Curry More on the GCM Models
The ECS or equilibrium CS is used pretty extensively here, while the TCS or transient CS is used elsewhere. Have not seen a treatment of how they might differ.
Her treatment of the non-linearity and the ultimate complexity and extreme difficulty in predicting climate is good. Recent papers showing a reduced CS are coming forward. The cycles of the ocean would be to list, given that apparently some are on the scale of millennia.
http://www.thegwpf.org/content/uploads/2017/02/Curry-2017.pdf
The number of cells in the grid system determines the model‘ resolution’ (or granularity), whereby each grid cell effectively has a uniform temperature, and so on. Common resolutions for GCMs are about 100–200km in the horizontal direction, 1km vertically, and a time-stepping resolution typically of 30min. While at higher resolutions, GCMs represent processes somewhat more realistically, the computing time required to do the calculations increases substantially – a doubling of resolution requires about 10 times more computing power, which is currently infeasible at many climate modeling centers.
The coarseness of the model resolution is driven by the available computer resources, with tradeoffs made between model resolution, model complexity, and the length and number of simulations to be conducted. Because of the relatively coarse spatial and temporal resolutions of the models, there are many important processes that occur on scales that are smaller than the model resolution (such as clouds and rainfall; see inset in Figure1).
These subgrid – scale processes are represented using‘ parameterizations’, which are simple formulas that attempt to approximate the actual processes, based on observations or derivations from more detailed process models. These parameterizations are ‘calibrated’ or ‘tuned’ to improve the comparison of the climate model outputs against historical observations.
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Other recent papers also find comparably low values of ECS, 9,10 and the latest research suggests even lower values. The greatest uncertainty in ECS estimates is in accounting for the effects of small aerosol particles in the atmosphere (from pollution or natural sources), which have a cooling effect on the climate (partially counter acting the greenhouse warming). A recent paper by IPCC lead author Stevens 11 constrains the impact of aerosols on climate to be significantly smaller than assumed in the Fifth Assessment Report. Lewis has re-run the calculations used in Lewis and Curry (2014) using aerosol impact estimates in line with Stevens’ paper. 12 Most significantly, the upper bound (95thpercentile) is lowered to 2.38◦C (Table1).
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What is the source of the discrepancies in ECS among different climate models, and between climate models and observations? In a paper entitled ‘What are climate models missing?’ 14 Stevens and Bony argue that: There is now ample evidence that an inadequate representation of clouds and moist convection, or more generally the coupling between atmospheric water and circulation, is the main limitation in current representations of the climate system. What are the implications of these discrepancies for the value of ECS?
If it is less than 2◦C versus more than 4◦C, then the conclusions regarding the causes of 20th century warming and the likely amount of 21st century warming are substantially different. Further, the discrepancy between observational and GCM estimates of climate sensitivity is substantial and of significant importance to policy makers. ECS and the level of uncertainty in its value are key inputs into the economic models that drive cost– benefit analyses and estimates of the social cost of carbon.
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Variations in climate can be caused by external forcing, such as solar variations, volcanic eruptions or changes in atmospheric composition such as an increase in carbon dioxide. Climate can also change owing to internal processes within the climate system (internal variability). The best-known example of internal climate variability is El Niño/La Niña. Modes of decadal to centennial to millennial internal variability arise from the slow circulations in the oceans.
As such, the ocean serves as a ‘fly wheel’ on the climate system, storing and releasing heat on long timescales and acting to stabilize the climate. As a result of the time lags and storage of heat in the ocean, the climate system is never in equilibrium. With regards to multi-decadal internal variability, the IPCC reports consider this issue primarily in context of detection of a human-caused warming signal above the background ‘noise’ of natural variability. However, other interpretations of the climate system argue that the natural internal variability constitutes the intrinsic climate signal.
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The IPCC’s projections of 21st century climate change explicitly assume that carbon dioxide is the control knob for global climate. Climate model projections of the 21st century climate are not convincing because of:
• failure to predict the warming slowdown in the early 21st century
• inability to simulate the patterns and timing of multi-decadal ocean oscillations
• lack of account for future solar variations and solar indirect effects on climate
• neglect of the possibility of volcanic eruptions that are more active than the relatively quiet 20th century
• apparent over sensitivity to increases in greenhouse gases
We should revisit occasionally what the proper role of government is. As the constitution was a good sense of direction, we need a core set of principles to add in order to deal with the future.
So many want to engineer society, remove risk, assist certain groups, rather than let individuals thrive and raise communities. Why?
Is Democracy where we all "get it good and hard" or is it the best means to a free society?
Should we roll with the special interests, or make the government achieve its proper role, what is that role, and how to do this?
When do deficits and governments become too large?
Government is becoming more elitist while trying to sell corrections to problems it created, what makes this possible?
This could also be inserted into the field above, or erased
Currently as a society, we are having a most difficult time discussing political issues. What is driving this? And why a rebirth in political culture would be a good thing.
Are "markets" dead as some would conjecture? Or is free enterprise what got us here?
At the heart of economics there are several possible economic schools of thought, the essence of these schools of thought and how they relate to our lives.
