Climate Model Credibility Gap The Resilient Earth (H/T crick)
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Marine and terrestrial proxy records suggest that there was a peak in global warming between 10,000 and 6,000 years ago, following the end of the last glacial period. Since the Holocene Thermal Maximum, Earth has undergone global cooling. The physical mechanism responsible for this global cooling has remained unknown and doesn't fit in with the current CO2 based climate models. Those climate models generate a robust global annual mean warming throughout the Holocene, mainly in response to rising CO2 levels and albedo changes due to retreating of ice sheets. In other words, the models disagree with reality, and when models disagree with nature the models have a credibility gap. A new paper in the Proceedings of the National Academy of Sciences (PNAS) says this model-data inconsistency indicates a critical reexamination of both proxy data and models is called for.
The fact that all the world's complex and expensive climate models can't explain climate change since the last glacial period ended is one of the little talked about embarrassments of climate science. In a new study, soon to be published in PNAS, a team led by Zhengyu Liu, a researcher at the Nelson Center for Climatic Research and Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, has come out of the modeling closet to examine the model-data inconsistency.
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what does this mean? it means that the current CO2 theory and feedbacks due to receding ice, etc predict that the Holocene should have continued to warm for the last ten thousand years instead of the early peak and slow decline shown by the proxies.
here is the PNAS paper and SI. http://www.pnas.org/content/111/34/E3501.full.pdf?with-ds=yes
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Abstract
A recent temperature reconstruction of global annual temperature shows Early Holocene warmth followed by a cooling trend through the Middle to Late Holocene [Marcott SA, et al., 2013, Science 339(6124):1198–1201]. This global cooling is puzzling because it is opposite from the expected and simulated global warming trend due to the retreating ice sheets and rising atmospheric greenhouse gases. Our critical reexamination of this contradiction between the reconstructed cooling and the simulated warming points to potentially significant biases in both the seasonality of the proxy reconstruction and the climate sensitivity of current climate models.
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Significance
Marine and terrestrial proxy records suggest global cooling during the Late Holocene, following the peak warming of the Holocene Thermal Maximum (∼10 to 6 ka) until the rapid warming induced by increasing anthropogenic greenhouses gases. However, the physical mechanism responsible for this global cooling has remained elusive. Here, we show that climate models simulate a robust global annual mean warming in the Holocene, mainly in response to rising CO2 and the retreat of ice sheets. This model-data inconsistency demands a critical reexamination of both proxy data and models.
"
it is common for the climate models to produce results that kinda, sorta look almost right if you squint your eyes in the right way, but they miss out on the actual important 'shape' of climate change. big volcanic eruptions are like this. the models produce gradual changes that are smaller and spread out more over time. reality is more abrupt with quick return to stasis. this pnas paper points out that there are major mechanisms still undiscovered, and that climate forcings as we define them in IPCC etc are insufficient for purpose. the idea that we can forecast future climate change with any reasonable skill or certainty is preposterous.
"
Marine and terrestrial proxy records suggest that there was a peak in global warming between 10,000 and 6,000 years ago, following the end of the last glacial period. Since the Holocene Thermal Maximum, Earth has undergone global cooling. The physical mechanism responsible for this global cooling has remained unknown and doesn't fit in with the current CO2 based climate models. Those climate models generate a robust global annual mean warming throughout the Holocene, mainly in response to rising CO2 levels and albedo changes due to retreating of ice sheets. In other words, the models disagree with reality, and when models disagree with nature the models have a credibility gap. A new paper in the Proceedings of the National Academy of Sciences (PNAS) says this model-data inconsistency indicates a critical reexamination of both proxy data and models is called for.
The fact that all the world's complex and expensive climate models can't explain climate change since the last glacial period ended is one of the little talked about embarrassments of climate science. In a new study, soon to be published in PNAS, a team led by Zhengyu Liu, a researcher at the Nelson Center for Climatic Research and Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, has come out of the modeling closet to examine the model-data inconsistency.
"
what does this mean? it means that the current CO2 theory and feedbacks due to receding ice, etc predict that the Holocene should have continued to warm for the last ten thousand years instead of the early peak and slow decline shown by the proxies.
here is the PNAS paper and SI. http://www.pnas.org/content/111/34/E3501.full.pdf?with-ds=yes
"
Abstract
A recent temperature reconstruction of global annual temperature shows Early Holocene warmth followed by a cooling trend through the Middle to Late Holocene [Marcott SA, et al., 2013, Science 339(6124):1198–1201]. This global cooling is puzzling because it is opposite from the expected and simulated global warming trend due to the retreating ice sheets and rising atmospheric greenhouse gases. Our critical reexamination of this contradiction between the reconstructed cooling and the simulated warming points to potentially significant biases in both the seasonality of the proxy reconstruction and the climate sensitivity of current climate models.
"
and
"
Significance
Marine and terrestrial proxy records suggest global cooling during the Late Holocene, following the peak warming of the Holocene Thermal Maximum (∼10 to 6 ka) until the rapid warming induced by increasing anthropogenic greenhouses gases. However, the physical mechanism responsible for this global cooling has remained elusive. Here, we show that climate models simulate a robust global annual mean warming in the Holocene, mainly in response to rising CO2 and the retreat of ice sheets. This model-data inconsistency demands a critical reexamination of both proxy data and models.
"
it is common for the climate models to produce results that kinda, sorta look almost right if you squint your eyes in the right way, but they miss out on the actual important 'shape' of climate change. big volcanic eruptions are like this. the models produce gradual changes that are smaller and spread out more over time. reality is more abrupt with quick return to stasis. this pnas paper points out that there are major mechanisms still undiscovered, and that climate forcings as we define them in IPCC etc are insufficient for purpose. the idea that we can forecast future climate change with any reasonable skill or certainty is preposterous.
