Fingerprints of man-made global warming

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Bootstrap
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Fingerprints of man-made global warming

Post by Bootstrap »

I would like to try another thread limited to discussing data, following Peter's lead.

Rules for this thread:
  • Every post in this thread should address the scientific claims made below
  • Do not attempt to discredit individuals or groups in this thread
  • Focus on the data, not on each other
IPCC wrote:It is extremely likely [95 percent confidence] more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together.
We can distinguish human contributions from natural causes:
IPCC wrote:The best estimate of the human-induced contribution to warming is similar to the observed warming over this period ... The observed warming since 1951 can be attributed to the different natural and anthropogenic drivers and their contributions can now be quantified. Greenhouse gases contributed a global mean surface warming likely to be in the range of 0.5°C to 1.3 °C over the period 1951−2010, with the contributions from other anthropogenic forcings, including the cooling effect of aerosols, likely to be in the range of −0.6°C to 0.1°C.
Natural external factors like solar activity and natural internal factors like ocean cycles are not causing global warming.
IPCC wrote:The contribution from natural forcings is likely to be in the range of −0.1°C to 0.1°C, and from internal variability is likely to be in the range of −0.1°C to 0.1°C.
These are the key claims of the IPCC. Some people are challenging these claims.

This graph summarizes these claims:

Image
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ken_sylvania
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Re: Fingerprints of man-made global warming

Post by ken_sylvania »

IPCC wrote:The best estimate of the human-induced contribution to warming is similar to the observed warming over this period ... The observed warming since 1951 can be attributed to the different natural and anthropogenic drivers and their contributions can now be quantified. Greenhouse gases contributed a global mean surface warming likely to be in the range of 0.5°C to 1.3 °C over the period 1951−2010, with the contributions from other anthropogenic forcings, including the cooling effect of aerosols, likely to be in the range of −0.6°C to 0.1°C.
So if greenhouse gasses warm the earth by 0.5°C and aerosols cool the earth by -0.6°C, makes a net contribution of -0.1°C, right? :)
The report says that we can differentiate between human caused warming/cooling vs. naturally caused warming/cooling, but then says that we can't accurately tell how much of the greenhouse gas warming is masked by aerosol cooling.

Does the report discuss the methods of fingerprinting causes at all? I didn't see anything about it in my initial read-through.
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Re: Fingerprints of man-made global warming

Post by Josh »

One wonders how humans are not part of "natural causes", especially if one believes we just got here by chance and that God didn't make humans, and make us special and different from the rest of nature.
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Re: Fingerprints of man-made global warming

Post by Wayne in Maine »

Bootstrap wrote:I would like to try another thread limited to discussing data, following Peter's lead.

Rules for this thread:
  • Every post in this thread should address the scientific claims made below
  • Do not attempt to discredit individuals or groups in this thread
  • Focus on the data, not on each other
IPCC wrote:It is extremely likely [95 percent confidence] more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together.
We can distinguish human contributions from natural causes:
IPCC wrote:The best estimate of the human-induced contribution to warming is similar to the observed warming over this period ... The observed warming since 1951 can be attributed to the different natural and anthropogenic drivers and their contributions can now be quantified. Greenhouse gases contributed a global mean surface warming likely to be in the range of 0.5°C to 1.3 °C over the period 1951−2010, with the contributions from other anthropogenic forcings, including the cooling effect of aerosols, likely to be in the range of −0.6°C to 0.1°C.
Natural external factors like solar activity and natural internal factors like ocean cycles are not causing global warming.
IPCC wrote:The contribution from natural forcings is likely to be in the range of −0.1°C to 0.1°C, and from internal variability is likely to be in the range of −0.1°C to 0.1°C.
These are the key claims of the IPCC. Some people are challenging these claims.

This graph summarizes these claims:

Image
These are indeed assertions, not scientific observations. The models on which global warming assertions are based are simply not good enough to support the 95% confidence of those assertions. There is not even a true "consensus" on how much warming the globe has experienced over the past few decades especially with data sets being "tuned" (we called that fudging when I was in University). And the models, when applied to real data, rarely if ever math real-world measurements of warming (except when the real-world data is adjusted to fit a particular model).
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Re: Fingerprints of man-made global warming

Post by Bootstrap »

ken_sylvania wrote:So if greenhouse gasses warm the earth by 0.5°C and aerosols cool the earth by -0.6°C, makes a net contribution of -0.1°C, right? :)
Obviously, you have some factors warming the earth, others cooling it, and they all have to add up to the amount of warming that has been measured. Imagine you have a closed room with a heater and an air conditioner. Imagine that you know that running the air conditioner for 5 minutes will lower the temperature by 2 degrees if there is no heater, but you do not know how much running the heater will raise the temperature. If you run both for 5 minutes and the temperature is up by 4 degrees, then the heater raised the temperature by 6 degrees - 2 degrees to fight the air conditioner, 4 degrees to raise the temperature above what it was.

Now imagine that you only know that the air conditioner will cool somewhere between 0 and 2 degrees, and the room warms by only 1 degree. Then the heater raised the temperature somewhere between 1 and 3 degrees.

Of course, there are many more factors, and they all have to balance out.

Incidentally, this is an example of a "model". If I can't directly measure the effects of each part of the system, I can infer parts of it by seeing how they add up.
Last edited by Bootstrap on Fri Mar 10, 2017 9:05 am, edited 1 time in total.
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Re: Fingerprints of man-made global warming

Post by Bootstrap »

Wayne in Maine wrote:These are indeed assertions, not scientific observations.
I called them claims. Claims are not scientific observations. I believe they are based on observations, but exploring the level of evidence for them is the purpose of this thread.
Wayne in Maine wrote:The models on which global warming assertions are based are simply not good enough to support the 95% confidence of those assertions. There is not even a true "consensus" on how much warming the globe has experienced over the past few decades especially with data sets being "tuned" (we called that fudging when I was in University). And the models, when applied to real data, rarely if ever math real-world measurements of warming (except when the real-world data is adjusted to fit a particular model).
Those are also claims, not scientific observations, and I think claims that most scientists would disagree with. I think we have to start by looking at the claims from the OP in more detail before - including their scientific basis - before we can evaluate them.
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Re: Fingerprints of man-made global warming

Post by Bootstrap »

ken_sylvania wrote:Does the report discuss the methods of fingerprinting causes at all? I didn't see anything about it in my initial read-through.
Were you reading the Summary for Policy Makers? It summarizes the work of several working groups. A good way to get an overview of the many kinds of data behind this is to look at the outline for

Working Group 1: The Physical Science Basis

You can see that at various levels of depth. You could use this diagram as an overview, go to that outline, and drill down into the information for each part to see the kinds of fingerprints they are looking at.

Image

I think their FAQ is a pretty useful overview of the kinds of evidence behind this:

The Physical Science Basis: Frequently Asked Questions

You can also find the papers, how they were evaluated and compared, etc. from that site by clicking around.
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Re: Fingerprints of man-made global warming

Post by appleman2006 »

And yet the guy portraying your side in Peter's example of a debate clearly admitted that the models do not hold up very well. Did he not?
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Re: Fingerprints of man-made global warming

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appleman2006 wrote:And yet the guy portraying your side in Peter's example of a debate clearly admitted that the models do not hold up very well. Did he not?
I generally agree with Kerry (GuestE), who said this:
GuestE: Let me just preface my answer here to your important question by saying that a lot of what we know about the climate system was predicted long before there was such a thing as a climate model. It's a mistake to think that everything we knew about climate or predictions about climate are based on complicated models. Having said that, we have built over the years a hierarchy of increasingly complex models that really are some of the most complicated pieces of software that the human race has ever constructed. They have their origins in models that were built for a much more pedestrian but important purpose, which is weather forecasting. And they are very complex. In the case of weather forecasting, arguably you can test them twice a day and see how well they are doing. With climate, it's much more difficult to test them because we don't have that many climate states. But we do experiments that are much along the lines of what you had just described as done with economic models. We try to hold certain variables constant, like sunlight. And vary another external factor, like carbon dioxide, to see how the system responds.
Christy (GuestC) emphasized that we cannot exactly calculate these things, though we do know the formulas (unlike economics):
GuestC: Uh, no, it isn't the same. Because there is a huge difference between climate modeling and economic modeling. We know the equations. You guys don't. Okay? And we actually know the equations we are trying to solve. And the problems come with actually trying to solve them. And arguably our computers aren't nearly powerful enough to really solve them exactly; and they won't be for generations, unless there is some unbelievable breakthrough in computation.
Kerry (GuestE) replied that may not be able to calculate these things exactly, but we don't need to either, because the predictions are robust even if the exact numbers change some. And you don't need really complicated models for much of this, simple models work just fine.
GuestE: Let me just preface my answer here to your important question by saying that a lot of what we know about the climate system was predicted long before there was such a thing as a climate model. It's a mistake to think that everything we knew about climate or predictions about climate are based on complicated models. Having said that, we have built over the years a hierarchy of increasingly complex models that really are some of the most complicated pieces of software that the human race has ever constructed. They have their origins in models that were built for a much more pedestrian but important purpose, which is weather forecasting. And they are very complex. In the case of weather forecasting, arguably you can test them twice a day and see how well they are doing. With climate, it's much more difficult to test them because we don't have that many climate states. But we do experiments that are much along the lines of what you had just described as done with economic models. We try to hold certain variables constant, like sunlight. And vary another external factor, like carbon dioxide, to see how the system responds.
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Re: Fingerprints of man-made global warming

Post by Robert »

Unless, say, the Earth's mantle is maybe 110 degrees C hotter than expected. Then the models will be a good bit off since those are base foundational constants that much is based off of.
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