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Thread: Climate Science’s Myth-Buster

  1. #11
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    Quote Originally Posted by skepticalmike View Post
    There is one paragraph in this article that interests me and I went to Judith Curry's blog to learn more about it. I have also consulted other sources for information. The first half of the 20th

    century is a bit of a conundrum. I will post another message or 2 when I get a better understanding. This is the paragraph:

    Between 1910 and 1940, the planet warmed during a climatic episode that resembles our own, down to the degree. The warming can’t be blamed on industry, she argues, because back then, most of the carbon-dioxide emissions from burning fossil fuels were small. In fact, Curry says, “almost half of the warming observed in the twentieth century came about in the first half of the century, before carbon-dioxide emissions became large.” Natural factors thus had to be the cause. None of the climate models used by scientists now working for the United Nations can explain this older trend. Nor can these models explain why the climate suddenly cooled between 1950 and 1970, giving rise to widespread warnings about the onset of a new ice age. I recall magazine covers of the late 1960s or early 1970s depicting the planet in the grip of an annihilating deep freeze. According to a group of scientists, we faced an apocalyptic environmental scenario—but the opposite of the current one

    Natural factors were part of the cause. Even Judith Curry acknowledges that so the author is stretching the truth to claim that only natural factors can account for global warming in the first half

    of the 20th century. Some analysis have shown that approximately 50% of the warming was due to anthropogenic causes. There are also questions about the accuracy of the observations and

    Judith Curry picks a relative minimum point (1910) to begin the time period under analysis and ends the analysis when there was an anomalous spike in temperature. That produced a 1.2

    degree F. temperature increase which could overstate the temperature rise.
    Some computer models of the climate have reproduced the early 20th century fairly well. Some of the cooling during the middle of the 20th century has been attributed to stratospheric

    aerosols caused by increased air pollution following economic recovery after world War II. Magazine covers predicting a "coming ice age or a deep freeze" was not representative of the opinions

    of the climate science community during the 1970's.

    Sea level rise has been accelerating, contrary to what was stated in that article

    What myth or myths has Judith Curry busted? The author never states what the myths are. She has raised questions about climate science but it isn't clear to me that she has debunked

    anything.

    The consensus myth. There are no doubt some scientists who analyze the first half of the 20th century the way Curry does and, as you point out, some who do not. Let's accept that as true and then conclude from that observation that the modern climate consensus is myth.
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    What if you're wrong? Which is the safer course? To assume that all climate change science that you don't agree with is BS or to act like good stewards of the planet?
    "The difference between what we do and what we are capable of doing would suffice to solve most of the world’s problems.”
    Mahatma Gandhi

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    Quote Originally Posted by Dr. Who View Post
    What if you're wrong? Which is the safer course? To assume that all climate change science that you don't agree with is BS or to act like good stewards of the planet?
    So you think socialism is the safer course then? That's what's behind the politically-driven consensus.

    BTW, I'm a climate lukewarmist like Bjorn Lomborg. Why do you assume either/or, right/wrong, alarmist/denier?
    Edmund Burke: "In vain you tell me that Artificial Government is good, but that I fall out only with the Abuse. The Thing! the Thing itself is the Abuse!"

  4. The Following User Says Thank You to Chris For This Useful Post:

    MisterVeritis (10-30-2019)

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    Quote Originally Posted by Chris View Post
    So you think socialism is the safer course then? That's what's behind the politically-driven consensus.

    BTW, I'm a climate lukewarmist like Bjorn Lomborg. Why do you assume either/or, right/wrong, alarmist/denier?
    Did I mention socialism - no. I did mention good stewardship. Just answer the question without the politics.
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    Quote Originally Posted by Dr. Who View Post
    Did I mention socialism - no. I did mention good stewardship. Just answer the question without the politics.
    Socialism is behind the politics of climate change.

    I answered your question, the implication is your plan is costly and would run us into the ground economically. Answer mine.
    Edmund Burke: "In vain you tell me that Artificial Government is good, but that I fall out only with the Abuse. The Thing! the Thing itself is the Abuse!"

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    Here is an article at the carbonbrief.org which can explain the warming of the first half of the twentieth century.https://www.carbonbrief.org/guest-post-why-natural-cycles-only-play-small-
    role-in-rate-of-global-warming


    The role of variability due to natural ocean cycles in global warming is a long-standing debate in climate science.The scientific community overwhelmingly agrees that human activities are responsible for the observed increase in temperatures for the last half-century. However, the relative influences of natural drivers of climate change – such as volcanic eruptions, ocean cycles, and the sun – on warmer and cooler phases superimposed on the long-term warming trend is still an area of active research.In a paper published in the Journal of Climate, we find that the combination of human and natural climate forcings – increased atmospheric CO2 and other greenhouse gases, volcanoes, solar activity and aerosols – can explain virtually all of the long-term change in the temperature record over the past 150 years.While year-to-year ups and downs are related to the El Niño-Southern Oscillation (ENSO) phenomenon, we find that variability due to slow-acting ocean cycles is not necessary to explain the longer-term changes in the historical temperature record.

    Model matches observed warming
    The “early warming period” between 1915 and 1945 has long been a challenge for scientists to explain. Prior studies have suggested that about half the observed warming during this period is attributable to factors that are “external” to the climate – such as human-caused greenhouse gas emissions, volcanic eruptions and variability in the sun’s output. The remaining half are attributed to “internal” factors – natural fluctuations within the climate system itself. This has led to suggestions that there may be long-term ocean cycles operating over 60- to 70-year periods which influence global temperatures. They are commonly associated with the Atlantic Multidecadal Variability index (AMV).Our findings challenge this prevailing view. We find that virtually all of the observed changes in global average temperatures over the past 170 years are caused by external drivers, leaving little room for an “unforced” internal ocean contribution. This means that ocean cycles on timescales of 60-70 years are unlikely to be a factor in the observed evolution of global temperatures since 1850. Instead, external factors, such as periods of strong volcanic activity and the release of aerosol particles (air pollution), have caused temperatures to fluctuate.

    In our model, virtually all (97-98%) of the long-term changes in temperature can be explained by external forcing. This approach uses a more precise description of the anthropogenic aerosol feedback processes (warming effect of black-carbon pollution and cooling effect of sulphate particles from industrial combustion) and removes biases in sea surface temperature (SST) records caused by a change in the way measurements were taken around the second world war. However, even without these updated forcings and observational estimates, this approach captures a substantial portion of the variability in global temperature.The model effectively matches temperatures over both land and ocean. (see the article at carbonbrief for the graphs)

    The graphs below are from the Journal of Climate: A Limited Role for Unforced Internal Variability in Twentieth-Century Warminghttps://journals.ametsoc.org/doi/ful...18-0555.1?af=R


    Last edited by skepticalmike; 10-30-2019 at 01:39 AM.

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    Another article on this subject is at realclimate.org. I haven't had time to read the article from the previous post published in the Journal of Climate but I have read the articles at carbon brief and realclimate.org. I will discuss this in a later post.

    http://www.realclimate.org/index.php/archives/2019/06/unforced-variations-vs-forced-responses/#more-22424


    Until recently, the hypothesis that there are significant natural (unforced) ocean cycles with an approximate periodicity of 60-70 years had been widely accepted. The so-called Atlantic Multidecadal Variability index (AMV, sometimes called the AMO instead), but also the Pacific Decadal Variability index (PDV) have been touted as major factors in observed multidecadal GMST fluctuations (for instance, here). Due to the strong co-variability between AMV and GMST, both, the Early 20th Century Warming (1915-1945) and the Mid-Century Cooling (1950-1980) have been attributed to low-frequency AMV variability, associated to a varying degree with changes in the Atlantic Meridional Overturning Circulation (AMOC). In particular, the uncertainty in quantifying the human-induced warming fraction in the early 20th Century was still substantial.

    In contrast to those earlier studies, we were able to reproduce effectively all the observed multidecadal temperature evolution, including the Early Warming and the Mid-Century cooling, using known external forcing factors (solar activity, volcanic eruptions, greenhouse gases, pollution aerosol particles). Adding an El Niño signal, we virtually explain the entire observed record (Figure 1). Further, we were able to reproduce the temperature evolution separately over land and ocean, and between Northern and Southern Hemispheres (NH/SH). We found equally high fractions of explained variability associated with anthropogenic and natural radiative forcing changes in each case. Attributing 90% of the Early Warming to external forcings (50% of which is due to natural forcing from volcanoes and solar) is – in our view – a key leap forward. To date, no more than 50% had been attributed to external forcing (Hegerl et al. 2018). While there is less controversy about the drivers of the Mid-Century cooling, our response model results strongly support the idea that the trend was caused by increased levels of sulphate aerosols which temporarily offset greenhouse gas-induced warming.
    What does this mean?
    Some commentators have used the uncertainty in the attribution for the Early 20th Century warming as an excuse to not accept the far stronger evidence for the human causes of more recent trends (notably, Judith Curry).


    Fig. 1: Matches of modeled temperature to the observations since 1850.
    Upper graph shows the global response model with ENSO (bold green) compared to HadOST (bold black). Lower graph is the same as above but with lowess smoothed observational data. The response model results (green thin lines) represent the parameter uncertainty for an associated TCR of 1.6K. The dashed thin line is the upper and lower (reasonable) bound for the effective aerosol forcing for 2017 (-0.5 and -1.0 W/m2), in contrast to the best estimate of -0.75 W/m2 used in the response model. The grey area indicates the 5-95th percentile of the total uncertainty. The two graphs are offset by 0.9°C without a particular baseline. Response model and observations are aligned for the 1901-2000 period.
    Last edited by skepticalmike; 10-30-2019 at 01:56 AM.

  9. #18
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    Quote Originally Posted by skepticalmike View Post
    Here is an article at the carbonbrief.org which can explain the warming of the first half of the twentieth century.https://www.carbonbrief.org/guest-post-why-natural-cycles-only-play-small-
    role-in-rate-of-global-warming


    The role of variability due to natural ocean cycles in global warming is a long-standing debate in climate science.The scientific community overwhelmingly agrees that human activities are responsible for the observed increase in temperatures for the last half-century. However, the relative influences of natural drivers of climate change – such as volcanic eruptions, ocean cycles, and the sun – on warmer and cooler phases superimposed on the long-term warming trend is still an area of active research.In a paper published in the Journal of Climate, we find that the combination of human and natural climate forcings – increased atmospheric CO2 and other greenhouse gases, volcanoes, solar activity and aerosols – can explain virtually all of the long-term change in the temperature record over the past 150 years.While year-to-year ups and downs are related to the El Niño-Southern Oscillation (ENSO) phenomenon, we find that variability due to slow-acting ocean cycles is not necessary to explain the longer-term changes in the historical temperature record.

    Model matches observed warming
    The “early warming period” between 1915 and 1945 has long been a challenge for scientists to explain. Prior studies have suggested that about half the observed warming during this period is attributable to factors that are “external” to the climate – such as human-caused greenhouse gas emissions, volcanic eruptions and variability in the sun’s output. The remaining half are attributed to “internal” factors – natural fluctuations within the climate system itself. This has led to suggestions that there may be long-term ocean cycles operating over 60- to 70-year periods which influence global temperatures. They are commonly associated with the Atlantic Multidecadal Variability index (AMV).Our findings challenge this prevailing view. We find that virtually all of the observed changes in global average temperatures over the past 170 years are caused by external drivers, leaving little room for an “unforced” internal ocean contribution. This means that ocean cycles on timescales of 60-70 years are unlikely to be a factor in the observed evolution of global temperatures since 1850. Instead, external factors, such as periods of strong volcanic activity and the release of aerosol particles (air pollution), have caused temperatures to fluctuate.

    In our model, virtually all (97-98%) of the long-term changes in temperature can be explained by external forcing. This approach uses a more precise description of the anthropogenic aerosol feedback processes (warming effect of black-carbon pollution and cooling effect of sulphate particles from industrial combustion) and removes biases in sea surface temperature (SST) records caused by a change in the way measurements were taken around the second world war. However, even without these updated forcings and observational estimates, this approach captures a substantial portion of the variability in global temperature.The model effectively matches temperatures over both land and ocean. (see the article at carbonbrief for the graphs)

    The graphs below are from the Journal of Climate: A Limited Role for Unforced Internal Variability in Twentieth-Century Warminghttps://journals.ametsoc.org/doi/ful...18-0555.1?af=R



    Right, so a single study offers a contrary conclusion. Single studies aren't what make science science. It remains true even as they say that "The “early warming period” between 1915 and 1945 has long been a challenge for scientists to explain."
    Edmund Burke: "In vain you tell me that Artificial Government is good, but that I fall out only with the Abuse. The Thing! the Thing itself is the Abuse!"

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    Quote Originally Posted by Common Sense View Post
    It's interesting how your views on climate change alter once you start working for the fossil fuel industry, like Curry does. But I'm sure the fact that much of her research is funded by the oil and gas industry has had no effect on her conclusions.
    Maybe it's just a matter of gaining perspective. A matter of learning that all you once thought was true -- is changing.
    "What happens is of little significance compared with the stories we tell ourselves about what happens. Events matter little, only stories of events
    affect us.”

    ~Rabih Alameddin


  11. #20
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    Quote Originally Posted by skepticalmike View Post
    Another article on this subject is at realclimate.org. I haven't had time to read the article from the previous post published in the Journal of Climate but I have read the articles at carbon brief and realclimate.org. I will discuss this in a later post.

    http://www.realclimate.org/index.php/archives/2019/06/unforced-variations-vs-forced-responses/#more-22424


    Until recently, the hypothesis that there are significant natural (unforced) ocean cycles with an approximate periodicity of 60-70 years had been widely accepted. The so-called Atlantic Multidecadal Variability index (AMV, sometimes called the AMO instead), but also the Pacific Decadal Variability index (PDV) have been touted as major factors in observed multidecadal GMST fluctuations (for instance, here). Due to the strong co-variability between AMV and GMST, both, the Early 20th Century Warming (1915-1945) and the Mid-Century Cooling (1950-1980) have been attributed to low-frequency AMV variability, associated to a varying degree with changes in the Atlantic Meridional Overturning Circulation (AMOC). In particular, the uncertainty in quantifying the human-induced warming fraction in the early 20th Century was still substantial.

    In contrast to those earlier studies, we were able to reproduce effectively all the observed multidecadal temperature evolution, including the Early Warming and the Mid-Century cooling, using known external forcing factors (solar activity, volcanic eruptions, greenhouse gases, pollution aerosol particles). Adding an El Niño signal, we virtually explain the entire observed record (Figure 1). Further, we were able to reproduce the temperature evolution separately over land and ocean, and between Northern and Southern Hemispheres (NH/SH). We found equally high fractions of explained variability associated with anthropogenic and natural radiative forcing changes in each case. Attributing 90% of the Early Warming to external forcings (50% of which is due to natural forcing from volcanoes and solar) is – in our view – a key leap forward. To date, no more than 50% had been attributed to external forcing (Hegerl et al. 2018). While there is less controversy about the drivers of the Mid-Century cooling, our response model results strongly support the idea that the trend was caused by increased levels of sulphate aerosols which temporarily offset greenhouse gas-induced warming.
    What does this mean?
    Some commentators have used the uncertainty in the attribution for the Early 20th Century warming as an excuse to not accept the far stronger evidence for the human causes of more recent trends (notably, Judith Curry).


    Fig. 1: Matches of modeled temperature to the observations since 1850.
    Upper graph shows the global response model with ENSO (bold green) compared to HadOST (bold black). Lower graph is the same as above but with lowess smoothed observational data. The response model results (green thin lines) represent the parameter uncertainty for an associated TCR of 1.6K. The dashed thin line is the upper and lower (reasonable) bound for the effective aerosol forcing for 2017 (-0.5 and -1.0 W/m2), in contrast to the best estimate of -0.75 W/m2 used in the response model. The grey area indicates the 5-95th percentile of the total uncertainty. The two graphs are offset by 0.9°C without a particular baseline. Response model and observations are aligned for the 1901-2000 period.

    Some commentators have used the uncertainty in the attribution for the Early 20th Century warming as an excuse to not accept the far stronger evidence for the human causes of more recent trends (notably, Judith Curry).
    Except that's not what Curry claimed. Her claim is focused on a single factor: "Curry says, 'almost half of the warming observed in the twentieth century came about in the first half of the century, before carbon-dioxide emissions became large.'"
    Edmund Burke: "In vain you tell me that Artificial Government is good, but that I fall out only with the Abuse. The Thing! the Thing itself is the Abuse!"

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