Comments on: Twin Cities Experiences Mini-Boulder: #WeatherWhiplash

By: With Global Warming, Will Cold Outbreaks Be Less Common? – Greg Laden's Blog

Wed, 01 Apr 2015 17:48:10 +0000

[…] into the US Northeast a few years ago. And that flood in Boulder, and the flood in Calgary, and the June Of All Rain here in Minnesota last year, and so on. This is the main global warming caused change in weather […]

By: Greg Laden

Greg Laden — Thu, 10 Oct 2013 22:15:23 +0000

I’m sure there will be such a study, I think it is being worked on. Meanwhile we have this:

Petoukhov, V., Rahmstorf, S., Petri, S., & Schellnhuber, H. (2013). Quasiresonant amplification of planetary waves and recent Northern Hemisphere weather extremes Proceedings of the National Academy of Sciences, 110 (14), 5336-5341 DOI: 10.1073/pnas.1222000110

which I summarize here:

http://scienceblogs.com/gregladen/2013/06/04/linking-weather-extremes-to-global-warming/

and here:

http://scienceblogs.com/gregladen/2013/09/28/global-warming-and-extreme-weather-climate-agw/

It is quite possible that there are periods of more curvy jets, and you may be on to something. But you can’t ignore the physics. Arctic Amplification is a thing, and it seems to have a cause (AGW) and an effect (Rossby waves being more common).

By: AJ

AJ — Thu, 10 Oct 2013 14:38:12 +0000

Indeed the chances that an amateur finds a spurious signal is greater than would a pro, so I won’t state that what I found is the gospel. In this case, however, there seems to be corroborating evidence.
I performed a separate computation of NH summertime land temperature variability from 1900 to present using GISTEMP data. This was similar to Dr. Hansen’s probability density plots published last year, except my line plots were of standard deviation for all 11yr rolling periods. My plot showed the same as Dr. Hansen’s for the 1950-present periods; lowest variability in the 1960’s, highest in the present. However, my extended plots showed the early 20th century variability was similar to the present. I also limited my computations to those grid cells reporting at both the beginning and end of the periods and the same pattern was found.
So until a profession study is done dating back to 1900, I’ll stick to my opinion. The new normal in weather variability looks a lot like the old normal. Hopefully a professional study will be performed in the not so distant future. Science must hate a vacuum. Maybe the IPCC community can prioritize this?

By: Greg Laden

Greg Laden — Wed, 09 Oct 2013 18:59:11 +0000

” Just an amateur computation with potentially lots of uncontrolled variables and resulting biases.”

Indeed.

By: AJ

AJ — Wed, 09 Oct 2013 16:05:59 +0000

I’m not sure if speeding up the IPCC process is the answer. To me the answer is to wait decades to see if observations match predictions. Climate science by it’s very nature appears to be science in slow motion.
Sometimes a 30yr signal will disappear if you go back far enough. For example, using the 20th Century Reanalysis V2 U-wind and V-wind datasets, I calculated the average yearly heading of the winds between 40N and 50N. The recent headings have become more meridional compared to the 1960’s, but are similar to the early 20th century. Just an amateur computation with potentially lots of uncontrolled variables and resulting biases. I still think it would be a challenge though for a professional to falsify the hypothesis that today’s Rossby waves are similar to those in the early 20th century.

By: Greg Laden

Greg Laden — Tue, 08 Oct 2013 21:39:33 +0000

That’s one of the reasons we are asking the IPCC process to be sped up. The AA-jet stream effects are very recent (in their frequency). There isn’t any argument that they are not real, and are not the reason for the wacky weather. There is a very good argument that AA causes the Rossby waves. We know for certain that the AA is caused by sea ice collapse and decrease in snow and ice cover, and we know this is caused by AGW.

By: AJ

AJ — Tue, 08 Oct 2013 13:42:37 +0000

New normal?

http://rogerpielkejr.blogspot.ca/2013/10/coverage-of-extreme-events-in-ipcc-ar5.html

“… key statements from the IPCC AR5 WGI Chapter 2 on extremes”

“Precipitation extremes also appear to be increasing, but there is large spatial variability”

“In summary, there continues to be a lack of evidence and thus low confidence regarding the sign of trend in the magnitude and/or frequency of floods on a global scale.”

By: Eric

Eric — Sun, 06 Oct 2013 01:28:49 +0000

In 2007, Winona was nailed by over a foot of rain within 24 hours. The exrtreme is becoming normal.