Most of us don't think about risk. We think about randomness. That's illustrated by a scene in the 1982 movie, "The World According to Garp", where Robin Williams is shopping for a new house with his wife. They're standing in front of one home when a plane crashes into it.

Despite the crash, the Robin Williams character agrees to buy the house saying, "It's been pre-disastered! We'll be safe here."

That may not be a typical reaction, but climatologist Kelly Redmond says it reveals a lot about how we think about risk. "It has to do with how we describe rare things. We spend societally an enormous amount of resources and time and attention guarding against the very worst possibilities."

You've probably heard of the "100-year flood." That's a flood so severe that it has a one in one hundred chance of happening every year. But how do we know that?

"About the only way we can get at how rare a rare thing is is by looking at a past record," says Redmond. So for floods, government agencies look into the historical record to see when floods happened in the past. They use that record to predict future flood risk.

But this relies on a very basic assumption. According to Redmond, the assumption is that the statistics of the future will look like the statistics of the past.

There's a fancy term for this – it's called stationarity. But there's a problem.

"What we don't know but what we suspect with changes in climate is that those statistics, especially about rare things, may change," says Redmond.

The US is already warming. Climate models show that western states could see more extreme weather as the climate continues to change. So, Redmond says, chances are good the future won't look like the recent past.

Jeanine Jones of the California Department Water of Resources agrees, saying "a lot of California's existing infrastructure was designed on assumptions that are no longer valid."

History of Water Forecasting in the West

Jones says using the past as a guide for the future is a huge part of water planning and building codes. The idea was first adopted in the 1940s and 50s, when dams and infrastructure were built at record speed in western states.

"Congress was looking at all these water development plans coming in from the Corps of Engineers and the Bureau of Reclamation and wanting a common standard to compare all the projects," says Jones.

So they forecasted flood risk and water supply by looking at historical data. "But they had very short data records. Maybe they only measured records of 20 years, 50 years. And that's not really very long," Jones says.

Today, everything from building codes to home insurance is based on this short window of data. And so is another critical forecast.

During the winter, surveyors measure the Sierra Nevada snow pack every month, so they can crunch the numbers and predict the year's water supply.

"It is very widely used by reservoir operators, by water agencies, by farmers who are looking at what are my chances for having a full water supply," says Jones.

But climate models show that more precipitation will fall as rain in California, instead of snow. And that means spring runoff could behave very differently. "At some point, conditions will change enough that we've reached a tipping point where those statistical approaches really aren't valid anymore," Jones says.

An accurate water forecast is crucial to California's economy. So Jones says water officials are looking at using computer models to forecast spring runoff.

But when it comes to updating flood risk and building codes to reflect climate change, Kelly Redmond says that could take decades. "We have to get a buy in from the engineering community, the city planners. Because there's so much expense to goes into building a bridge or a culvert or a building."

A New Breed of Insurance Company

There is one industry that's taking note of climate change – insurance.

"The increased variability in climate is going to start to dramatically affect the profits of corporations worldwide," says David Friedberg, CEO of San Francisco-based The Climate Corporation.

The Climate Corporation is something of a next generation insurance company. They start with computer models that simulate weather and climate patterns. "We then use those sorts of models to determine what sort of price we should charge for certain weather events occurring," says Friedberg.

The company works mostly with farmers, insuring them against extreme weather for between 40 and 400 dollars an acre. "There's a range of things that can occur and that range is certainly widening. And as a result we should start to charge more for those sorts of events when we're insuring them."

Friedberg says this kind of insurance makes sense to a lot of farmers they work with, who are already noticing changing weather patterns. Investor Vinod Kholsa and Google have also noticed and put millions into the company. They're betting new software will be the answer when today's methods no longer work.

It's been a harsh winter across the US. Snow has blanketed the Sierra Nevada, where the snowpack is well above normal. Lots of snow means good skiing, but it also means an increased danger of avalanches.

Avalanches aren't something most skiers and snowboarders have to think about. That's because ski areas take preventative action.

On the backside of Squaw Valley Ski Resort, two ski patrollers drop into a black diamond run known as Granite Chief. Below them are mounds of fresh, untouched powder – more than seven feet deep.

The patrollers are throwing explosive charges onto the slopes to trigger smaller, less dangerous avalanches. Booms ring out across the mountain.

Listen to the QUEST radio story The Science of Snow

"The Sierras are known for getting tons of snow really quick," says Will Paden, the avalanche forecaster at Squaw Valley Ski Resort. "We're constantly trying to start the avalanches so that we don't let the snow pack build up to be too deep."

Paden says on a day like today, they'll use more than a thousand pounds of explosives to make the ski area safe. But the job isn't over when the snow stops falling. The snowpack is constantly changing.

"One day could be perfect powder and then that afternoon the wind can pick up and put wind crust on top of that perfect powder and make it difficult skiing," says Paden.

Avalanche forecasting is even more technical. "We had a lot of riming in this snow and some graupel events."

To translate that, you have to go inside the snowpack.

On a slope outside of Truckee, Brandon Schwartz uses a shovel to cut a cross-section in the snow. As a forecaster with the non-profit Sierra Avalanche Center, Schwartz has dug thousands of avalanche pits like this one.

An avalanche near Echo Summit in Lake Tahoe.
Credit: Travis Feist"We can feel the different hardness of all the layers that have formed in the snow that's fallen over the last two to three days," says Schwartz.

Schwartz is looking for weak layers of snow, which is where avalanches begin. He pulls out a saw and slices through the snow to isolate a one foot wide column. Then he places his shovel on top. "And we'll just start to load on top of it first with ten taps just from my wrist, just from lifting my wrist and letting gravity pull my hand down."

Those taps simulate what a little weight would do to the snowpack, either from more snow falling or from a skier.

Schwartz points to where the snowpack has broken away along a straight line. "So we got a pretty significant crack all the way across the column here. Definitely a difference in strength there and that's what makes up the layers of snow pack and when we have these layers of different characteristics then we start to get some of the ingredients for a slab avalanche."

Schwartz and his team travel into the backcountry every day to assess the avalanche danger in the Tahoe region. Of the 36 people who died in avalanches across the United States last winter, almost all of them were in the backcountry. A large storm like this one means today the danger is high.

But what makes some snow weaker than other snow?

"Once we have snow on the ground, a whole bunch of really interesting things happen. You think of the snow as being rather static, but it's not at all," says Jeff Dozier, an environmental scientist at the University of California-Santa Barbara who studies how snow impacts California's water supply.

Dozier says to understand what's happening, you have go all the way down to the level of a snowflake.

Check out the different types of snow crystals, as seen under an electron microscope:

Once the snow falls, the snow crystals will start to stick together. As they sit there, the crystals grow rounder and bond together. "And if you shovel snow, you see this. If you shovel snow when it's new, you can stick the shovel in the snow and you can lift it. You shovel snow when it's old, it's hard to break that block of snow loose from its neighbor."

When a lot of snow falls quickly like it does in the Sierras, this bonding process may not happen fast enough to support the snowpack, which leads to avalanches. The warmer a snowpack is, the faster it bonds. But if it's colder, sometimes a different kind of crystal grows.

"Typically the temperature at the base of the snowpack – this is gonna be around zero degrees C. But on a very cold night, the temperature at the surface say might be -20 degrees C," says Dozier.

That difference in temperature can create another shape of crystal – a faceted crystal. "They're sort of angular. They don't bond together very well."

These crystals look like grains of sugar and they create weak layers deep in the snowpack. A better understanding of snow crystals could help avalanche forecasters. Dozier says it could also help water managers trying to anticipate the snowpack melt in the spring, an event that's critical to the state's water supply.

Avalanche forecaster Brandon Schwartz in the field:

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El Nino temperature anomalies in the eastern Pacific Ocean.

Jennifer Skene's post earlier this week here on the QUEST Community Science Blog about the potential effects of this winter's La Niña is a great lead-in for discussing this climatic phenomenon in a bit more detail. As Jennifer noted, the La Niña weather pattern is the flip side of El Niño, which is when unusually warm waters of the eastern Pacific Ocean affect weather patterns for large swaths of North and South America. For California, El Niños typically result in increased precipitation in the winter months and La Niñas are characterized by drier conditions.

El Niño is the nickname of the climate pattern called the El Niño-Southern Oscillation, or ENSO. Although we don't hear much about the Southern Oscillation part, it is the atmospheric component of this linked ocean-atmosphere phenomenon. Although the physics of ENSO is still not fully understood and the subject of current research, the regularity of the pattern is well documented. The image below is a time series plot of ENSO events for the past 60 years. The positive values filled in with red are the warm ENSO phase (El Niño) and the negative values in blue are the cool ENSO phase (La Niña). The regularity isn't perfectly on beat — it varies from 3-7 years between measurable events. But this is enough regularity to make ENSO one of the more predictable patterns climate scientists have studied.

While the timing of ENSO cycles might have some predictability, the magnitude of ENSO (the height/depth of the peaks) can vary significantly. Some are weak while others are quite strong. The 1997-1998 El Niño is considered to be one of the strongest of the past 100 years and is still in the memory of many Californians because of the intense precipitation and subsequent flooding it unleashed.

What's really interesting is that this 3-7 year pattern of alternating ENSO phases is just the shortest timescale in a climate phenomenon with multiple rhythms superimposed. Paleoclimate research has revealed that ENSO also beats at timescales of hundreds to thousands of years. The image below is very similar to the above diagram — it has time in years on the horizontal axis and occurrence of ENSO events on the vertical axis. (Important difference to note are that the present is on the left side on this plot instead of the right side and time is in 'years ago' and not a date.)

This plot goes back to 10,000 years ago and shows the variability in ENSO at a much longer timescale. Within those taller peaks in the plot are numerous individual El Niños that are grouped together in time. This doesn't mean that every single El Niño is very strong — just that during a few hundred years there more of those strong El Niños. In addition to the peaks every several hundred years there is also an even longer-term trend of increasing ENSO events over 5,000 to 6,000 years.

Like a complex musical composition with multiple interacting rhythms, the interacting timescales of this climate phenomenon might result in weather patterns that defy our ability to predict confidently. The authors of the study looking at ENSO patterns for the past 10,000 conclude that bigger-scale changes in global climate (due to changes in the Earth's orbit around the sun) are driving those longer-timescale changes. A big question right now is how modern global climate change will affect ENSO. A warming ocean suggests El Niños will get more intense, but perhaps there are some unanticipated effects from the multiple interacting factors that still needs to be studied. We are improving our understanding of the Earth's climate systems but, as always, much more work needs to be done.

Images: (1) El Nino anomalies in the eastern Pacific Ocean; image from McPhaeden et al. of NOAA (2) ENSO Index from 1950-2010; image from McPhaeden et al. of NOAA; (3) Figure from Moy et al. (2002); Nature 420

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For demonstration on how advection fog is created (and how you can do this at home), check out this video we filmed with The Exploratorium's Eric Muller.

QUEST on KQED Public Media.

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While foggy days aren't ideal for a summertime picnics, coastal fog does benefit the ecology of the Bay Area.

Normally I wouldn’t be hoping for a chilly, foggy day during the summertime here in San Francisco. For the purposes of filming our Science on the SPOT story, “Science of Fog,” however, we hoped that the Presidio would be socked in with a thick blanket of fog for our interview with UC Berkeley’s Todd Dawson.

Luckily, Mother Nature cooperated with us to give us plenty of atmospheric fog to work with for our shoot. We interviewed Dawson about the two types of fog that are prevalent in the Bay Area, and about his ongoing research on the decline of fog along the California coast.

Dawson also elaborated on some conflicting reports in the media on whether fog was declining or actually increasing. “There was a study done previous to ours over a shorter period of time. It's only about 35 years. And the records came only from the Los Angeles area and from San Francisco. They weren't a comprehensive sort of investigation of all of the temperature records that we've done throughout California.

Those investigators came to the conclusion based on a model that they had developed based on those just temperature records, [with] no fog data. They ran the model, and it gave them an output that says, 'Oh, fog is going to be increasing.'

Our investigation is much longer. It takes place over more than 110 years. It's hourly temperature records and precipitation records. It involves all of the fog data from the airports that we've been able to get throughout the entire state. And, of course, it's a longer period.

And just like the stock market, if you look at a small part of a change in the stock market, on any given day it might look like it's rising. But if you look over 100 years of the stock market, you're going to say that, ‘Ah, stocks have been declining steadily over that longer period of time.’

So what looks to be a bit of a conflict is really just because we're looking at different windows of time and different kinds of information. And I think that's why sometimes people kind of go, "Well, somebody told me that fog's supposed to be increasing.’ And our data is saying no, it's decreasing. It kind of depends on the window of time you're looking at.”

And to learn more about why foggy days – while not ideal for a summertime picnic – benefits the ecology of the Bay Area, check out the Science of Fog.

QUEST on KQED Public Media.

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"2008 was one of the hottest years on record."

Just last week, Max Moritz and his team at UC Berkeley's Center for Fire Research & Outreach published a study that shows widely varied fire response to climate changes around the world. Post-doctoral fellow Meg Krawchuk was the lead data cruncher in the effort, with contributions from researchers at Texas Tech University.

What they found were suggestions of rapid changes in fire regimes, and not all in the same direction. Some places (like most of California) will likely see a spike in the fire hazard, while other regions (like the Pacific Northwest) could see a retreat of wildfire frequency and intensity:

"In contrast to any expectation that global warming should necessarily result in more fire, we find that regional increases in fire probabilities may be counter-balanced by decreases at other locations, due to the interplay of temperature and precipitation variables. Despite this net balance, our models predict substantial invasion and retreat of fire across large portions of the globe."

Moritz has been stumping for new approaches to fire-climate analysis. He says rather than treat fire strictly as the product of other climate change variables, we should think of it also as a climate driver.

Map shows areas of potential fire advance (orange) and retreat (blue) by 2010-2039 (medium-high emissions scenario)

You can use the player below to hear an excerpt from my interview with Moritz, in which he explains the new perspective that he thinks his team's study brings to the fire-climate connection.

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A confession: When I first got the assignment to do a story about air conditioner efficiency, I didn't exactly leap from my seat in excitement. (Which is why extra kudos go to those who've made it as far as this web page!) But, really, I should have known better.

AC seems mundane because it's ubiquitous – but because it's ubiquitous, its impact is astonishing. If you took air conditioning out of the picture, there might not be such thing as the California energy crisis. We could put dozens of power plants offline. In terms of global warming, it would be like taking hundreds of thousands of cars off the road, permanently.

Why air conditioning and not, say clothes dryers or refrigerators? Well, partly because AC sucks lots of power (especially central AC systems though, bought new, even those may be more efficient than your old window unit), partly because of the way we use them: all at once. When heat waves hit, Californians turn on their ACs practically in unison, hitting up a beleaguered electricity grid that fires up every creaky last turbine to handle the load.

So, it comes as no surprise that a number of Californians are putting serious energy into making air conditioning work better. At the top of that list is California Energy Commission Commissioner Art Rosenfeld, the efficiency guru who, perhaps more than any other person, can be credited for California's remarkable efficiency gains over the last 30 years. We also hear from AC inventor and entrepreneur John Proctor. And thanks also go to Jeff Scalier, of Antioch-based Blue Star Heating and Air Conditioning, who introduced me to his very satisfied customer, Al Mason, and whose mother I hope enjoys the CD we send her.

If you want to retrofit your central AC system to tailor it to California climate (and make it 20 percent more efficient) a number of Bay Area installers are ready to do it. Here are some of them, courtesy of Proctor Engineering:

– Vtech HVAC Services, Antioch, 925-752-6075

– Bland A/C & Heating, Inc., Bakersfield, 661-836-3880

– Herrera Heating & Air Conditioning, Bakersfield, 510-750-6972

– Action Air Conditioning, Clovis, Fresno, 559-292-8640

– California Indoor Comfort, Fresno Area, 559-276-7457

– Certified Heating and Air Conditioning, Fresno County, 559-273-8048

– ReNu, Marin County, 415-462-0245

– Queirolo's Heating & Air Conditioning, Inc., San Joaquin County, 209-464-9658

– Leo's Heating & Air Conditioning, San Joaquin Valley, 209-271-7873

– Air Solutions Heating & Air, Stanislaus County, 209-380-3032

– Air Flo Pro, Stockton, 209-915-4730

– University Refrigeration, Stockton, 209-609-8400

– CPR Sheet Metal, Inc., Vacaville, 707-628-7495

– Right Now Air, Vacaville, 707-447-3063

Listen to the Air Conditioning Reinvented radio report online.

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Riding to work on BART, about a week before I was to begin shooting this story, I ran into a former colleague of mine whom I had not seen since 2001. He and I had worked together for something like 9 years at KUSF, a non-commercial community radio station in San Francisco. The station -and this particular guy- have always had a reputation for being fairly progressive. OK, that might be an understatement: he's a militant vegan, Critical-Mass-bicycle-riding, anti-automobile, bleeding heart liberal who played a lot of 60's Psychedelia and Prog Rock like the Fugs, the 13th Floor Elevators and Frank Zappa on his radio shows.

After explaining to him that I was working on a story about the impact that global warming is having on the Earth’s supply of fresh water, I was shocked to find myself arguing with him about the very existence of climate change. He claimed that it was all a bunch of sensationalism and that the Earth's climate has always had dramatic changes and that what we are experiencing now is anecdotal and has nothing to do with humans. He said that even if it is happening, longer growing seasons in northerly regions would be beneficial to world food supply and that an increase in carbon dioxide in the atmosphere would cause plants to grow even better. Sure, I’ve heard these types of arguments before but usually not in San Francisco. It was definitely a timely reminder to me about why the media should cover the kind of scientific work that’s being done on this issue.

Given my conversation with BART guy, one of the reasons the Keck Hydrowatch Project is so interesting to me is that Inez Fung, Todd Dawson and the rest of the team aren’t actually setting out to prove the existence of climate change. The researchers are embarking from the position that without question, global climate change is happening and what we are experiencing today is just the tip of the rapidly melting iceberg. And you know what? I believe them. So, they are dedicating the next four years of their lives to understanding how these changes will affect the availability of fresh water for use by humans, plants and land animals. So far, their predictions are "rather grim", as Fung says in the story. It will rain but because we've cut down so many forests, altering the natural landscape that allows the water to cycle back into the atmosphere, much of it will fall in the middle of the ocean where we can't access it. This will result in widespread drought and famine in the not so distant future. Yikes. Being an environmental reporter in this day and age can be a bit disheartening.

So, I was curious how scientists like Fung and Dawson, whose research leads to predictions of widespread climatic chaos and environmental meltdown, are able to cope with their frequently depressing findings. And what do they hope to do with their results? Well, according to Todd Dawson and others on the Keck Hydrowatch team, this project can serve as a model for understanding water movement throughout the globe in order to more fairly allocate water for future human use in a dryer world. But also, and perhaps most importantly, this research can drive home the point that because climate change is largely the result of human activities, its solutions also reside with us.

Watch the "Tracking Raindrops" TV Story online, as well as find additional links and resources.

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I was reading out loud as we drove down I-64 towards an ever darkening sky. My friend, Brad shushed me at one point to concentrate on driving. I looked up to see why and was stunned. A sheet of water and staccato pulses of hail and lightning were all I could see. It reminded me of the intensity of being caught in blizzard conditions while driving toward Tahoe in Northern California. But here we were, in Virginia on a very warm and balmy day and the sky had literally opened up with water. What's more, hail was falling. I turned to Brad and asked how could hail exist in such warm conditions? He was stumped and I was fascinated.

With a little detective work, I came up with an answer to the dilemma. Hail is only produced in cumulonimbi clouds (thunderclouds). They usually only occur at the front of a storm system which was what we experienced. The hail hit in the first ten minutes and then was followed by heavy rain. However, the rain was warm to the touch unlike the frozen water making up the hailstones.

The fire in the nearby Great Dismal Swamp National Wildlife Refuge and incredibly hot and humid conditions in Virginia created ideal conditions for hail. Hail is created inside a thunderstorm that has strong updrafts of warm air and downdrafts of cold air. A water droplet with an apex point is picked up by the updrafts and travels into the cooler air and freezes. The apex point known as the condensation nuclei in the water droplet was probably dust from the fire or nearby salt water during this particular hailstorm. (Both Brad and I experienced dry and stinging eyes after going into one of the storms later that weekend, much like the stinging of salt water.) Layers of ice are then accumulated around this nuclei as the droplet goes through a cycle of being caught in an updraft and then carried beyond the freezing level of the atmosphere and then thawing partially in entering the warmer air on a downdraft. This cycle repeats itself creating increasing layers of ice. Then as some point this frozen water droplet with several irregular layers falls to the ground as hail.

Some of the largest hailstones have been recorded during summer storms in humid climates because the warm updrafts and cold downdrafts along with high surface heat create an optimal cycle for large hail. Smaller hailstones can be coupled more easily with larger hailstones in these conditions.

Video of Large Hailstones

Over the course of the weekend, we had three more thunderstorms (one of which broke a car back window nearby) and we kept an eye on a thundercloud that looked like it wanted to become a tornado. I came home very thankful for the fog! NOAA the National and Atmospheric Administration has a National Weather Service. At http://www.weather.gov/ anyone can check weather reports in any given area. To issue proper warnings and forecasts regarding hail, the National Weather Service uses a network of NEXRAD doppler radars to detect it. Hail size and probability can be determined from radar data by a computer by different algorithms and compared to the local atmospheric data to determine the threat level.

It seems the storms have not cleared yet throughout the area in Virginia we visited– severe thunderstorm warnings are still posted on NOAA. So the fireworks might have passed but thunderclouds are still lighting up the sky.

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