott]

At this point in the discussion, I think it is becoming easier to see the boundary between science and climate policy.
Science has its customers - and policy-makers are near the top of the list.

If policy-makers are of a mind that they want to keep nature as it has been, then the models that have been created so far will suffice. They generally support the notion that we are changing weather patterns and "messing up" some fauna and flora and that we will be continuing to do so without policy change. In most cases, the studies do not meet the 3 or 5 sigma standard for accepted science, but that is not the criteria. You don't wait to jump out of the way of an oncoming train until you have a 5-sigma study demonstrating that it will hurt you.

On the other hand, those customers that have no interest in preserving the globe except as it impacts the industrialized nations will be less satisfied with the science - because it would be correctly viewed as incomplete. The models, as they are, suggest that there will be some negative impact outside of the tropics - but it clearly may be more cost effective (and economy-preserving) to brace for more storms rather than attempt to prevent them. More importantly, it isn't good enough to say that reducing CO2 emissions will mitigate the issues, they would want to know what portion of the problem belongs to CO2 because the rest of it will remain unaddressed with many CO2 reduction programs.

 

[PeterDonis]

If policy-makers are of a mind that they want to keep nature as it has been, then the models that have been created so far will suffice.

I'm not so sure that's actually true. I'm not sure that either the models or the evidence we have are sufficient to support specific policy interventions with good confidence that they will "keep nature as it has been", i.e., that they will reliably stop further change. I'm even less confident that we have enough predictive ability in economics to reliably say that, even if a particular policy intervention does mitigate what it's supposed to mitigate, that it will do so at a cost that is less than the benefit. Costs have a way of ending up being a lot more than they're predicted to be.

You don't wait to jump out of the way of an oncoming train until you have a 5-sigma study demonstrating that it will hurt you.

Agreed, but you also don't need a complicated argument based on models to tell you that jumping out of the way of the train will, with high confidence, prevent you from getting hurt.

those customers that have no interest in preserving the globe except as it impacts the industrialized nations will be less satisfied with the science - because it would be correctly viewed as incomplete.

I'm not sure that the current apparent fashion of describing this situation as a conflict between developed nations and developing nations is a good idea. As you note, in many cases it might be more cost-effective to adapt to the changes instead of trying to mitigate them; but it's much harder to convince developing nations to do that if they are told that their problems are the developed nations' fault. But that might be getting off topic since it's really a matter of politics, not science.

 

[Genava]

I'm not so sure that's actually true. I'm not sure that either the models or the evidence we have are sufficient to support specific policy interventions with good confidence that they will "keep nature as it has been", i.e., that they will reliably stop further change. I'm even less confident that we have enough predictive ability in economics to reliably say that, even if a particular policy intervention does mitigate what it's supposed to mitigate, that it will do so at a cost that is less than the benefit. Costs have a way of ending up being a lot more than they're predicted to be.

You are comparing climate forecast with economical forecast? Everything related with human behavior is problematic because the causal link is difficult to prove and even difficult to measure. But climate science relies mostly on physics and chemistry. Contrary to most of the economical theories, the greenhouse effect and its role in the current warming do relie on empirical evidences and experiments. Climate forecasts are better and even the old model of James Hansen in the 80s made a good prediction matching the current measurements. If the American Chemical Society, the American Physical Society and The Geological Society of America support the consensus, there are good reasons for this. The same for the NASA, for the military and for insurances. Even Exxon and Shell in their own internal documents were in agreement with this. Moreover, the consensus is built since the 80s and since this time, we have increased the research on the subject by several orders of magnitude. And since this the consensus has been strengthen, not the opposite. No others explanation has been found with a sufficient criteria.

The only part where I agree with you is about the effect of a policy. Clearly, the human science part of our comprehension of the problem is the weakest. But for the physical and chemical parts, the most conclusive and significant theories grounded with the most solid evidences from climate science support the idea that reducing our emissions will reduce greatly the warming trend.

 

[PeterDonis]

You are comparing climate forecast with economical forecast?

No, I'm just saying that predicting the costs of any policy requires economic forecasts, not climate science forecasts. And economic forecasts of costs have a long history of being too low, sometimes by very large amounts.

 

[Bandersnatch]

No, I'm just saying that predicting the costs of any policy requires economic forecasts, not climate science forecasts. And economic forecasts of costs have a long history of being too low, sometimes by very large amounts.

Can't one make the same argument about the costs of adaptation?

 

[PeterDonis]

Can't one make the same argument about the costs of adaptation?

Yes. It applies to estimates of the costs of any policy. The difference with adaptation is not that we can estimate its costs more accurately; it's that adaptation is what people are going to do anyway, since people are always going to be trying to anticipate the future and act accordingly. So adaptation does not require a single coordinated policy response across the entire world; whereas reduction of CO2 emissions does, at least based on the calculations of how much reduction it would take to make a significant difference. (And based on past experience, such a single coordinated policy response is not realistically going to happen.)

 

[Genava]

No, I'm just saying that predicting the costs of any policy requires economic forecasts, not climate science forecasts. And economic forecasts of costs have a long history of being too low, sometimes by very large amounts.

Sorry, I misunderstood your message.

Yes. It applies to estimates of the costs of any policy. The difference with adaptation is not that we can estimate its costs more accurately; it's that adaptation is what people are going to do anyway, since people are always going to be trying to anticipate the future and act accordingly. So adaptation does not require a single coordinated policy response across the entire world; whereas reduction of CO2 emissions does, at least based on the calculations of how much reduction it would take to make a significant difference. (And based on past experience, such a single coordinated policy response is not realistically going to happen.)

You are right, adaptation is mainly done without any intervention. But adaptation can failed as well, it is a talk related to what Jared Diamond wrote in his books. The adaptation of our societies will also depend on the intensity and on the rate of the global change. It's a risky bet to rely on that to get us out of trouble and that opens up a question, how far we can adapt? I have the feeling that +5°C in one century would be something difficult to overcome serenely.

But in the end maybe you will be right and we will rely only on adaptation. Clearly the single coordinated policy is not working at all. All countries are tempted to drag their feet to recover the economic benefits lost by others.

 

[russ_watters]

The difference with adaptation is not that we can estimate its costs more accurately; it's that adaptation is what people are going to do anyway, since people are always going to be trying to anticipate the future and act accordingly. So adaptation does not require a single coordinated policy response across the entire world; whereas reduction of CO2 emissions does, at least based on the calculations of how much reduction it would take to make a significant difference.

Let me twist that a bit: adaptation is what people are going to do any, without anticipation. Switching to non-carbon energy and adapting in advance to rising sea levels (among other things) are the same type of anticipatory/predictive adaptation. But humans are in fact not good at predictive adaptation, we tend to adapt only when forced to react. And often we have to get dragged into adaptation long after it is clear we should have.

I drove past a house on the beach in the Outer Banks last summer which had its support pilings underwater at high tide. It was occupied.

The main point though, that I agree with you on, is that adaptation is often done without intentional intervention. It basically happens on its own.

You are right, adaptation is mainly done without any intervention. But adaptation can failed as well, it is a talk related to what Jared Diamond wrote in his books. The adaptation of our societies will also depend on the intensity and on the rate of the global change. It's a risky bet to rely on that to get us out of trouble and that opens up a question, how far we can adapt?

Well, that requires defining "failure". Darwin would probably say that failure is when a species goes extinct. Humans are not going to go extinct due to global warming. I live 100 miles from the ocean and 300 feet above sea level and I have air conditioning. I'm going to be just fine. People living in Bangladesh? Probably not. If 10 million Bangladeshis die and their economy collapses due to massive annual flooding, but the worst that happens to me is I lose $500,000 in equity in my beach house* because the federal government decides it doesn't want to continue paying me to rebuild it it when it collapses every 10 years, is that a "failure"?

[I don't own a beach house, it's just an example consequence.]

 

[PeterDonis]

often we have to get dragged into adaptation long after it is clear we should have.

Fair point. Misaligned incentives don't help either: I believe the US government has a program that basically rebuilds your beach house if it is damaged or destroyed by certain weather events like hurricanes or flooding. I wouldn't be surprised if that beach house you saw in the Outer Banks would be covered. Why anticipate on your own when someone else will have to bear the consequences?

 

[russ_watters]

Misaligned incentives don't help either: I believe the US government has a program that basically rebuilds your beach house if it is damaged or destroyed by certain weather events like hurricanes or flooding. I wouldn't be surprised if that beach house you saw in the Outer Banks would be covered. Why anticipate on your own when someone else will have to bear the consequences?

Yes, that is what I was referring to:
https://en.wikipedia.org/wiki/National_Flood_Insurance_Program
https://www.nytimes.com/2017/11/04/business/a-broke-and-broken-flood-insurance-program.html

A nugget from the second link:

It has spent billions of dollars repairing houses that just flood again. Its records, for instance, show that a house in Spring, Tex., has been repaired 19 times, for a total of $912,732 — even though it is worth only $42,024.

Ouch.

I know this thread wasn't initially intended to be a policy debate, but this is the type of program that is nonsensical with or without - but especially with - climate change bearing down on us.

 

[.Scott]

Yes, that is what I was referring to:
https://en.wikipedia.org/wiki/National_Flood_Insurance_Program
https://www.nytimes.com/2017/11/04/business/a-broke-and-broken-flood-insurance-program.html

A nugget from the second link:

It has spent billions of dollars repairing houses that just flood again. Its records, for instance, show that a house in Spring, Tex., has been repaired 19 times, for a total of $912,732 — even though it is worth only $42,024.

In case you were thinking that this was a seacoast community:
Spring, TX is north of Houston. It has an elevation of about 120 feet ASL.
It is unclear whether climate change would help or hurt them.

Even without a sea level rise, homes (along with the land they sit on) are lost near the seacoast. Plum Island in Massachusetts is a good example of this. Since I began visiting the island as a child, the northern tip - along with many homes and a Coast Guard Station, have been lost.

 

[Genava]

Well, that requires defining "failure". Darwin would probably say that failure is when a species goes extinct. Humans are not going to go extinct due to global warming.

I'm always careful when it comes to bringing a Darwinian analysis to a social issue, for historical and ethical reasons But I agree, nothing suggests that humanity will go extinct. Civilization collapsus or regression, is a possibility but not extinction.

If 10 million Bangladeshis die and their economy collapses due to massive annual flooding, but the worst that happens to me is I lose $500,000 in equity in my beach house* because the federal government decides it doesn't want to continue paying me to rebuild it it when it collapses every 10 years, is that a "failure"?

It is a common bias among human beings to think that bad things will happen only to others. Moreover, human fear-reaction cannot understand correctly systematic risk and vulnerability. Climate is one of the main drivers of all of processes occurring on the Earth's surface, it is maybe wrong to underestimate its impact on our economy and our societies. In my country, Switzerland, we are in majority conservatives but since our environment is very sensitive to climate change (the rate of warming is twice than the world's), we are motivated to do something. Even if we are among the "richest" humans on Earth, we won't duck the negative effects.

 

[gmax137]

Yes, that is what I was referring to:
https://en.wikipedia.org/wiki/National_Flood_Insurance_Program

That wiki is very interesting, thanks!

 

[.Scott]

Hello @Charlie Cheap:
The role of greenhouse gases and the lead role of CO2 in the warming we have seen over the past 50 years is well established and described in the first section of the IPCC report I cited earlier:
https://www.ipcc.ch/site/assets/uploads/2018/02/SYR_AR5_FINAL_full.pdf
The gas that contributes the most to the greenhouse effect is water vapor. But changes in water vapor occur over days - so there is no long-term cumulative effect. CO2, the number two contributor to the affect, on the other hand, can last many years. So CO2 can accumulate and produce long lasting changes.
Other contributors to the green house effect are N2O, methane, and cloud cover.

We now have a satellite up there (OCO-2) that can measure CO2 concentrations. Here's what it looks like:

Notice a few things here:
1) The range is 387-402.5. Not very wide. It's that base number (387 ppm) that is continuing to rise.
2) The areas of highest concentration is not the Pacific ring (volcanoes). But it does include all major industrial areas.
3) There definitely seem to be other sources - so I wouldn't let those cows off the hook right away.
4) This is from 2014, when OCO-2 was first operational. Those large CO2 generators in the southern hemisphere are not there every year.

That graphic comes from an article which also includes a chlorophyll map (from that same satellite).
Here is a link: http://www.climatecentral.org/news/nasa-satellite-most-detailed-view-co2-18459

For more clues about those areas in Africa and South America that seem to be such large contributors, see this article:
https://www.nasa.gov/press-release/...of-earth-s-recent-record-carbon-dioxide-spike

 

[Buzz Bloom]

What I wanted to convey, is that while there are other contributors to climate change, they're either feedbacks (e.g. water vapour concentration, ice-related albedo changes), outright negative forcings (solar), or not comparable in magnitude to CO2 emissions (other greenhouse gases).

Hi Bandersnatch:

I think you are forgetting a period of approximately 10-20 years near the end of the 20th century. This was a period in which the largest changes in average annual temperature increases occurred since about 1950 (when human releases of CO2 became the dominant factor), and these increases were primarily the result of fluorocarbons emitted which destroyed a lot of ozone before international policy (almost entirely) ended this practice. I do not have the time now to post references, but I will try to add some later today.

The reason ozone reduction was so significant, although its fraction of human gases released were quite small, is the average of each photon of UV radiation reaching the Earth was much much greater than that of the average energy of the green house gas photons.

ADDED
The following cites a 2010 article: "Twenty Questions and answers about the ozone Layer: 2010 update".

https://acd-ext.gsfc.nasa.gov/Documents/O3_Assessments/Docs/WMO_2010/Q2_QA.pdf​

Q18 (pp 55-59) and Q19 (pp 60-63) are about effects of warming. Page Q.61 has four charts. The bottom right chart shows the changes in UV radiative forcing of climate between 1960 extrapolated to 2020. In 1960 the forcing value was 0.02 watts per square meter (WPSM) It peaks at about 0.35 WPSM about 1995. Since 1995 it has declined slowly to about 0.32 WPSM.

This should be compared with the increase in average world temperature - the hockey-stick effect.

I remember reading some other articles but I am having trouble now finding them again. I will do some more searching tomorrow.

Regards,
Buzz

 

[Genava]

.Scott, my real problem with so-called science on climate change is the reference to "consensus" among scientists. Science is the ability to perform a repeatable test in order to prove or disprove something. Supposedly, science is set-in-stone once the studies/tests are complete, and no guess-work is involved once that work is done.

Maybe you should try to apply the idea of a consensus on a different subject, less political. It is true that there is no absolute certitude in science, but I am sure you see everyday that our policy, our economy and our public funds rely on scientific principles and subsidize some organizations for these reasons. And we need to rely on these scientific principles and to consider them as truths to live. Like for example geological exploration and resources mining which rely a lot on plate-tectonics (which is a more recent theory than human induced climate change). Surprisingly there have been contrarians on this theory, like Arthur A. Meyerhoff until his death in the 1990s. But having some contrarians does not mean that the we should refuse the principle of a consensus or that we should refuse to rely on these scientific principles for our economy.

What I want to highlight with my analogy is that we accept all the time most of the consensus from the scientific community and it is a good thing. The problem with the acceptance of climate science does not come from a problem in science but in politics.

 

[.Scott]

@Charlie Cheap
Strictly speaking, the physical sciences don't "prove" things. The results from scientific experiments can support of refute one or more scientific hypothesis. With enough data collected, the likelihood of a misinterpretation can become very low - this is expressed as a standard deviation (sigma confidence) value.

For example, CERN does not declare a new particle until is has accumulated evidence to reach the five sigma level. This is far from "proof". We should expect that should 1 of every 3.5 million of these announcements are mistakes. So if anyone "sets them in stone", they should expect to have to break one stone out of every 3.5 million.

A lot of the climate change measurements, experiments, and projections do not come close to five sigma confidence. In the IPCC AR5 report, confidence is expressed in these terms:

The likelihood, or probability, of some well-defined outcome having occurred or occurring in the future can be described quantitatively through the following terms: virtually certain, 99–100% probability; extremely likely, 95–100%; very likely, 90–100%; likely, 66–100%; more likely than not, >50–100%; about as likely as not, 33–66%; unlikely, 0–33%; very unlikely, 0–10%; extremely unlikely, 0–5%; and exceptionally unlikely, 0–1%.

So even "virtually certain" means that you would have to break as many as one stone in 100.

This is why I have said that science is not about "consensus". It is about experiments and measurements; assessing how confident one can be based on the results of those experiments; and looking for new ways to explain the results of the experiments.
There's a lot of stuff that is "set in stone", like how much infrared CO2 absorbs. That's the kind of experiment or measurement that can be repeated over and over - with confidence far, far exceeding 5 sigma. Or this:

Anthropogenic greenhouse gas emissions have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever. This has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century.

That "extremely like" puts it at 99+% at least 2.5 sigma. But the only "consensus you can expect is that it is "very like" as defined in the report, not that it is "true".

Here's another statement from the IPCC:

It is likely that the frequency of heat waves has increased in large parts of Europe, Asia and Australia.

So there is as much as a 10% change that those heat waves are just a coincidence - unrelated to global warming. But it's still a scientifically-based statement and it is also potentially useful information to policy-makers.From US Energy Information Administration:

Here US household gasoline consumption (from https://www.eia.gov/todayinenergy/detail.php?id=33232)

But the number of households has increased and the products we use need oil during manufacturing and shipping, so...
Here is US total energy consumption (from https://www.eia.gov/todayinenergy/detail.php?id=9210)

I don't think that this supports your statement that the US has "dropped its [C]O2 levels dramatically over the past 4 decades". Perhaps we've trimmed them.
But the affects of CO2 are cumulative, so even if we stay at this level of CO2 output, things will continue to warm up.And have fun with those cars!

 

[.Scott]

@Charlie Cheap :
You listed a litany of ideas that were popularly considered "scientific" and were not correct. That's the type of history that motivates scientists to strictly stick to the scientific method.

In science, the facts are the experiments and the experimental results. Fortunately, that seems to be what you are asking for.

The chart below shows three sets of measurements (black, blue, and tan) for global temperatures. The chart is adjusted so that zero is the average planetary temperature from 1986 to 2005.

Greenhouse gas concentrations:

 

[BillTre]

I want provable facts using known information that reaches actual conclusions, that everyone knows is FACT!

This is an unobtainable goal in the modern world, especially when there are so many people with a variety of reasons to contest any particular fact that conflicts with something of import to them.
Example: flat earthers do not accept the Earth being round is a fact.
Alternatively, one could also hypothesize that you are not a human but some computer program posting here, thus disputing the "fact" that you are a human rather than a machine.
These kinds not serious kinds of arguments are pretty bogus.

Evolution is provable science fact, but evolving from one species to another is not. Yet some teach Darwin as if it was fact. The Japanese were considerably shorter than Americans in WWII, but after changing to our Western diet, they began growing taller...evolving. To jump from that fact to monkeys changing to human is a serious stretch.

This is wrong in many ways:
How is it that species are not evolving into different species if evolution is a provable fact?
How is it that evolution is a provable fact if Darwin was not right (on most things)?
Perhaps this is some form of sarcasm on your part (I can't tell, if so my apologies).
Any changes in the height of a Japanese population does not have to be attributed to evolution rather than perhaps better nutrition or some other non-genetic, non-evolutionary cause.

 

[russ_watters]

.Scott, my real problem with so-called science on climate change is the reference to "consensus" among scientists. Science is the ability to perform a repeatable test in order to prove or disprove something. Supposedly, science is set-in-stone once the studies/tests are complete, and no guess-work is involved once that work is done.

Ok, so this is a broader problem than climate change itself, it's a misunderstanding of what science is/how it works. There is no such thing as set-in-stone in science. There is only a spectrum of confidence level in a theory.

More fuel with cooler denser air at a 14.7:1 ratio, makes for better combustion. That is science fact.

Correct, but this is data, not theory. Data is the facts of what happened, theory is the explanation. Data informs theory, but theory generally does not become data.

And even data isn't 100%. Data always has error associated with the measurement. This is a particular problem with climate change, where the data is noisy - it varies a lot on its own and the trend we're looking for is small.

That said, my understanding of the current state of the science is that the following are very solid:

• The data is has become clear that the climate is warming, and at a historic rate.
• The data is clear the CO2 (and other gases) are greennhouse gases because they block IR radiation.
• The data is clear that the concentration of CO2 (and other greenhouse gases) is rising and that measured human releases are most of it.
• Therefore, the theory that humans are causing global warming is very strongly accepted.

The reason you can't say this theory is as strong as, for example, Special Relativity, is that the data is noisy...not that it prevents crackpots from disbelief of Relativity. But you're unlikely to find a scientist in a relevant discipline anywhere who doesn't accept SR and only a very small handful who do not accept that humans are causing global warming.

Extending:

• The prediction based on that theory is something like 0.3C per decade for the next few decades.

Because the data is noisy and weather/climate is chaotic (there are a lot of variables), the confidence level in this prediction is high but not really high. And predictions of secondary and tertiary effects such as damage or cost are very low confidence (and many not even scientific anyway).

 

[PeterDonis]

The data is has become clear that the climate is warming, and at a historic rate.

I think the confidence in "the climate is warming" is high, but I don't think the confidence in "at a historic rate" (by which I think you mean "at a rate that is larger than what has been seen before in human history") is as high.

Therefore, the theory that humans are causing global warming is very strongly accepted.

There is a missing piece in the chain of reasoning here, though: how confident are we that there are no other drivers of climate change that are significant? The argument that there aren't, i.e., that CO2 is the only significant driver (and therefore human CO2 emissions are the only significant driver), depends on climate models, and climate model predictions based on CO2 being the only significant driver only match observed warming rates well in the latter half of the 20th century. Climate models under-predict warming for the early 20th century (because there wasn't much CO2 rise then, but there was significant warming) and over-predict warming for the early 21st century (because there has been signficant CO2 rise, but little to no warming). So our confidence in "humans are causing global warming" should not be as high as our confidence in "humans are causing most of the rise in CO2 levels"; or, to put it another way, the variance between model predictions and observations in the early 20th century and early 21st century should raise the significant possibility that there are other drivers of climate change that the models are not capturing, and we need to understand what those are.

 

[Genava]

There is a missing piece in the chain of reasoning here, though: how confident are we that there are no other drivers of climate change that are significant? The argument that there aren't, i.e., that CO2 is the only significant driver (and therefore human CO2 emissions are the only significant driver), depends on climate models, and climate model predictions based on CO2 being the only significant driver only match observed warming rates well in the latter half of the 20th century. Climate models under-predict warming for the early 20th century (because there wasn't much CO2 rise then, but there was significant warming) and over-predict warming for the early 21st century (because there has been signficant CO2 rise, but little to no warming). So our confidence in "humans are causing global warming" should not be as high as our confidence in "humans are causing most of the rise in CO2 levels"; or, to put it another way, the variance between model predictions and observations in the early 20th century and early 21st century should raise the significant possibility that there are other drivers of climate change that the models are not capturing, and we need to understand what those are.

I agree. It is why there is a lot of work around energy budget/balance of the Earth. And it is why I put these two publications in the first place:

Today, we have satellite data supporting that theory:
https://journals.ametsoc.org/doi/10.1175/2008BAMS2634.1

And direct measurement of the greenhouse effect in the atmosphere:
https://www.nature.com/articles/nature14240

Measuring the climate forcing parameters is one of the key topic to improve the models and the predictions. But is it to explain most of the warming? I don't think so. The uncertainties and variability in the models depend more on:
- Policy scenarios
- Heat redistribution on the Earth's surface
- Water-CO2 feedback
- Vegetation productivity feedback (related with the water cycle as well)
etc.

It is not really about possible unknown sources. It is about knowing how the system reacts with an increase of thermal energy. A warming of the air temperature is only one expression of this increase.

 

[Genava]

My issue is not with the facts but with how they are acquired.

First you told us you are looking for facts and now you are looking for something else... something else which is related to your distrust of a part of the scientific community based on ..? It is not science clearly.

 

[BillTre]

To evolve simply means change over time, and the Japanese grew taller only after switching to a more Western diet.

So, now you are using "evolve" (in a scientific forum where commonly understood meanings of words is important) to mean the same thing as "change"?
Why not use change, a simpler and more direct word? Change is used a lot in the scientific world using the meaning you explained.

So now you are denying evolution of life by natural selection based on a hoax no one believes and a bunch of not knowing about modern biology and human evolution.

Please educate yourself or stick to your primary issue here.

 

[Genava]

Genava, I am not looking for something else and I have faith in science...just not some who want more $$$ for their projects. However, I am skeptical about the numbers used, as are many in this debate. When I put numbers into a formula for say RPM at a given MPH, I must make sure "all" factors are included and correct. Final gear ratio, tire diameter, where (RPM) does the engine make max torque, am I using a true drag number for friction on the ground and air-drag, is my frontal area number right, and on it goes. And that is just for a motor vehicle speed/rpm relation. ANY of those number changes can drastically alter RPM or MPH or both. Those of us over 60 can remember the lies, yes lies, we were told in the 70's about America freezing by the year 2000. That did instill a degree of skepticism. Water boils at 212f and freezes at 32f...FACT, unless one injects gasses or anti-freeze, or some other outside influence. That is the kind of certainty I am looking to see. I TRUST science, but not scientists. I am here because I have watched this site for some time and trust the people. If I sometimes sound distrusting, it is not aimed at people here.

Ok. Then for example there are several introductory articles about climate change on the webpage of the American Chemical Society, what do you think of them?
https://www.acs.org/content/acs/en/climatescience/climatesciencenarratives.html

 

[russ_watters]

I don't think that this supports your statement that the US has "dropped its [C]O2 levels dramatically over the past 4 decades". Perhaps we've trimmed them.

This thread is moving fast so I may have missed the clearing-up of this one, but it is probably a reference to per capita carbon emissions, which have in fact been dropping for 45 years:
https://www.google.com/search?ei=Ff...4j2...0...1..gws-wiz...0i71j0i131.5uiuU4glwsg
[not sure how to embed this google chart, sorry]

This follows the peaking of per capita energy use, aka "energy intensity".

 

[OCR]

not sure how to embed this google chart, sorry

Screen shot ?

.

 

[DrClaude]

Thread closed pending moderation.

 

[berkeman]

After a long Mentor discussion, the thread will remain closed.