Questions and Answers: Morning Session

Question 1: (John Higgins, The Nature Conservancy) When building climate change models based on mean values, you often see very similar degrees of fluctuation, as in the models just shown. But people working with climate change models and hydrologic changes are often very interested in the variance, since the predicted change in variance could be greatly increased with climate change. For example, though the lake level highs and lows have not changed dramatically in Lake Huron and Lake Michigan over the last 70 years, the variance of changes is larger than the difference of highs and lows. So, IÕm wondering if youÕve developed any variance in your models to allow for more extremes to result from the models.

Response: (Brent Lofgren, Great Lakes Environmental Research Laboratory, NOAA) Hopefully in the next year, daily data will be used more as inputs into hydrologic models to incorporate a little bit more of the change in variability that is projectedby the GCMs. But how reliable the projected change in variability will be is a question worth asking. Another question to ask is: “What kind of analyses will we want to do with this variance data?” Specifically, what time scales will we look at? Are we interested in looking at storm activity on a weekly scale? Are we interested in looking at lake level rise over a five-year period? All of these kinds of analyses will require a lot of data handling, so these questions will need to be considered.

Question 2: (George Stone, Milwaukee Area Technical College) What is the “shelf life” of the Canadian and Hadley models? How often are they revised? Also, it seems as though we´ve had an unusually cool, wet spring in the Great Lakes region. Is there any evidence thus far that that has had any effect on lake levels?

Response: (Brent Lofgren, Great Lakes Environmental Research Laboratory, NOAA) Actually, the Hadley Center has recently come out with a new version of its model, the HADCM3, for which the results have begun to be published. Interestingly, the results of this new model agree more closely with the Canadian Climate Center model that we have been using. One of the major changes of this new Hadley model is in its handling of atmospheric aerosols that reflect sunlight, and [the model now] ends up projecting warmer temperatures into the future [than before]. Whatever the newest model is, that is the one that is essentially considered to be the best. As for the recent low temperatures and high precipitation rates, such trends need to build up over a couple of years to create a significant change.

Question 3: (Thomas Johnson, Large Lakes Observatory, University of Minnesota Duluth) The modeling results look promising for fishing on Lake Superior, since availability of prey increases with rising temperatures. I am interested in knowing to what extent fish production in the Great Lakes is linked to phosphorus input to the lakes. Has anyone done a very simplistic comparison of overall fish productivity in the Great Lakes and the overall phosphorus levels?

Response: (John Magnuson, University of Wisconsin-Madison) If you add phosphorus to a point and have increased algal and subplankton productivity, you get the classic bottom-up effect. If you compare lakes, about half of the variability is often associated with this kind of bottom-up effect, so you would expect phosphorus availability to play a role. Years ago, Dick Ryder developed an index of fish yields from lakes that consisted of a simple ratio of total dissolved solids (which would include nutrients), divided by mean depth. That simple ratio explained a lot behind the yields of fish in lakes around the world. So, it is well established that those bottom-up effects are real. If it goes up and up, you begin to get a change in status—for example, if the deep waters get anoxic (oxygen depleted), then the whole framework will change. But I haven´t seen anything presented today that suggests that the waters are going to go anoxic in a hurry.

Question 4: (Thomas Johnson, Large Lakes Observatory, University of Minnesota Duluth) One of the reasons that I am asking about phosphorous in Lake Superior is that its bedrock is different from that of the other Great Lakes. Because Superior doesn´t have limestone and therefore doesn´t have the high total dissolved solids, I´m wondering what kind of impacts warming might have on it.

Response: (John Magnuson, University of Wisconsin-Madison) These models that I presented are very simple. If you began to include the whole food web and productivity and some of the feedbacks, you would get a lot greater variety of scenarios. Both because of its shape and runoff of nutrients into the area, Superior will remain a low-productivity lake, even with a lot of activities going on. I would imagine that of all the Great Lakes, Superior is the one that is most susceptible to a food web shortage.

Response: (John Lehman, University of Michigan) Just because a lake is low in total dissolved solids, that doesn´t mean that it can´t become ibritrophic, and that was the reason for choosing these lakes for nutrient experiment work. Inputs of nutrients from the watershed will be largely controlled by anthropogenic processes, and we don´t know what the future holds for population migrations and how inputs will change. Another dimension to look at is the lake geometry index—a geometrical factor that has a fair bit of predictability. Lake geometry affects whether or not lakes will form strong thermal stratification and become depleted of oxygen in the deep layers. And, of the Great Lakes, Superior and Ontario are the most susceptible to forming strong thermal stratification and deoxygenation according to that ratio. So, it will be interesting to see if the predictions of these mixing models hold up and if the duration of thermal stratification in Lake Superior increases faster than that of the other lakes.

Question 5: (Lon A. Couillard, City of Milwaukee, Milwaukee) Waterworks What is the potential effect of climate change on algal blooms? How might it affect the water quality for domestic water producers? Response: Art Brooks, University of Wisconsin-Milwaukee There has already been an increased abundance of some algal species growing on rocks along the shores of Lake Michigan, which are likely explained (at least in part) by warmer water temperatures. Generally, in warmer water, there tend to be greater numbers of cyanobacteriaÑbluegreen algae that do somewhat better under lower nitrogen levels, since they can fix their own [nitrogen] from the atmosphere. So, we might see some changes in this respect.

Response: (John Lehman, University of Michigan) Increased duration of thermal stratification will lead to a relative loss in the number and success of the diatom species, which are opportunistic, fast-growing clean water algae. However, diatoms cannot tolerate high rates of loss, so an increased duration of thermal stratification may lead to their replacement by either colonial greens—which may not present much of a problem other than filter cloggingÑor by colonial or filament-forming bluegreens—which can present more of a problem, in terms of taste, odor, and general nuisance.

Response: (Harvey Bootsma, University of Wisconsin-Milwaukee) One must consider the multiple effects that climate change will have. Warming will affect algae production and composition. But as changes in thermal structure and stratification occur, some modeling suggests that production will actually decrease, because the longer stratified period does not allow nutrients to get to the surface water. What we might expect to see is different effects in near versus offshore areas. Offshore areas are more dependent upon annual mixing to bring up nutrients, whereas near-shore areas may be more responsive to inputs from catchments (where surface runoff is gathered). Therefore, even with constant nutrient inputs, near-shore areas will be more responsive as temperature increases.

Response: (Art Brooks, University of Wisconsin-Milwaukee We have talked about some of the hydrologic effects and the fact that water levels may drop, which means that most intakes would be drawing in more surface water than deeper water, which in turn may mean that more productive water will come in, due to the physical factors.

Response: (John Magnuson, University of Wisconsin-Madison) A paper was written on year-to-year variation of water clarity in Lake Mendota and what the statistical explanatory variables did over the last 30 years or so. It was found that water clarity was equally influenced by three things—all three of which will be influenced by climate change: (1) Runoff—which will probably increase due to increased precipitation; (2) Stability of the water column—where the warmer the water—the warmer the summer—the less erosion of the deeper nutrient waters there will be during the summer, ultimately resulting in less upwelling or internal reloading of phosphorus; and (3) Population size of daphnia—a herbivore that feeds on phytoplankton. Daphnia varied based on the abundance of fish that [feeds on] them. In the eastern part of Great Lakes, we have a number of very effective warmwater zooplanktivores—the probability that they would become dominant in our systems would increase under a warmer climate.

Question 6: (Patty Glick, National Wildlife Federation) Has anyone looked into how reduced lake levels may affect species that rely on lake shores for breeding and other purposes? Response: Art Brooks, University of Wisconsin-Milwaukee Based on aerial photographs of the Mink River, we have seen great variations on the extent of wetland areas along the coast. The photos revealed that the wetlands increased and decreased by several orders of magnitude over a 10-year period, ranging from a trickling stream to a wide flooded wetland area. Since climate change will only exaggerate the natural variations that already occur, the implications of climate change on wetland production and nursery areas are very significant. This will affect productivity.

Response: (John Magnuson, University of Wisconsin-Madison) John Brazner at the EPA lab in Duluth would be a good resource person to speak to regarding the effects on lake shore species. Other effects to consider may be the within-year variations. For example, if water levels were to drop rapidly, fish species that spawn in the sand and the gravel might be stranded—but that would have to be fairly fast-moving water level drops. During the winter, fishes like the whitefish spawn on rocks just below the high water mark, and if there were a large loss of water in the winter, one might expect exposure of the ice settling on them. But I think those [effects] are unlikely, though it will depend on how big the variation is. Response: John Lehman, University of Michigan Another potential impact would be from a change in ice scouring that can occur during the winter—during the modification of shallow water habitat.

Question 7: (Patty Glick, National Wildlife Federation) Do researchers know how natural variations of lake shore levels affect different populations of species over decades? For example, do we know how water level fluctuations affect different populations of species, such as impacts on hatching rates? Response: Art Brooks, University of Wisconsin-Milwaukee I suspect that some work has been done on that, though I am not familiar with any such research. Certainly, inter-annual variations such as the extent of ice cover, the duration of spring mixing, and other things of that nature would affect phytoplankton production. Response: John Lehman, University of Michigan We havenÕt analyzed numbers specifically in that way. There is anecdotal evidence in terms of some invertebrate species development; for example, we know that fast-growing species that do well in warm water are successful members of the fauna during unusually warm years—but no systematic review has been done.

Response: (John Magnuson, University of Wisconsin-Madison) In the fish literature, there are correlates of year-class reproductive success in some species that are related to climatic factors that may be linked to water levels, but they may not actually be directly caused by the water levels. For example, walleye usually do better in situations where there is more runoff in the spring, and perch have higher reproduction in springs that are warm and dry instead of springs that are cold. Sorting out the exact causes for high or low productivity would be difficult.

Question 8: (Dave Michaud, Wisconsin Electric Power Co.) Given the demonstrated effects of zebra mussels in the near-shore area on phytoplankton and maybe even on benthos, would it be difficult to discern the effects of climate change in the next 30 years from the effects of zebra mussels and other exotic zooplankton that are already causing damages? How hard is it going to be to discern global climate impacts from exotic impacts?

Response: (John Magnuson, University of Wisconsin-Madison) Discerning the causes and impacts of climate change from all other variables is difficult, but scientists enjoy trying!

Question 9: (Dave Michaud, Wisconsin Electric Power Co.) Based on recent observation from being a large water user along the western coast, I can tell you that we have had to spend almost $10 million dealing with the zebra mussel, both in terms of direct and indirect impacts. Given the tremendous impacts that have occurred in the near-shore area from one species alone, I have serious doubts as to whether we can even begin discerning subtle changes in trophic-level dynamics, when there are monster invaders causing so many changes.

Response: (John Lehman, University of Michigan) But climate change and invasive species are not necessarily independent issues. Changes in the physical environment, such as temperature and mixing, in many ways facilitate the introduction of exotics and will increasingly continue to do so. Lots of introductions are occurring all of the time, but we only notice the catastrophic ones that affect us. But, as mixing patterns change and the vertical extent of warm water changes, deep water intakes that are currently unaffected by the zebra mussels, thanks to cold temperatures, may be affected in the future when the water warms. So there may be an interaction between climate change and exotic species in the future.

Response: (Art Brooks, University of Wisconsin-Milwaukee) Another unknown that should be considered in the Great Lakes is the fact that these are managed systems, yet managers of the lakes have not paid any attention to climate change projections and are continuing to practice the same behaviors. If they decide to put more salmon or trout in the lake, that could change the whole mix as well. So we are not just looking at a random input of exotics, but maybe a purposeful input of exotics that scientists have minimal control over.

Response: (John Magnuson, University of Wisconsin-Madison) Though zebra mussels are no doubt a pressing issue for the hydroelectric industry, and climate change may not influence the industry in the same way, climate change may influence how you place inputs, or the efficiency of your cooler system. The navy has already started thinking about how they would deal with military issues in an ice-free Arctic! This demonstrates the long-term investment time for which some people are, and must, think about to protect certain interests. So, the only thing that I can encourage people to do is not to get too caught up in dealing only with the most pressing issues of the day, but also to think about some longer term problems that will affect them in the future.

Response: (Harvey Bootsma, University of Wisconsin-Milwaukee) Certainly, introduction of exotics does make it very difficult to predict what will happen in the future. But, as mentioned earlier, though phosphorus inputs can explain about 50 percent of the variability in primary production and other top-down mechanisms also influence this variability, that does not mean that it is not useful to look at the relationship between phosphorus and chlorophyll. In the same respect, despite variability and the complexity of factors that affect lakes, it is still worth considering the potential impacts of climate change on lakes. There are fundamental physical factors that we need to know about lakes as a result of climate change. Even though there will be other changes superimposed on these climate change-related impacts, our ability to predict the results of exotics is improved by fundamental background data that will allow us to better know how systems will change over time.

Question 10: (Alberto Vargas, Wisconsin Coastal Management Program) What are the next steps that should be taken to further the climate change debate? What is the role of science? Do we need to refine predictions? Provide economic assessments for different scenarios? Based on what newspapers are saying, the discussion is not so much centered on whether or not climate change is happening, but on the economic implications.

Response: (Peter Sousounis, Michigan State University) What we have learned from the first assessment is that we need to expand on three major areas: (1) we need a better understanding of the inter-annual/decadal variability of systems from year-to-year, not by mean; (2) we need to conduct more interdisciplinary studies; and (3) we need economic answers. For the latter need, since stakeholders have the best idea of how weather may affect their industry, scientists need to foster better relationships with stakeholders and provide them with the necessary information for them to determine the economic answers.

Response: John Magnuson, (University of Wisconsin-Madison) We need to know what the impacts may be and what potential adaptive strategies can be adopted. Most people do not propose adaptive strategies but simply believe that weÕll just have to cope with whatever changes result. Also, the climate system needs more work. For example, the U.S. needs to know more about its carbon budgetÑwhere are the sinks? Are there adaptive mitigation measures to be taken in agricultural, forestry and/or lake management to increase carbon storage? We also need to keep providing policymakers with information to allow them to develop an action strategy on climate change at the international level. So, there is clearly a large role for communication and educationÑlots of priorities!

Response: (John Lehman, University of Michigan) Studies have revealed that there is much uncertainty and a great need to fill in the gaps in our scientific knowledge. For example, maybe we need to know more about seasonality of maximum rates of primary production. Therefore, in addition to exploring the socio-economic side of the problem, we also need to know how good a job we are doing at putting the right numbers into our equations. An example of uncertainty worth further interdisciplinary research is the variation in cloud cover during the day and night. Cloud cover variability can have a huge impact on climate and lakes. These impacts, which could have huge effects on projections, cannot be deciphered from the GCMs but will need to come out of mesoscale models. But right now we donÕt much data on cloud cover, so these impacts are still largely unknown.

Question 11: (Jo Sandin, The Milwaukee Journal Sentinel) How will we be able to find out variability in cloud cover between day and night, now that the National Oceanic and Atmospheric Administration (NOAA) has replaced humans with machines that are not capable of monitoring cloud cover? Nobody is looking out the window anymore, because we are not paying anyone to do it. Do we know if it will be cloudier in Milwaukee?

Response: (Peter Sousounis, Michigan State University) It is hard to pay observers 24 hours a day. Remote sensing does actually have some advantages. It allows more spatial cover over remote areas of the lakes and the algorithms used to interpret satellite data are getting better and providing more accurate numbers for cloud cover. On the whole, satellite-derived cloud cover is probably doing a better job than human observers could. The algorithms are compared to mesoscale output, which will help refine both. Using this newly refined information, we hope to obtain better estimates of how cloud cover will change the picture.

Response: (Brent Lofgren, Great Lakes Environmental Research Laboratory, NOAA) The problem with remote sensing is that it eliminates the temporally homogenous record at any one point of cloud cover that one would get by using a consistent method of measurement. In most cases, one would want an overlap of several years, but some things, such as cloud base height, are not necessarily measured by satellites. A similar problem has arisen with the elimination of river flow measurement sites maintained by the U.S. Geological Survey, which has occurred at some sites in the Great Lakes basin over the last few years.

Question 12: (Patty Glick, National Wildlife Federation) Despite the many uncertainties that exist in the current science on global warming, there is very little uncertainty that human activities are causing the Earth to warm. Yet, by constantly talking about uncertainty, policymakers hone in on the different layers of scientific uncertainty and then do not act. As scientists, do you feel comfortable conveying so much uncertainty, knowing that the declaration of uncertainty causes policymakers to delay action?

Response: (John Magnuson, University of Wisconsin-Madison) As scientists, we must say what we feel confident about and what we feel uncertain about, or we are lying and cheating. Policymakers need to decide if, in the face of uncertainty, we should act conservatively or take the risk-prone approach. What people have discovered in the past is that we would have been well off to have taken the risk averse strategyÑknown as the precautionary principle. So, most scientists would tell policymakers that if youÕre looking at an uncertain future, you should take the cautious approach. Science only plays a certain role in deciding policy. As scientists, our role is to reveal the uncertainty to force political debate on important environmental issues. Scientists can only reduce uncertainty; they cannot eliminate it. Comment: George Stone, Milwaukee Area Technical College An important part of risk assessment is to ask the question, ÒWhat are the consequences?Ó There is uncertainty about contracting or not contracting a disease, but that does not cause people to forgo inoculation. Likewise, we do not know when or where earthquakes are going to occur, but that does not prevent us from passing building codes and construction requirements to prevent casualties and costs if an earthquake does occur. I think this kind of approach, where you take not only probability into account, but also the severity of the consequences, is important for policymakers to consider.