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Learning Global Warming facts and fiction

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Thanks very much for the recommendation of caution, Eric, when using ERA-40 for the daily climo normals. I will do so. I do see a similar day to day pattern of changes in anomalies. Regardless, I clearly see discrepancies in the anomalies when comparing the two datasets for a particular day. For example, consider the period 9/1/16-4/30/17:

whereas the ERA-40 base shows not even a single day colder than normal, the JRA-55 data shows there were about 28 days colder than normal. This actually suggests a couple of degree C WARM rather than cold bias for the ERA-40 based daily anomalies vs the anomalies shown in JRA-55 mainly in DJF. The other months look pretty close. May looks pretty close up until just the last 3 or so days as both were mainly 1 to 3 C colder than normal for May up til then. So, even your link's data suggests May has been chilly in the Arctic most of the month. However, there clearly is a difference now. So, I agree that caution is needed.

Aside: I had already noted earlier in this thread that I do have a concern about the 10 or so years having a disconnect of 7C+ between 12/31 of one year and 1/1 of the subsequent year as regards actuals. That still doesn't make sense.
 
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Webberweather53 said:
I definitely would be cautious in utilizing the DMI Arctic temperatures, ERA-40 that's used for the climatological period is noted to have spurious trends in the arctic esp below the mid troposphere, henceforth it's climatological base period is also likely in error... JRA-55 daily temperatures are significantly warmer and are actually running about 1C above average poleward of 80N.

View attachment 565

See this short paper by Screen and Simmonds (2010) "Erroneous Arctic Temperature Trends in the ERA-40 Reanalysis: A Closer Look"
http://journals.ametsoc.org/doi/pdf/10.1175/2010JCLI4054.1
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I just did a rough estimate of the differences in the average anomalies for the ERA-40 dataset for two periods to compare to what Ryan's graph shows for JRA-55 and came up with this:

- For 10/1/16 to present: whereas the average anomaly for JRA-55 is only +3.38 C, the average anomaly for ERA-40 is ~+6 C.

- For 2017 YTD: whereas the average anomaly for JRA-55 is only +1.69 C, the average anomaly for ERA-40 is ~+4 C.

- So, for both periods, the average anomaly for the JRA-55 is over 2C cooler. That's intuitive because I'm assuming a good portion of this is due to JRA-55/Ryan using 1981-2010 as the base vs ERA-40 using the quite a bit cooler 1958-2002 as its base.
 
GaWx said:
I just did a rough estimate of the differences in the average anomalies for the ERA-40 dataset for two periods to compare to what Ryan's graph shows for JRA-55 and came up with this:

- For 10/1/16 to present: whereas the average anomaly for JRA-55 is only +3.38 C, the average anomaly for ERA-40 is ~+6 C.

- For 2017 YTD: whereas the average anomaly for JRA-55 is only +1.69 C, the average anomaly for ERA-40 is ~+4 C.

- So, for both periods, the average anomaly for the JRA-55 is over 2C cooler. That's intuitive because I'm assuming a good portion of this is due to JRA-55/Ryan using 1981-2010 as the base vs ERA-40 using the quite a bit cooler 1958-2002 as its base.
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Yea that's right, on the other hand, the biases noted by Screen and Simmonds (2010) were regarding ERA-40's profound warm bias esp later in the 1990s when alterations were made regarding the input of satellite radiance measurements... In addition, JRA-55 is actually running warmer than the ECMWF (operational) vs the ERA-40 1958-2002 climatological base period atm
 
GaWx said:
Aside: I had already noted earlier in this thread that I do have a concern about the 10 or so years having a disconnect of 7C+ between 12/31 of one year and 1/1 of the subsequent year as regards actuals. That still doesn't make sense.
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I had written to those that run the website that has this daily Arctic temperature graph and got this answer this morning (they left off days 361-365 through 2008...so the last day of the year showing on the graph through 2008 was 12/26 (or 12/25 in leap years) meaning a jump from 12/26 of one year to 1/1 of the subsequent year):

"Hi Larry

Thanks for your question - well spotted! :)

The thing is that plots before 2009 only show data from day 1 to day 360 (by a rather dumb mistake), thus leaving the last 5 days of the year out of the plot!! From 2009 this has been corrected.

I simply haven't found the time to re-plot the time series...

Cheers"

http://ocean.dmi.dk/arctic/meant80n.uk.php
 
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After a colder than average Arctic May helped slow Arctic ice-melt down in May to less than the faster ice-melt rates of recent Mays, June has warmed to near normal, thus leading to a steeper ice melt rate over the last week or so:

Arctic daily temperatures:
http://ocean.dmi.dk/arctic/meant80n.uk.php

This has gotten 2017 back to 2nd lowest Arctic ice extent on record for the date behind only 2016. Because of the record warm Arctic fall/winter, we're skating on thin ice so to speak. So, it will be crucial to get back to a colder than normal Arctic this summer to avoid what could easily end up as the lowest ice extent minimum on record come September. Current lowest is 2012.

Arctic ice extent:

http://web.nersc.no/WebData/arctic-roos.org/observation/ssmi_ice_ext.png
 
GaWx said:
After a colder than average Arctic May helped slow Arctic ice-melt down in May to less than the faster ice-melt rates of recent Mays, June has warmed to near normal, thus leading to a steeper ice melt rate over the last week or so:

Arctic daily temperatures:
http://ocean.dmi.dk/arctic/meant80n.uk.php

This has gotten 2017 back to 2nd lowest Arctic ice extent on record for the date behind only 2016. Because of the record warm Arctic fall/winter, we're skating on thin ice so to speak. So, it will be crucial to get back to a colder than normal Arctic this summer to avoid what could easily end up as the lowest ice extent minimum on record come September. Current lowest is 2012.

Arctic ice extent:

http://web.nersc.no/WebData/arctic-roos.org/observation/ssmi_ice_ext.png
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Like the post, not the "news" ... ;) and :(
 
Here is an interesting write up from way back in 2004, which claimed that 1940-2000 was the most active 60 years for the sun (more sunspots, flux, etc) of the past 8000 years based on the levels of C-14 found in the tree rings of ancient tree trunks:

https://www.mpg.de/research/sun-activity-high

The significance of this supposed most active solar period in 8000 years is that it brings up the POSSIBILITY that a significant portion of global warming since the mid 20th century was actually a result of the very active sun since 1940. With the sun's overall activity now plunging and with a forecast of the weakest sunspot cycle in at least 200 years quite possibly followed by several more very weak cycles, there is a chance for global temperatures to reverse downward to a significant degree over the next few decades once any possible lag in global warming resulting from this very active 1940-2000 solar period has finally been fully incorporated.

I have for several years known about that period being the most active for the sun over the last 400++ years based on the well known sunspot records. Then I learned just this past February that it was quite possibly the most active in 2000 years as per this post I made in this thread:

http://southernwx.com/community/threads/global-warming-facts-and-fiction.85/page-3#post-20435

Today, I discovered it may very well have been the most active 50 years of the last 8000.
 
The direct forcing from solar irradiance is on the order of a few magnitudes less than most other parameters in the climate system and only varies about 0.1% over the course of a solar cycle, not to mention variations in solar activity wrt large-scale climate phenomena are still very elusive at best...
 
^ The variation of the DIRECT forcing from solar irradiance within a solar cycle (11 years on average) has been determined to be small, thus leading to global temperature variations of less than 0.1C. So, there's no debate there. However, there has been a lot written since 1997 about the POSSIBILITY that indirect effects of solar output variations due to things like the variation in the level of cosmic rays (CR) reaching our planet are much greater. There's been a lot of debate about the relative significance of this factor. The idea for those who don't know it is that decreased solar radiation allows for more CR to reach Earth. Supposedly, the average variation of CR reaching Earth within a cycle is near 15%. This supposedly leads to increased nuclei that lead to increased low cloud-cover, which then cools the globe. The big debate is the level of cooling this could cause as well as whether or not multiple weak solar cycles during a grand minimum would enhance this cooling due to a cumulative effect. Here is a link that explains the solar output-CR connection and the POSSIBILITY of it being a significant factor on global temperatures:

http://planet.botany.uwc.ac.za/NISL...e/Verification/N Shaviv/Responses/Carslaw.htm
 
GaWx said:
^ The variation of the DIRECT forcing from solar irradiance within a solar cycle (11 years on average) has been determined to be small, thus leading to global temperature variations of less than 0.1C. So, there's no debate there. However, there has been a lot written since 1997 about the POSSIBILITY that indirect effects of solar output variations due to things like the variation in the level of cosmic rays (CR) reaching our planet are much greater. There's been a lot of debate about the relative significance of this factor. The idea for those who don't know it is that decreased solar radiation allows for more CR to reach Earth. Supposedly, the average variation of CR reaching Earth within a cycle is near 15%. This supposedly leads to increased nuclei that lead to increased low cloud-cover, which then cools the globe. The big debate is the level of cooling this could cause as well as whether or not multiple weak solar cycles during a grand minimum would enhance this cooling due to a cumulative effect. Here is a link that explains the solar output-CR connection and the POSSIBILITY of it being a significant factor on global temperatures:

http://planet.botany.uwc.ac.za/NISL/Gwen's Files/GeoCourse/Climate Change/Verification/N Shaviv/Responses/Carslaw.htm
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Yes I'm more than aware of this, they're an innumerable amount of indirect agents that have some impact on the climate that ultimately are derived from the sun and I've mentioned a few of those on this very forum. However, there's very little, if any confidence in any of these agents and what impact, if significant at all they have and to make some of the assertions you've made above wrt decreasing global temperatures in the coming decades due to lower solar activity, which again is far too elusive atm to have much faith in whatsoever... GCRs modulate cloud condensation nuclei (aerosols in particular) which must generally grow by a factor of about 10^6 to begin scattering incoming solar radiation, and it's been well established that GCRs can modulate CCN, however, CCN's impact on the climate system is elusive, even more so than solar irradiance because many of the processes are of second order and involve microphysical forcing-feedback-response interactions with clouds, which have uncertainty ranges that are nearly equivalent to the forcing of ALL other anthropogenic forcing agents, combined...
 
^ Eric, you mentioned when referring to me "assertions you've made above wrt decreasing global temperatures in the coming decades due to lower solar activity".

I think that using the word "assertions" is not accurate. I'd replace what you said with "speculation about the possibility of decreasing global temperatures in the coming decades due to lower solar activity". Note that I used the words "chance" and "possibility" when referring to any cooldown over the next few decades from reduced solar activity. I'm not asserting but I am speculating about the possibility.
 
GaWx said:
^ Eric, you mentioned when referring to me "assertions you've made above wrt decreasing global temperatures in the coming decades due to lower solar activity".

I think that using the word "assertions" is not accurate. I'd replace what you said with "speculation about the possibility of decreasing global temperatures in the coming decades due to lower solar activity". Note that I used the words "chance" and "possibility" when referring to any cooldown over the next few decades from reduced solar activity. I'm not asserting but I am speculating about the possibility.
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Even still, it's probably not worth speculating about that possibility given the exceptionally large uncertainty bars and host of other factors that are liable to continue inducing more than enough forcing to completely mask the impacts of decreasing solar activity and result in continued warming...
 
Webberweather53 said:
Even still, it's probably not worth speculating about that possibility given the exceptionally large uncertainty bars and host of other factors that are liable to continue inducing more than enough forcing to completely mask the impacts of decreasing solar activity and result in continued warming...
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You said "liable to continue inducing more than enough forcing to completely mask the impacts the impacts of decreasing solar radiation and result in continued warming". Of course, the word "liable" suggests merely a likelihood rather than a certainty even in your own mind. So, why isn't it worth speculating about the POSSIBLE significant cooling impact of reduced solar output? Isn't speculation about possibilities when considering overall inherent uncertainty an important part of the scientific discovery process?
 
The Arctic extent has been taking its seasonable sharp dive the last few weeks (see 2017 red line in the linked graph):

http://web.nersc.no/WebData/arctic-roos.org/observation/ssmi_ice_ext.png

With the extreme warmth of this past fall/winter in the Arctic meaning the ice that is not in good shape, with current extent only barely above the 2012 extent for this date per this graph, and with current Arctic temperatures now rising back to near normal, there is more than a trivial chance that this year's minimum ice extent will go below the 2012 low point. The best hope imo would be a return to a chilly pattern up there later this summer like was the case in most of May.
 
GaWx said:
You said "liable to continue inducing more than enough forcing to completely mask the impacts the impacts of decreasing solar radiation and result in continued warming". Of course, the word "liable" suggests merely a likelihood rather than a certainty even in your own mind. So, why isn't it worth speculating about the POSSIBLE significant cooling impact of reduced solar output? Isn't speculation about possibilities when considering overall inherent uncertainty an important part of the scientific discovery process?
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Yes it's possible, anyone would agree that the odds aren't zero, just that is your proposition actually legitimate and backed by a large, extensive body of literature? The answer is definitely no and what you've said above is just mere unquantifiable conjecture that's unlikely to verify given the relatively smaller forcing variance attributable to solar activity on multideacadal-centennial temporal scales in comparison to the cumulative impact of anthropogenic GHGs, aerosols, and feedbacks onto the ocean and atmosphere...
 
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