Please support this Forum and Neven's Blog

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - josh-j

Pages: [1]
1
Eric's latest and probably last comment on the Stoat blog also confuses matters further, because first he dismisses Rob's critical analysis as "nonsense", but then he takes his time to repeat that "we assume, in effect, that most of the trend in Z200 is "natural variability"."

Which is exactly the assumption that many here have expressed serious doubts about.
(emphasis mine)

I think it is worth taking the bolded section above in context:

: Eric Stein
There is one aspect that might be worth discussing, which is that we assume, in effect, that most of the the trend in z200 is “natural variability”. (We don’t actually assume it — that’s a result of the analysis, but in the end it amounts to the same thing, pretty much). But this doesn’t come out of nowhere! it comes largely from our previous work published in 2014, showing that the trend in z200 is related to tropical forcing.

The 2014 paper is, I believe, the following:

Ding, Q. H. et al. Tropical forcing of the recent rapid Arctic warming in northeastern Canada and Greenland. Nature 509, 209-212 (2014).

From the abstract:
Here we show that the recent warming in this region is strongly associated with a negative trend in the North Atlantic Oscillation, which is a response to anomalous Rossby wave-train activity originating in the tropical Pacific. Atmospheric model experiments forced by prescribed tropical sea surface temperatures simulate the observed circulation changes and associated tropospheric and surface warming over northeastern Canada and Greenland. Experiments from the Coupled Model Intercomparison Project Phase 5 (ref. 16) models with prescribed anthropogenic forcing show no similar circulation changes related to the North Atlantic Oscillation or associated tropospheric warming. This suggests that a substantial portion of recent warming in the northeastern Canada and Greenland sector of the Arctic arises from unforced natural variability.

I think if we have doubts about an assumption of natural variability in Z200 (I have no idea myself), it might worth looking at this paper, not just the 2017 one. I could not find it at a glance outside of the paid Nature publication however.

2
If I am reading the original graph correctly, it is not indicating a slowdown at all.

This is easy to misinterpret because it shows the anomaly on a yearly basis, which is still increasing.

So, while there appears to have been a sharper year-on-year increase previously, we are still at the maximum per year change.

Even if the graph were to completely flatten out, we would still be dropping per year at the maximum observed rate of ~ 750 k km^2

If you're referring to Tamino's graph, I think it is showing the cumulative anomaly, not the rate of change. So an anomaly of -1 would mean 1 less than normal. not a rate of change of -1 per unit of time.

3
The forum / Re: Neven's "TIP JAR"
« on: March 08, 2017, 11:48:46 PM »
Thanks for all your hard work Neven - all the ASIs (ASIF, ASIB and ASIG) are great resources and I check this forum daily so its probably about time I paid my dues. :)

4
The rest / Re: 2017 open thread
« on: March 02, 2017, 02:49:04 PM »
Cid, I will choose to live my life in such a way that I can die with the satisfaction of knowing I tried all I could to prevent or limit a terrible catastrophe and with hope for the goodness of human nature.

If we fail then so be it. But to go to the grave having done sod all to attempt to limit such a disaster as we are facing is a terrible thought to my mind. Even if it were clear that this is inevitable (I do not think it is really even possible to know that at this point, even though the prospects aren't great), I would still gain far more satisfaction in my life from actually trying to do something about it anyway, and die happier knowing I represented the final burning flame of human optimism for all that we love.

I do not wish to go quietly into the night

5
The rest / Re: 2017 open thread
« on: March 01, 2017, 01:07:58 AM »
Nevertheless 5to10 is right; giving up on the assumption that nothing will work misses the potential we humans have to act differently.

Collective action won't come about through data alone. People need to grasp the issue emotionally and also be able to see a way forward so as to be moved to action rather than denial or despair. It's something I expect many posters here have experienced; the feeling of knowing what is coming while also continuing 'normal' life.

But if 'our' knowledge was more widely understood, this despair aspect would drop away and be replaced with hope. Even if we couldn't ultimately succeed, we would be part of a heroic effort, and I think that is a common trait that could be awoken in most people.

As to how this could be done... I wonder how constrained reporters are by their rich media-mogul bosses?

This is a great discussion - and 5to10, you certainly woke me up just now (right before bed  ;D )

6
Arctic sea ice / Re: Arctic temperature layers and inversions
« on: February 23, 2017, 07:11:35 PM »
@crandles
I am still working toward understanding this better myself. I believe what is being said is that as the lower level heats and reverses the initial inversion, then a positive feedback is started and the heat is radiated downward after that point, instead of cooling into space.

My reading of the paper is that the inversion is a positive factor in surface warming amplification. Therefore to my mind, once the inversion is lost the amplification could reduce.

As the paper says:

"The ability of the Arctic wintertime clear-sky atmosphere to cool to space decreases with inversion strength."

Of course there are many more than this single factor in Arctic warming amplification and clearly the ongoing (?) weakening of the inversion is not saving the Arctic so far. But my non-expert reading is that at least for this one specific feedback, increased warming might actually reduce the feedback as the inversion strength weakens.

I'd be curious to know the thoughts of you intelligent people on this.  :)

7
Arctic sea ice / Re: Arctic temperature layers and inversions
« on: February 19, 2017, 12:26:33 AM »
Well we are already experiencing the first consequences of the ground-level warming surely. The next question is how a lack of inversion would affect atmospheric dynamics. Note one of Aslan's earlier links (http://www.nature.com/ngeo/journal/v4/n11/full/ngeo1285.html) which suggests the temperature inversion had an amplifying effect on warming - could that amplification be lost?

Even if so, I suppose it is replaced by warming from the increased atmospheric moisture content. But these are just idle musings (I have no knowledge but am trying to learn).

I am particularly interested in whether the loss of inversion itself (rather than just the temperature rise) would have effects on weather patterns locally and more widely in the winter..?

Thanks for this Aslan.

8
Arctic sea ice / Re: Stupid Questions :o
« on: February 18, 2017, 11:10:24 PM »
Thank you very much Crandles, much obliged! And thanks to Jim also. :)

9
Arctic sea ice / Re: Stupid Questions :o
« on: February 18, 2017, 05:22:56 PM »
Here is my stupid question:

DMI 80n graph page says the data is derived from the ECMWF operational model. I can see in the older graph years that ERA40 was used but I don't know what the "operational model" is now.

Basically I want to get the data behind the DMI 80N graph but am struggling to find out where to look. I'm not sure if the values calculated by DMI are available somewhere but cannot see anywhere to obtain from their site?

Thanks for any help :)

10
Arctic sea ice / Re: 2017 sea ice area and extent data
« on: February 16, 2017, 09:04:40 PM »
When I look at the DMI 80N since the beginning of 2016 I count 9 bricks.  The bottom temp simply has not been able to break through 247 in 9 tries.

Indeed DMI 80N has not dropped below the green line (in winter) since December 2015. :o

I can't see any year other than 2016 that has the property of being always above average in DMI 80N (well, there is also 2017 so far..). However I don't have the knowledge to make my speculation worth much if I was to start predicting next winter!

11
Arctic sea ice / Re: What the Buoys are telling
« on: February 14, 2017, 06:54:57 PM »
A hearty "welcome back" to OBuoy 14, and thank you to everyone for their interesting posts in this thread. I followed 14's journey through the melt season and was sad when it finally turned off.

Well done to the buoy for making it through, and to whoever was involved in constructing these buoys.  :)

12
Science / Re: Scientists scramble to safeguard data ahead of 'scrubbers'
« on: December 16, 2016, 05:13:51 PM »
Hopefully on-topic enough - certainly a good counter to the (justifiably, IMO) rather doom-laden original post:

Jerry Brown strikes defiant tone: ‘California will launch its own damn satellite’


Gov. Jerry Brown, rallying a room of scientists Wednesday with his most heated rhetoric yet on the topic, suggested California would defy the federal government should President-elect Donald Trump impede the state’s efforts to thwart climate change.

He said if the federal government “starts messing with” the state’s renowned science facilities, such as Lawrence Livermore National Laboratory, “I am the president of the Board of Regents. I am going to say, ‘Keep your hands off. That laboratory is going to pursue good science.’ ”


The speech is available on YouTube here (and is firey stuff):

https://www.youtube.com/watch?v=kWSgncpqWtE


[Thanks to Neven and all who contribute here for such an enlightening forum  :)]

Pages: [1]