On the Environmental Defense Fund website, this claim is made:

This past winter’s polar vortex episode was caused by a persistent high pressure system that developed over western Canada, which pushed the jet stream southward.

The current summertime polar vortex episode is caused by the Super Typhoon Neoguri that hit Japan last week, which has dramatically altered the jet stream (and also created a high pressure system over western Canada).

The connection to climate change

Both of these triggers—a persistent high pressure system and a strong storm —are consistent with climate change projections by experts. Even a weaker jet stream in general is anticipated as sea ice melts in the Arctic.

"climate change projections" is linked to a page with this image:

enter image description here

Is it true that a warming planet causes colder temperatures?


1 Answer 1


The question posed in here "Is it true that a warming planet causes colder temperatures?" is a non-sequitur, following as it does a discussion of changes in patterns of precipitation (in this case snow), rather than temperature.

The article referenced is clearly discussing changes in extreme weather (short term) resulting from climate change (in this case affecting the jetstream). These sot or changes (increases) in extreme weather are indeed discussed in the IPCC reports. See e.g. chapter 11 of the IPCC AR4 WG1 report.

Extremes: There has been a large increase in the available analyses of changes in extremes. This allows for a more comprehensive assessment for most regions. The general findings are in line with the assessment made in TAR and now have a higher level of confidence derived from multiple sources of information. The most notable improvements in confidence relate to the regional statements concerning heat waves, heavy precipitation and droughts. Despite these advances, specific analyses of models are not available for some regions, which is reflected in the robust statements on extremes. In particular, projections concerning extreme events in the tropics remain uncertain. The difficulty in projecting the distribution of tropical cyclones adds to this uncertainty. Changes in extra-tropical cyclones are dependent on details of regional atmospheric circulation response, some of which remain uncertain.

Compare this with straw man "one side claims all data and predictions are perfectly without fault" (c.f. comment by the OP above). Note that even here in the summary, the IPCC are being very careful to state defficiencies in the modelling work available and the uncertainties. I strongly recommend people obtain a copy of the IPCC report and read that, rather than climate skeptic blogs.

As to polar vortex, the models do predict there will be changes in its behaviour as a result of climate change:

Interannual variability over North America is connected to two large-scale oscillation patterns (see Chapter 3), ENSO and the NAO/AO. The MMD model projections indicate an intensification of the polar vortex and many models project a decrease in the arctic surface pressure, which contributes to an increase in the AO/NAO index; the uncertainty is large, however, due to the diverse responses of AOGCMs in simulating the Aleutian Low (Chapter 10). The MMD model projections indicate a shift towards mean El-Niño like conditions, with the eastern Pacific warming more than the western Pacific; there is a wide range of behaviour among the current models, with no clear indication of possible changes in the amplitude or period of El Niño (Chapter 10).

Again, unlike the climate change dissenters' caricature of the debate, note the clear statement of the uncertainties.

From the most recent AR5 WGI report

Anthropogenic climate change may also bring systematic cold-season precipitation changes. As with previous models, CMIP5 projections generally agree in projecting a winter precipitation increase over the northern half of NA (Figure 14.18 and AI.19). This is associated with increased atmospheric moisture, increased moisture convergence, and a poleward shift in ETC activity (Section 14.6.2 and Table 14.3). The change is consistent with CMIP3 model projections of positive NAO trends (Table 14.3; Hori et al., 2007; Karpechko, 2010; Zhu and Wang, 2010). Winter precipitation increases extend southward into the USA (northern portions of SREX regions 3 to 5; Neelin et al., 2013) but with decreasing strength relative to natural variability. This behaviour is qualitatively reproduced in higher resolution simulations (Figure 14.18).

  • @oddthinking, the straw man "one side claims all data and predictions are perfectly without fault" was made by Gracchus in the comments to the original question. It makes no sense not to identify him as the source of that straw man as he raised it in connection to what is his question.
    – user18604
    Jul 17, 2014 at 9:55
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    As for removing direct references to Gracchus in the answer: it's a tough one. When I read the answer initially, I thought it read like an attack on an individual, rather than a general answer that will stand long after the individuals involved in asking, answering and moderating have moved on. [Waves to the people reading this a decade from now!]
    – Oddthinking
    Jul 17, 2014 at 11:59
  • Just to be clear: there will be blizzards in the same geographic areas as glaciers or even warmer zones? Don't blame me because the linked site used that picture as a "climate change projection".
    – user20862
    Jul 17, 2014 at 13:45
  • Gracchus, you are missing the point. The presence of blizzards does not imply that it is necessarily colder than usual for the time of year, as the difference may be due to additional precipitable moisture in the atmosphere. That is exactly what the illustration depicts, with winds picking up moisture from open water "increased moisture in atmosphere". I have already explained why glaciers are not likely to be affected by the same sort of issues that give rise to extreme events such as blizzards, but to the long term average temperature.
    – user18604
    Jul 17, 2014 at 14:04
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    I don't think the article is suggesting that, it is worth noting that the article talks about "polar-vortex-in-the-mid-latitude situations", i.e. Arctic weather where weather wouldn't normally be expected/common. The ice melting mentioned is specifically in the Arctic "Even a weaker jet stream in general is anticipated as sea ice melts in the Arctic.". So the article is not suggesting there will be blizzards and ice melting at the same place at the same time. This suggests that it is the melting of the Arctic sea ice that is thought to be destabilising the polar vortex.
    – user18604
    Jul 21, 2014 at 17:46

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