In a study published in Environmental Research Letters, Cohen et al. (2012) note that over the last four decades Arctic temperatures have warmed at nearly double the global rate, citing Solomon et al. (2007) and Screen and Simmonds (2010); and they state that “coupled climate models attribute much of this warming to rapid increases in greenhouse gases and project the strongest warming across the extratropical Northern Hemisphere during boreal winter due to ‘winter (or Arctic) amplification’,” citing Holland and Bitz (2003), Hansen and Nazarenko (2004), Alexeev et al. (2005) and Langen and Alexeev (2007).
However, they say that “recent trends in observed Northern Hemisphere winter surface temperatures diverge from these projections,” noting that “while the planet has steadily warmed, Northern Hemisphere winters have recently grown more extreme across the major industrialized centers,” and reporting that “record cold snaps and heavy snowfall events across the United States, Europe and East Asia garnered much public attention during the winters of 2009/10 and 2010/11 (Blunden et al., 2011; Cohen et al., 2010),” with the latter set of researchers suggesting that “the occurrence of more severe Northern Hemisphere winter weather is a two-decade-long trend starting around 1988.”
So what’s going on here?
Cohen et al. say that “whether the recent colder winters are a consequence of internal variability or a response to changes in boundary forcings resulting from climate change remains an open question.” But like most scientists who love to resolve dilemmas, they go on to propose their answer to the puzzle, suggesting that “summer and autumn warming trends are concurrent with increases in high-latitude moisture and an increase in Eurasian snow cover, which dynamically induces large-scale wintertime cooling.”
But, again, who knows? The only thing that is certain, as Cohen et al. describe it, is that “traditional radiative greenhouse gas theory and coupled climate models forced by increasing greenhouse gases alone cannot account for this seasonal asymmetry.” And so we have yet another reason why so many scientists are so skeptical about the ability of even the most sophisticated of today’s climate models to adequately portray reality.
Can someone explain to me what “traditional radiative greenhouse gas theory” actually means ?
I thought it was that GHGs absorbed IR from the surface and radiated it back to the surface increasing heating of the Earth’s surface as the rest of the atmosphere isn’t capable of absorbing IR and is therefore not a GHG.
Therefore, shouldn’t this phenomenum show up in the experimentally determined physical properties of these gases ?
As far as I can see both 100% CO2 and 100% steam (you can’t get 100% water vapour) have thermal conductivity values wayyyyy less than normal air.
How is it possible for gases to have a claimed heating effect when they are better insulators than most of the biosphere ? (Ok they may act to reduce heat loss from the surface by low thermal conductivity but this is NOT what is claimed – besides they are TRACE gases.)
I know some will think this is stupid because we’re talking radiation – right ?
But how could anyone experimentally determine thermal conductivity that somehow excluded any radiative effect ???
The bottom line Rosco is that GHGs can absorb infrared radiation in wavelengths emitted by earth’s non-gaseous surface. This is not in dispute and is replicable in saturation chamber experiments. This then means that they can be excited by means other than conduction, which is the primary means of heating the atmosphere and thus could increase the rate of warming of the atmosphere or, more correctly, slow its rate of cooling.
None of this is contentious. Nor is it contentious that the atmosphere (not just GHGs) emits radiation in longwave and that some of this is absorbed by the non-gaseous surface. You can see time series data on downwelling longwave radiation (or downwelling longwave flux as it is frequently called DLR/DLF) from the World Radiation Monitoring Center – Baseline Surface Radiation Network (WRMC-BSRN) or simply check out a paper by Pavlakis et al where they’ve bothered to compute the 10-year averages, coming up with just over 340 W/m2.
Where it becomes contentious are claims that the small atmospheric warming available through increased CO2 will enable the atmosphere to hold more water vapor and simultaneously increase the supply of water vapor through increased evaporation – both occurrences which are intuitively and physically reasonable. What is not reasonable is the expectation that this will occur in isolation without incurring negative feedbacks such as increased cloud formation and albedo, increased lofting via auto-convection bypassing enhanced greenhouse effect or simple lack of available energy in appropriate wavelengths to increase net effect.
Then there’s the question of just how sensitive the system is to perturbation altering non-gaseous surface temperature.
Hopefully this covers what you are after.