Thanks for the discussion Jeff. Apologize if my initial post came off as grumpy... I'm pretty passionate about the fishery and I think these things are critically important to the future management of our fishery and worthy of discussion, so just dismissing them out of hand gets me a bit fired up. To your last point about not having time to research all the stuff and having professionals... that is what makes it even more frustrating to see a lack of trust in experts. I'll admit up front I am not a climate modeler or expert in abiotic factors. I'm a fish manager. I don't always have the answers and I try to be up front when I'm not a subject expert. But the folks that are doing the climate models and fish production are very, very smart people when it comes to that and I think it's important to take what they say seriously and in good faith. Even those experts acknowledge in their papers and reports that there are many, many uncertainties relating to how climate change will affect biological, chemical, and physical habitat of systems as large as the great lakes. There is so much we don't know about current conditions that stacking future change on top of that makes it very hard to know what comes in the future.
Your questions, which are great:
1) I think it's always very difficult to write about science for the general public without simplifying it, and that's even if you aren't trying to sell papers. That's why it's really important to go read the actual reports and talk to the experts behind the report, rather than just reading the newspaper article. Trust me, natural resource professionals are often frustrated by the end product of a newspaper article or a radio or TV spot. Most people don't care about complexity and nuance, and all the important details are often left out by the time things show up in public. It's extra work, but to be an informed citizen, unfortunately it does take a little more than reading a headline or an article, or reposting a facebook meme at the low end of the spectrum.
3) Yes... the weather is erratic and there are large variations in the short term. Lake Michigan is especially complicated because of thermal stratification and upwellings, which add another layer of complexity when it comes to historical temperature measurements. I don't know what widespread and verified data on things such as ice cover and average lakewide surface temperature exist prior to the "modern" era of science and management, (say 1960s onward) to be honest. It probably exists as a model somewhere given air temperature records, which are much more widespread and go back much, much much further. NOAA is likely the best place for that, and you can see most of their comprehensive data goes back to the 60s and 70s
www.glerl.noaa.gov/data/ice/#historical. Surface temperature data back to 1995 is available here
coastwatch.glerl.noaa.gov/statistic/
Many things that are critically important to evaluating thermal habitat (i.e. temperature profiles) have very little historical data, since the technology and funding for buoys like the Michigan City Sea Grant buoy with temperature strings did not exist prior to a decade or so ago. Satellite remote sensing of surface temperatures is also a fairly recent technology that is widespread now.
4) Kao's paper states it is using 1964-1993 as a baseline, and comparing to the projections for the 2040s-2070s. Surface temps have been increasing about 1 degree per decade since the 60s I believe, according to various literature cited. So we're a couple degrees warmer (on average) compared to the 60s-early 90s average. The actual raw data/charts are hard to find in studies examining the effect of temperature on fish, because they are typically in a model somewhere, and they are a data input, not an output. I put the GLERL data from 1995-2017 into Excel and the trendline for average Lake Michigan yearly surface temperature (averaged across every single day) has increased about a 1.5 degrees since 1995. The trendline slope is about .07 degrees per year, or 0.7 degrees per decade since 1995.
5) Yes, half optimistic and half pessimistic might be a good way to put it. Changes don't occur in a vacuum, and what is good for one species might not be good for others. Wisconsin for example has measured an increase in largemouth bass in many of their northern lakes, which they believe is a result in warmer water temperature and vegetation growth, and a decrease in walleye. Good for bass anglers, not so much for walleye anglers. There has been some research that shows weak correlations of ice cover and alewife, and reduced overwinter mortality in warmer winters... but the biggest determinant (historically) for alewife yearclass strength was the chinook yearclass strength of the same cohort. IE the more baby kings = fewer baby alewives. Warmer temperatures and increased precipitation and runoff in the lake could mean more primary productivity available for alewife, which would be good... but could also mean that metabolisms of predators is higher due to the increased temps, leading to increased consumption demand, which might or might not offset any potential increase in productivity.
In terms of recruitment, that's where much of the uncertainty comes in. For example, just from an abiotic standpoint (ice cover, water temp, winds etc) it might be expected that whitefish recruitment should increase decades in the future. This paper thinks so:
www.researchgate.net/publication/2678983...chigan_and_Superior_. However... biotic factors also play a huge role. We're seeing declining whitefish recruitment in the northern part of the lake, and there is an effort starting to try to figure out why. It's likely tied to changes in the food web cascading from the bottom up (mussels). Sea lamprey mortality has been shown to increase as water temperatures warm, and lampreys in Lake Superior have gotten bigger and more fecund (reproductively viable) as water temps have warmed. So that could be an issue as well.
Another factor apart from average yearly water temp is the specific timing of warm ups in the spring and cool-downs in the fall. Some species are critically linked to plankton bloom, such as perch. Some research shows that the timing of perch larval hatch coinciding (or not) with the plankton bloom is crucial for recruitment. Even a week or two in either direction can miss the bulk of the plankton bloom, which is one reason why perch recruitment can be boom or bust. The 2015 spawn (after a cold winter) likely hit that bloom just right, and all those larval perch got on food right away. Research has shown egg quality tends to be higher for perch during colder winters too
Here's an exerpt from a paper talking about climate effects on fish recruitment
climate-induced warming can alter the timing of
spawning. For example, Lyons et al. (2015) documented earlier spawning in Lake Michigan yellow
perch in response to an earlier spring onset, with spawning advancing by 1.8 d to 6.8 d per decade since the 1980s.
Similarly, Farmer et al. (2015) and May( 2015) documented earlier spawning for Lake Erie
yellow perch and walleye, respectively, following warm winters with an early spring onset relative to
cold winters with a delayed spring onset. Lyons et al.(2015) also provided evidence to indicate that Lake
Michigan lake trout spawned later during the fall during the past several decades, which matches
theoretical expectations associated with a longer fall growing season (i.e., delayed winter onset)
Most notably, a climate-driven alteration of the spawning time can lead to mismatches between newly hatched
larvae and their planktonic prey (Durant et al.2007; Thackeray et al. 2010, 2013). This mechanism was
posed as a possible reason for consistent failed yellow perch year-classes in Lake Erie following short, warm
winters, in addition to the negative effects of a short winter duration on egg size and hatching success
(Farmer et al.2015). Specifically, Farmer et al. (2015)
showed that, although yellow perch spawn earlier after
a warm winter (and early spring onset), the shift was
somewhat constrained (advanced by about 1 week)
relative to the shift in the thermal regime (advanced by
about 3 weeks). In turn, following a short, warm
winter, yellow perch larvae may hatch too late after the
peak in zooplankton production to allow for sufficient
feeding to promote recruitment to the juvenile stage
In plain english, following warm winters, perch spawned about 1 week earlier than normal, despite water temperatures being advanced by about 3 weeks. That 2 week mismatch could be crucial
However.... note that warming surface waters could lead to earlier thermocline formation (stratification) which is useful not only for fishing in terms of finding fish, but it acts as a barrier to wall off mussels from filtering the upper water column, where phytoplankton are creating the base of the pelagic food chain. It's very possible that mussel impact could be mitigated a bit by warming water. Although the caveat with their metabolism increasing applies here too.
Spring is a period when the larvae of many
ecologically and economically important obligate
zooplanktivore fishes are in high abundance (Ludsin et al.
2014). Because thermal stratification is expected
to start earlier and last longer in large lake ecosystems,
including the Laurentian Great Lakes (Kling et al.
2003), the ability of quagga mussel grazing to suppress
phytoplankton production during spring would be
expected to decline. In turn, zooplankton availability
to larval fish during the spring could increase, through
bottom-up effects (Bunnell et al.2014).
7) I think one of the hardest thing about increasing temps is that the eye test is really not that useful, since we're talking about small to modest increases over a long time period, and there is a lot of variability. This is one of those cases like you referenced when you have to trust the professionals that have extensive data sets and know how to interpret them. Here's a good overview of the Great Lakes region
glisa.umich.edu/climate/temperature. The great lakes are by and large increasing in temperature faster than the air temp increases, because of the albedo effect I mentioned in my first post. With warming air temps and warming lake temps, there is less ice cover. Ice and snow cover reflect sun energy. With less ice and snow to reflect sun energy, the lakes absorb more of that energy, and warm up quicker in the spring and as a result cool down slower in the fall. Leading to less ice, and a positive feedback loop
Incidentally, there's lots of stuff from MSU that basically says all the same general things as this Purdue study. I'm not sure where that perception there is conflicting information is coming from...? Yu-chun Kao is at Michigan State, and that is referenced in the Purdue study. The 5 to 6 degree increase in summer surface temps in Lake Michigan is coming from Michigan State paper.
Here's another paper out of MSU talking about great lakes water temps increasing, for example
www.researchgate.net/publication/2441852...etween_1968_and_2002 
