Cold snaps like the ones that hit the eastern United States in the past winters are not a consequence of climate change. Scientists at ETH Zurich and the California Institute of Technology have shown that global warming actually tends to reduce temperature variability.
Repeated cold snaps led to temperatures far below freezing across the eastern United States in the past two winters. Parts of the Niagara Falls froze, and ice floes formed on Lake Michigan. Such low temperatures had become rare in recent years. Pictures of icy, snow-covered cities made their way around the world, raising the question of whether climate change could be responsible for these extreme events.
It has been argued that the amplified warming of the Arctic relative to lower latitudes in recent decades has weakened the polar jet stream, a strong wind current several kilometres high in the atmosphere driven by temperature differences between the warm tropics and cold polar regions. One hypothesis is that a weaker jet stream may become more wavy, leading to greater fluctuations in temperature in mid-latitudes. Through a wavier jet stream, it has been suggested, amplified Arctic warming may have contributed to the cold snaps that hit the eastern United States.
Temperature range will decrease
Scientists at ETH Zurich and at the California Institute of Technology, led by Tapio Schneider, professor of climate dynamics at ETH Zurich, have come to a different conclusion. They used climate simulations and theoretical arguments to show that in most places, the range of temperature fluctuations will decrease as the climate warms. So not only will cold snaps become rarer simply because the climate is warming. Additionally, their frequency will be reduced because fluctuations about the warming mean temperature also become smaller, the scientists wrote in the latest issue of the Journal of Climate.
The study’s point of departure was that higher latitudes are indeed warming faster than lower ones, which means that the temperature difference between the equator and the poles is decreasing. Imagine for a moment that this temperature difference no longer exists. This would mean that air masses would have the same temperature, regardless of whether they flow from the south or north. In theory there would no longer be any temperature variability. Such an extreme scenario will not occur, but it illustrates the scientists’ theoretical approach.
Extremes will become rarer
Using a highly simplified climate model, they examined various climate scenarios to verify their theory. It showed that the temperature variability in mid-latitudes indeed decreases as the temperature difference between the poles and the equator diminishes. Climate model simulations by the Intergovernmental Panel on Climate Change (IPCC) showed similar results: as the climate warms, temperature differences in mid-latitudes decrease, and so does temperature variability, especially in winter.
Temperature extremes will therefore become rarer as this variability is reduced. But this does not mean there will be no temperature extremes in the future. “Despite lower temperature variance, there will be more extreme warm periods in the future because the Earth is warming,” says Schneider. The researchers limited their work to temperature trends. Other extreme events, such as storms with heavy rain or snowfall, can still become more common as the climate warms, as other studies have shown.
North-south shift makes the difference
And the jet stream? Schneider shrugs off the idea: “The waviness of the jet stream that makes our day-to-day weather does not change much.” Changes in the north-south difference in temperatures play a greater role in modifying temperature variability.
Schneider wants to explore the implications these results have in further studies. In particular, he wants to pursue the question of whether heatwaves in Europe may become more common because the frequency of blocking highs may increase. And he wants to find why these high pressure systems become stationary and how they change with the climate.
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“Using a highly simplified climate model….”
Well that’s already inspired my confidence in the conclusions 🙂
Do we even know what the actual temps across the Poles are? It seems to me they’re both SWAGs based on a very small sample size that is then extrapolated for locations up to 1200km away. How can anyone use such numbers with any kind of confidence?
And, across a singularity region. It’s like trying to predict the direction of the lay of a person’s hair on his crown based on measuring it at his ears, collar, and forehead.
Oh so Marcel Leroux was right after all… But now a model proves it…
Cool photo of all that snow.
Very impressive the way they sweep the state borders so neatly and precisely.
Using a highly simplified climate model, they examined various climate scenarios to verify their theory. It showed that the temperature variability in mid-latitudes indeed decreases as the temperature difference between the poles and the equator diminishes. Climate model simulations by the Intergovernmental Panel on Climate
ABOVE FORM THE ARTICLE ,MY REPLY BELOW. I AM GOING TO SET THE RECORD STRAIGHT.
That is FALSE. When the AO/NAO are in a negative phase which occurs when higher pressure is present over the poles (warm or less cold ) relative to lower pressure over the mid latitudes (cold or less warm) , the atmospheric circulation becomes more meridional (weak polar vortex) which means more extremes in temperature will be present which by the way I will show on my next post the models did not call for.
The models used for evaluating AGW theory originally called for a more zonal atmospheric circulation due to a +NAO/+AO becoming more common in response to increasing greenhouse gases. This equates to colder polar regions relative to the lower latitudes which keep the cold air locked up near the poles.
They have it backwards.
Correct. It is Antarctic sea ice that is the direct proxy for rates of forcing of the climate, it increased in extent since 1995, in the same time frame that Arctic sea ice reduction accelerated.
I should have said half correct as it pertains to the Arctic. They actually have it upside down and not backwards. But the larger problem is in what they have inside out, so called internal variability.
No l don’t think that climate change causes extreme winters.
But l do think that a long term pattern of extreme winters in North America over many years would cause big changes to the climate in the NH.
Because l believe that the trend when North America suffers from a Arctic blast. lt then leads to a mild winter in europe, is just a short term pattern and not a long term trend. The extent of the ice sheets in the last ice age would support this.
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch10s10-3-5-6.html
Ulric had sent this originally. The models forecasted a +AO/+NAO in response to AGW.
Which results in less extremes in the climate.
Below is common knowledge. The argument this article is trying to make under the present variation of temperature contrast between polar regions and the equator is false.
In addition it is prolonged solar minimum activity which causes the ozone distribution /concentrations to change between the poles and lower latitudes that has been correlated with a more meridional jet stream pattern (more extreme weather) not Greenhouse Gases /Low Arctic Sea Ice another false argument being put forth.
“The first type, zonal circulation, is characterised by increasing intensity of the zonal circulation at all latitudes and pole-ward shift of the wind intensity maximums. The circulation is accompanied somewhat by a decrease in the overall range of surface-air temperature between the equator and poles and by an overall increase in the mean global surface-air temperatures. Ocean-surface temperatures tend to increase in high latitudes. The second type, meridional circulation, is characterised by weakening in zonal circulation, shift of the main atmospheric streams toward lower latitudes, and overall decrease in global temperature (Lamb 1972). Both easterly and westerly winds increase during the zonal type of circulation and both decrease in the periods of the meridional type of the circulation.”
Ulric ,you do see where I am coming from with my recent post?
There’s a big problem with that. A more northerly atmospheric circulation in the northern hemisphere has to mean positive AO/NAO, and that cools the AMO, and is directly associated with faster trade winds, which means increases in La Nina conditions and episodes. That lowers the average global surface temperature, like in 1970-71 and 1973-76.
My own analysis of North American climate is that AMO has the greatest effect on eastern CANADA and the northern part of northeastern US which is the area referred to in the above paper for extreme winters . This was confirmed in peer reviewed paper by MULLER ET ALL including JUDITH CURRY called DECADAL TEMPERATURE VARIATIONS , They found less of an impact on Europe . Sometime, the European weather can come directly across from North AMERICA , if one follows the air circulation and when it is colder and the North Atlantic is colder , this may affect Europe( but western Europe mostly)
Now of course with all things being equal the greater the temperature gradient between the pole and equator the more extremes would come about in the mid latitudes , but I do not think that was their point. I think their point (which is wrong ) was if a meridional pattern(-ao/-nao) is superimpose upon a given temperature gradient between the poles and the equator that the lesser variability in the temperature gradient( which comes about with a meridional atmospheric circulation) between the poles and equator would cause less extremes in temperatures in the mid latitudes which is flat out wrong.
If that was their point.
If their point was simply a lesser temperature gradient between the poles and the equator would correlate to less extremes in the mid latitudes then I could see their point.
The temperature gradient in the winter polar vortex depends on the speed of the solar wind. Polar vortex expands and contracts depending on the strength of the solar wind. When expands pressure rises in the troposphere above the the polar circle, which enables the exchange of air at high and mid-latitudes. When the vortex is strong exchange is blocked by a strong jet stream.
ETH Zurich will now be moved to the CAGW banned-list. That is not at all what they wanted to hear about Climate.
Eastern United States? I live in the South and have had three consecutive “extreme” winters. At least compared to previous winters. Dang it’s been cold, and snowy, and icy. It’s cold today in the South. What’s up with that?
Wouldn’t it be better to say CO2 doesn’t cause extreme winters. We should’t succumb to this corruption of language. If climate change is now synonymous with warming, then what words/phrases are we going to use to describe cooling?
The study is evidence that global warming and Arctic Amplification supresses cold outbreaks, at least in the Northern Hemisphere. I hope they do a study for the Southern Hemisphere as well.
A better way to look at a meridional atmospheric circulation versus a zonal atmospheric circulation is extremes will be less with a zonal atmospheric circulation because polar air is locked up near the poles.
How this translates to global temperature averages is complicated because of snow cover changes and cloud cover changes associated with each circulation which could oppose or counter ENSO /AMO phases, associated with each circulation.
I just found out that carbon dioxide acts as a greenhouse gas, trapping extra heat in the atmosphere. Apparently, there is a lot more carbon dioxide in the air than there used to be 100 years ago.
Is this something to worry about?
http://www.fao.org/docrep/005/Y2787E/y2787e03a.htm#FiguraA
The data shows temperatures have risen with a zonal atmospheric circulation and have fallen when the atmospheric circulation is more meridional.
That is because zonality is less cloudy than meridionality due to shorter lines of air mass mixing around the globe.
That observation supports my new climate model rather than the Svensmark hypothesis unless cosmic rays can be shown to influence zonality / meridionality but I don’t see how they could.
It has to be a matter of altering the gradient of tropopause height between equator and poles by altering the ozone creation/destruction processes in the stratosphere differently above equator and poles as per my hypothesis.
Somebody tell that WH idiot Holdren.
Exactly Steve.
Here’s another perspective: he one of war’s influence over climate, leading to extreme winters, such was the case of 1939/1940 winter: http://www.1ocean-1climate.com/193940.php. I recommend you this article, it’s very well documented.
Study: Climate Change causes extreme agendas- details at 11 🙂