Tahoe Forecast: Shrinking Snow, Longer Walk to the Water

Lake Tahoe's water level could drop within the century. (Photo: Lauren Sommer)

The average snowpack in the Tahoe Basin could decline 40 to 60% by 2100 and some years could see all rain and no snow. That’s according to climate change forecasts released this week by the UC Davis Tahoe Environmental Research Center.

The decrease in snowpack would be driven by two processes, according to study author Geoffrey Schladow. With warmer temperatures, more precipitation will fall as rain during the winter, instead of snow. And as any skier knows, when rain falls on snow, it melts the snowpack in what scientists call “rain-on-snow” events.

These findings are a concern since the Sierra Nevada snowpack is often called California’s “frozen reservoir.”  That reservoir is critical to the state’s water supply — and it’s free. “What the snowpack affords us is a way to very economically store water,” said Schladow. “If the water is falling as rain, rather than snow, then we have to build more dams and reservoirs to catch it, which is expensive.”

The study also forecasts several climate change impacts on Lake Tahoe itself. Prolonged droughts in California could cause the lake level to fall below out-take valves, which feed the Truckee River. The Truckee supplies water to Pyramid Lake and the city of Reno, Nevada. Output levels have fallen in the past, but under the worst case climate change scenario, those periods could stretch 10 to 20 years.

That would also change the face of the iconic lake. “Suddenly lakefront homes would be hundreds and hundreds of feet from the water. It’s going to be a very different looking lake,” said Schladow.

Lake Tahoe’s unique ecology could also change. Mixing of water from different depths is a critical process for any lake, since it takes oxygen from the surface and makes it available for fish and other species living throughout the water column. Because Lake Tahoe is so deep, today it only mixes fully every three to four years. By the second half of the century, that mixing period will become longer. “At some point, it may not mix for decades at a time,” said Schladow.

Schladow says the study focused on Lake Tahoe as an important case study for changes happening throughout the Sierra Nevada. “These same processes are happening everywhere across the West. Tahoe is the canary in the coal mine.”

Forecasting climate change impacts like these at the regional level has become a Holy Grail for climate scientists. Historically, computer climate models could only scale down to sections of land hundreds of miles across, which made it difficult to predict changes in a landscape as varied as California.

Schladow says newer climate models allow them to see changes at a much more granular level. “What we were able to do is to use grids that were more like one or two miles. That way we could distinguish between effects at the mountain peaks and effects down at the lake level.”

Schladow is hopeful that this study can give land and water managers an early indication of what the future may hold.

  • http://ncwatch.typepad.com/ Russell Steele

    Dear Congressman Tom McClintock

    The study listed below was published yesterday and the results are all based on computer models. As every scientist and computer programer knows you can make a computer model say just about any thing that you want. It appears the authors started with the asumption that human activity is causing global warming and then proceed to model the results on Lake Tahoe. There is no scientific proof that anthropogenic greenhouse gas emissions are causing global warning. The current claims for AGW are yet again based on computer models that can not be verified. So far the anthropogenic greenhouse gas emissions models have fail to show the last 15 years of global cooling, or the ocean cooling trend that started in 2003.

    My question: With Sierra Nevada Counties unemployment soaring, is spending money on computer models and 200 page reports that are nothing but intellectural crap the right way to spend tax payer money? I think that money from Sierra land sales should be spent on job creation, not the creation of useless reports based on bad science. As a member of the Natural Resources Committee, I hope you can put a stop to this waste of tax payers money.

    Respectfully,

    Russell Steele
    Nevada City, CA
    530-273-8085

    THE EFFECTS OF CLIMATE CHANGE ON LAKE TAHOE IN THE 21st CENTURY: METEOROLOGY, HYDROLOGY, LOADING AND LAKE RESPONSE

    Abstract
    The 21st Century global climate is expected to experience long-term changes in response to anthropogenic greenhouse gas emissions. Discussions on the potential impacts of climate change on water resources in the Lake Tahoe basin have only recently begun and our scientific understanding to date has focused on identifying existing impacts and trends in the historic data. Water resource managers need to know the potential effects of changing meteorologic conditions on a variety of topics such as expected future air temperature, amount and type of precipitation, stream discharge, sediment and nutrient loading characteristics, BMP performance, lake mixing and water quality response. In this study we examined all these topics using existing water resource models already developed for the Lake Tahoe TMDL. A sophisticated statistical downscaling methodology was applied to the model outputs of the of the Geophysical Fluid Dynamics Laboratory Model (GFDL) and the Parallel Climate Model (PCM) given the A2 and B1 emissions scenarios, to produce simulated data records at a 12 km grid scale in the Tahoe basin for the 21st Century (2000-2099).

    7.7 Acknowledgment
    This research was supported using funds provided by the Bureau of Land Management through the sale of public lands as authorized by the Southern Nevada Public Land Management Act (SNPLMA), and was funded in part through grant 08-DG-11272170-101 from the USDA Forest Service Pacific Southwest Research Station. The views in this report are those of the authors and do not necessary reflect those of the USDA Forest Service Pacific Southwest Research Station or Bureau of Land Management.

  • JWH

    Russell, These climate models are quite advanced and are now able to show us potential impacts on a regional basis which is very exciting. Is your beef with the models or the thought that global warming is occurring? Humor us and take a couple of courses in chemistry and physics; you will quickly catch up with the rest of us. Strikes me that once you are over the hump of skepticism, you will want to know the impacts. Many of us both in and out of the scientific community want to know, indeed, need to know. These include business and agricultural interests to name a few. Thanks.

  • http://ncwatch.typepad.com/ Russell Steele

    JHW, who ever you are, wrote:
    “These climate models are quite advanced and are now able to show us potential impacts on a regional basis which is very exciting.”

    No matter how advanced your models are, they are all driven by the input parameters and the equations used to calculate the out put. All of those are devised by humans, any with an agenda. Therefore, your advanced models can only produce more detailed crap than a simple model. Who is validating your models in put? What third party has quality checked and validated the data used in the models? What independent organization with no skin in the game has validated the algorithm used for the calculations? We know from the Climategate emails and code that “fudge” factors were used in the climate models, and that some of the data was made up? Who is willing to certify that your models do not contain fudge factors and made up data? Really?

    I ran an organization that was responsible for third party validation and verification of software used in advanced weapons systems. We built tools necessary to find the errors in software and systems integration that could turn a pilot a little greasy spot on the ground. We used models to represent the real world as inputs to our tools and I know models are limited by the input parameters. How those parameters are chosen and validated is reflected in the modeling out put. What third party, with no skin in the game, has validated your advanced models? Oh?

  • Dixon Cruickshank

    We have been doing models on hurricanes for far longer than climate and with much better information available – much better. Results are far from even close other than figuring out landfall a day ahead or less. I was personally in the direct path of Hurricane Charley – direct meaning the cone centerline went over my house within 24 hrs.of landfall. Result was it made landfall not in Tampa but Punta Gorda 125 miles away and I didn’t even get much rain – so much for trying figure the weather 30 yrs out assuming 10 different paramiters – its a guess, and probably not even a good one.

  • Greg Goodknight

    “Humor us and take a couple of courses in chemistry and physics; you will quickly catch up with the rest of us.” is the sort of snark that makes it difficult to have a conversation.

    “JWH”, I took lots of physics on my way to a degree in same, and took the same lower division chemistry courses the chem majors did. You?

    I went from lukewarmer to skeptic to scoffer in early 2007 when I became aware of research, which I sought out and read for myself, that has been actively ignored by the fairly insular climate modeling and activist communities.

    What does the climate community think about the robustness of their science? Let’s see what James Lovelock, environmentalist and futurist extrordinaire, father of the “Gaia” theory, had to say last March: “The great climate science centres around the world are more than well aware how weak their science is. If you talk to them privately they’re scared stiff of the fact that they don’t really know what the clouds and the aerosols are doing. They could be absolutely running the show. We haven’t got the physics worked out yet. One of the chiefs once said to me that he agreed that they should include the biology in their models, but he said they hadn’t got the physics right yet and it would be five years before they do. So why on earth are the politicians spending a fortune of our money when we can least afford it on doing things to prevent events 50 years from now? They’ve employed scientists to tell them what they want to hear.”

    Let’s stop the ugly rhetoric and get the physics right. Clouds, aerosols and the sensitivity of the climate to CO2 and other ‘greenhouse gases’ need to be correctly handled in the general circulation models before they can be even *begin* to be used rationally in the setting of public policy. If you want to learn some of this physics, I’d suggest as a start going to this list of papers and read anything that includes (not a complete list by any means) J Veizer, N Shaviv, H Svensmark or R Lindzen as an author:
    http://www.populartechnology.net/2009/10/peer-reviewed-papers-supporting.html

  • James Mayeau

    I thought accurately modeling the effect of clouds was the holy grail of climate modeling, or if aerosols are a positive or negative forcing was the holy grail.

    I guess there’s lots of holy grails of climate modeling.

    Interesting that global warming always hurts the things we love. Cute little mountain bunnies, fluffy white polar bears, brightly colored clown fish, tropical paradise islands, and now distant snow covered peaks.
    Is there anything wonderful and good that co2 doesn’t ruin?

    • james

      It’s not that distant for me. It’s a four hour drive to go snowboarding.

  • Dixon Cruickshank

    No worries James our tropical islands in Fla are doing just fine and the palm tree’s and hibiscus seem to like it too. Although many didn’t survive the brutal winter last year but I degress.
    Haven’t run across you lately, nice to see you

  • Greg Goodknight

    Where did “JWH” run off to?

  • James Mayeau

    Maybe checking the property – making sure nothing got left out in the weather? We got a big storm brewing.

    Dixon you see me everyday. It’s me, Papertiger. You know. Halloween’s over so I dropped the mask.

    hey but still don’t tell Pelline. Don’t want to help him out.

  • Andy

    Metereorologists began to develop and employ models as the only scientific way to forecast weather. They began doing this in the 1940’s, way before computers were even around. The folks who’ve developed the models that predict the globe’s climate such as the Goddard Institute for Space Studies (GISS) and the Jet Propulsion Laboratory (JPL) among others have carried on the tradition of being at the leading edge of computer modeling of complex physical systems.

    Of course this would be meaningless if the climate had not responded as predicted by their relatively crude models in the 1970’s. They’re new models of course blow the old ones away and are proving better and better at pinning down what our future climate will look like.

    Bottomline – they’ve been making correct predictions for 40 years now regarding global warming.

    In terms of Lake Tahoe. The eastern side of the Sierra Nevada is strewn with dead lakes that 10,000 years ago were hundreds of feet deep. Lake Manley (now Death Valley), and Lake Russell at the head of the Owens River (now a much smaller Mono Lake) for example. The Great Basin was filled with large lakes and had a very equitable climate as a result. A little bit of warming, the lakes dried up, and it all came to an abrupt end.

    A few degrees of warming will predictably move the deserts up in elevation whereas lakes like Tahoe will no longer be able to make up their evaporation deficits. It’s all pretty simple.

    A very good reference regarding the Great Basin including the past history of the Tahoe area is: The Desert’s Past: A Natural Prehistory of the Great Basin by Donald K. Grayson. Smithsonian Institution Press. 1993.

    As far as hurricanes go; I’ve lived on the Texas coast for 30 years. The ability of the NHC to forecast tracks has gotten very, very good over the last 5 years. Predicting Charley’s storm track was a feather in their cap. Charley missed Tampa/St. Pete by only 40 miles (120 miles only if you follow the coastline around). These towns were on the dry side of this very powerful, but very compact storm. Predictions this accurate made almost a week ahead of time are truly amazing (look at the National Hurricane Center’s History page for details on all storms and track predictions).

  • Greg Goodknight

    “Andy”, you seem a bit starstruck. The theory of CO2 warming isn’t even 40 years old, and the first crude models predicting warming aren’t much older than 20 years. The models didn’t predict the warming of the last 40 years, they have been parameterized to *fit* the warming of the past 40 years.

    Yes, it’s warmed since the last glaciation. This too shall pass, eventually. The first humans to live in the Americas walked here about 12,000 years ago over a land bridge where the Bering Strait is now. What was ice is now ocean. It will be ice again sometime.

    Those parameterized models, expecting the past warming having been due to positive feedbacks involving water vapor, predict significant warming in the future. They also predict patterns of temperature in the atmosphere NOW, and those temperature patterns, including a hot region above the equator, are not there. By traditional standards of science, that means the models have been falsified. Invalid.

    The warming of the past 40 years is better explained through natural variations that have only recently been identified, including temperature oscillations of the oceans and the role of the sun in modulating cloud formation. CO2 is just not as important as you have been led to believe.