The Global Warming Debate Spectrum

March 24th, 2017

In the debate arena, the public likes simple narratives. If the narrative supports their pre-conceived notions, they like it even better.

On technical issues which have major public policy impact, however, the nuances can be very important even if they are not easily explained or grasped.

The scientific nuances in the climate change realm are abundant: How much of recent warming has been natural? We aren’t sure. Will clouds respond to warming in ways that make it worse, or lessen it? We aren’t sure.

In the global warming (aka climate change) realm, there is a spectrum of beliefs among the public, as the following chart shows:

Those who tend to view issues in black-or-white terms, and who don’t want to be bothered with understanding the details of the global warming debate, tend to gravitate to one or the other extreme. Which one they choose depends upon their worldview, or even their view of the role of government in our lives.

I’ve heard from people representing the opposite ends of the spectrum over the last 25 years in emails, claiming either increasing carbon dioxide in the atmosphere simply cannot affect climate, or claiming that we have pushed the fragile climate system past a tipping point and unstoppable warming, more severe weather, rapidly rising sea levels, death, destruction, and mayhem, are the inevitable result of our burning of fossil fuels.

I find it more than a little ironic that Greenpeace was basically forced to admit its own extremism of message in their defense against a defamation lawsuit in Canada that their extremist statements really can’t be taken as factual, but more as hyperbole.

It should be obvious that the truth lies somewhere between the two extremes in the above chart. That is sort of a trivial statement, though, without much value because it is so unhelpful in the policy realm since it covers a wide range of potential outcomes.

Policy changes depend partly upon our confidence in our predictions. If we are certain that in exactly one year a large asteroid will hit Earth, there would be a legitimate global effort to come up with a scheme for averting disaster, no matter the cost. But if there is a relatively small chance of it happening in the next 100 years, there might be little or no effort.

Costs versus benefits must also be addressed, including the impact of forcing more expensive energy on the poor through either legislation or EPA regulations. If it was relatively painless to switch to renewable energy sources, sure, do it.

But it’s not. Ask the countries that have tried.

Also, global greening in recent decades indicates more CO2 isn’t necessarily a bad thing. Crop productivity continues upward, even without planting more acres. 2016 saw record yields in corn, soybeans, and wheat. I’ve been a consultant with corn market interests for the last 6 years, and climate change isn’t even on their radar screen… except indirectly, since the ethanol mandate was supposedly intended to reduce CO2 emissions. It didn’t.

We see in the global warming policy arena there has been a gradual loss of public interest in doing something about global warming. A lot has happened since NASA’s James Hansen sensationally testified in Congress that he was mostly sure that the 1988 heat wave and drought were at least somewhat the fault of humans influencing the climate system.

Despite the initial alarm, in the last 20 years Gallup polling has shown that climate change has remained at the bottom of the list of environmental concerns among Americans. Except for the most recent survey results, there has also been a long-term downward trend over that 20 year period in how serious the public views the threat of global warming.

Why has the public lost interest? The reasons are many.

For example, most of the world’s population experiences many tens of degrees of natural temperature variation, yet they are asked to fret over two degrees of warming on time scales so long almost no one would notice it in their lifetime. The observed rate of warming has been about half of that predicted by the average climate model, and the climate model average is what guides energy policy.

Furthermore, the models do not produce realistic natural climate variability without considerable fudging and tinkering to fit the observed temperature record. As a result, we really aren’t sure recent warming isn’t partly or even mostly natural in origin. (Our study of ocean warming since the 1950s suggests about 50% each).

Finally, like the rock musician who is embarrassed to admit he actually likes ABBA, we are hesitant to admit we love our fossil-fueled transportation. We like the convenience of flying in jets. And the smaller cars get, the more pickup trucks we buy. Leonardo DiCaprio loves his yacht, I’m sure.

The polarization of the debate has led to a simplification of the narratives: you are either a denier if you tend toward the no-impact end in the above chart, or an alarmist if you tend toward the dangerous impact end of the spectrum. Judith Curry has written a lot about the polarization of the debate in the years since the Climategate email release pushed her into the skeptic camp.

In the quarter century I have studied this issue, I dont think we are much closer to having an answer to just where the climate system will end up. Just about anything is theoretically possible. The science is much more difficult than putting a person on the Moon, which was basically just an engineering exercise involving man-against-gravity, and making sure he has air, food, and water for several days.

Nevertheless, a little-known hint of what direction the science might be going is the fact that the latest U.N. IPCC report (AR5), which historically tends toward the alarmist extreme (at least in its Summary for Policymakers) has lowered the lower limit of warming to about 1 deg. C for a doubling of atmospheric CO2. (How could this be, you ask, if weve already experienced about 1 deg. C of warming without CO2 doubling? Because there could be natural warming influences causing a substantial portion of observed warming.) Admittedly, they consider 1 deg. C to be extremely unlikely. If I had to choose a number, I’d go with about 1.5 deg. C, but they consider that unrealistically optimistic as well.

The fact that our satellite observations have shown less warming than the surface, rather than more warming as would be expected theoretically is another hint that the theory encapsulated in the models has a serious bias. The most obvious potential reason for this is that water vapor feedback is not as strong in reality as in the models, since those models with the strongest positive water vapor feedback also produce the strongest amplification of warming with height in the troposphere.

My opinion tends toward the little-impact end of the spectrum. I suspect that future warming will be slow and relatively benign (say, 1.5 deg. C by the end of this century), severe weather events won’t become demonstrably worse, and slow sea level rise will continue roughly as it has for centuries. People will adapt to whatever slow changes occur.

And renewable energy (or maybe safer nuclear energy) breakthroughs will come from the private sector and market forces, not from legislative fiat.

While climate science will continue to try to nail down just where we are in the spectrum of climate impacts, what we hear in the news media will continue to veer toward the ends of the spectrum, with exaggerated claims from opposing tribes, based upon fears and click-seeking more than on evidence. Heat waves, freezes, floods, droughts… these events make news, just as they have throughout recorded history. Average weather does not. We lukewarmers will continue to be lost in the noise.

I suspect we will not have much more scientific confidence ten years from now. A lot will depend on where global temperatures go from now on, because the science will just remain too uncertain until Mother Nature shows her hand.

Congressional hearings into climate issues, put on mostly for show, will continue to pit competing views against one another. As usual, the opposing views will largely cancel each other out, despite each of the tribes claiming victory.

And the wheels on the bus go round and round.

The Russians Hacked our Winter Weather

March 23rd, 2017

Now that winter has officially ended, I thought it would be useful to address the central role that Russia played in ending California’s drought, as well as in the unusually warm conditions over the eastern U.S. this past winter.

First, let’s address the record California rains and mountain snowpack. While such a wet winter usually requires a strong El Nino, we had just the opposite — a weak La Nina.

So, what happened?

California: The “Atmospheric River” Doesn’t Explain It

Blaming the wet winter in California on the “atmospheric river” effect is, in my professional opinion, rather lame. It’s like blaming a flash flood on “too much water”. Well, duh.

So, what caused the atmospheric river?

A persistent series of extratropical storms (low pressure systems) coming into California.

But what caused the storms?

An enhanced temperature contrast between the tropics and mid-latitudes, always required for the formation of such low pressure systems.

But what caused the enhanced temperature contrast?

It wasn’t El Nino, the usual culprit in stormy California winters, because we had the opposite — La Nina.

It was because our winter was hacked by the Russians

It all started back in October, 2016. (Before the election! A coincidence? I think not.)

October experienced an unusually rapid buildup of the cold season air mass in Siberia, as seen in this temperature departure-from-normal map (all maps courtesy of

By November, those unseasonably cold air masses were traveling across the North Pacific, cooling the upper layers of the ocean, and turning the previous Warm Blob of sea surface temperatures into a Cold Blob:

This set up a stronger-than-normal temperature contrast zone (“baroclinic zone” to us meteorologists), which is what’s necessary for extra-tropical storm formation. The temperature departures from normal for the winter months of Dec-Jan-Feb reveal the persistence of this feature, which then led to repeated formation of low pressure systems and the warm, moist flow of air out ahead of those lows as they tracked eastward:

The unusual warmth of the eastern U.S. was likely the result of this chain of events as well. The process has now ended, but not before the cherry blossoms in D.C. were fooled into coming out early, and then the Canadians with their own flavor of frigid air swooped in and ruined everything about a week ago.

So, I suggest it’s time for congressional inquiries into the pre-election Russian hacking of our winter weather.

Brace Yourselves: Snowstorm to Breed Global Warming Hysteria

March 13th, 2017

With apologies to Benjamin Franklin, only three things in life are certain: death, taxes, and blaming bad weather on global warming.

By mid-week this week, newspaper and website stories will be reporting that climate experts (e.g. Al Gore, Bill Nye) have now blamed the historic snowstorm and unseasonable cold now descending on New England on climate change.

I suspect a few of these experts already have their tweets composed, just waiting for snow totals to exceed one foot.

Indeed, the latest GFS model forecast shows that by midday Wednesday some rather spectacular snow totals will have probably accumulated, from the DC area through Philadelphia, NYC (maybe 20 inches there), and Boston (graphic courtesy of

The Nor’easter and cold temperatures will be blamed on the same climate change that caused the unusual warmth over the eastern U.S. over the past couple months.

Global warming theory is in fact so malleable that it predicts anything. More cold, less cold. More snow, less snow.

What a powerful theory.

And what’s even more amazing is that climate change can be averted by just increasing your taxes.

But what nobody ever reports on — because it would be boring — are the storms and severe weather events that haven’t happened. For example, U.S. tornado counts have been running below average, or even at record lows, in recent years.

Amazingly, the low tornado activity has been blamed on climate change. So, too, have actual tornado occurrences!

What a grand and gloriously useful theory global warming provides us.

Is it any wonder that the public tends to be skeptical of what the experts tell us, when those experts continually change the narrative as their forecasts turn out wrong?

Winters in the U.S. are notoriously variable. Typically, if it’s warm in the East, it’s cold in the West. This is exactly what has happened this winter, except for this brief reversal before winter’s end.

Normal people call it weather. More enlightened people, in contrast, call it climate change. Next winter it could be the opposite. No one knows.

Like death and taxes, though, what is certain is that anything “unusual” that happens will somehow be blamed on your SUV.

UAH Version 6 Dataset Paper Published Online

March 7th, 2017

At long last, our Version 6 dataset paper has been published, with the online version available as of today:

UAH Version 6 Global Satellite Temperature Products: Methodology and Results

We have been working with NCEI (old NCDC) to get the dataset and code archived there (contrary to some claims, our Version 5.6 dataset and code have been archived there for years). This takes time as NCEI has procedures, review meetings, etc., before they can host a dataset and code.

(I can download the PDF…maybe someone can tell me if it’s publicly available, too.)

UPDATE: Since the paper is paywalled, here’s our final submitted version.

UAH Global Temperature Update for February, 2017: +0.35 deg. C.

March 2nd, 2017

The Version 6.0 global average lower tropospheric temperature (LT) anomaly for February 2017 was +0.35 deg. C, up a little from the January value of +0.30 deg. C (click for full size version):

The global, hemispheric, and tropical LT anomalies from the 30-year (1981-2010) average for the last 26 months are:

2015 01 +0.30 +0.44 +0.15 +0.13
2015 02 +0.19 +0.34 +0.04 -0.07
2015 03 +0.18 +0.28 +0.07 +0.04
2015 04 +0.09 +0.19 -0.01 +0.08
2015 05 +0.27 +0.34 +0.20 +0.27
2015 06 +0.31 +0.38 +0.25 +0.46
2015 07 +0.16 +0.29 +0.03 +0.48
2015 08 +0.25 +0.20 +0.30 +0.53
2015 09 +0.23 +0.30 +0.16 +0.55
2015 10 +0.41 +0.63 +0.20 +0.53
2015 11 +0.33 +0.44 +0.22 +0.52
2015 12 +0.45 +0.53 +0.37 +0.61
2016 01 +0.54 +0.69 +0.39 +0.84
2016 02 +0.83 +1.16 +0.50 +0.99
2016 03 +0.73 +0.94 +0.52 +1.09
2016 04 +0.71 +0.85 +0.58 +0.93
2016 05 +0.54 +0.65 +0.44 +0.71
2016 06 +0.34 +0.51 +0.17 +0.37
2016 07 +0.39 +0.48 +0.30 +0.48
2016 08 +0.43 +0.55 +0.32 +0.49
2016 09 +0.44 +0.49 +0.39 +0.37
2016 10 +0.41 +0.42 +0.39 +0.46
2016 11 +0.45 +0.40 +0.50 +0.37
2016 12 +0.24 +0.18 +0.30 +0.21
2017 01 +0.30 +0.27 +0.33 +0.07
2017 02 +0.35 +0.54 +0.15 +0.05

The slight warming in February came from Northern Hemisphere land areas. The tropics have cooled by about 1 deg. C from the peak El Nino warmth of 1 year ago.

The UAH LT global anomaly image for February, 2017 should be available in the next several days here.

The new Version 6 files should be updated soon, and are located here:

Lower Troposphere:
Lower Stratosphere:

Fan Mail

February 18th, 2017

Once in a while I share “fan mail” I get in response to my blog, and I thought the following example was unusually interesting.

I won’t bother to rebut the mix of misrepresentations, misinformation, etc. This is more for entertainment value.

WARNING: The language in the following is, shall we say, colorful. Don’t read any further if you are easily offended.


Like every other idiot who thinks 7.4 billion human beings cannot alter our planet, you fail to ask yourself the most important question you should be asking: what if you’re wrong.

If you are wrong, and mankind is desequestering carbon, nitrogen, and hydrogen in the form of fossil fuels, then you are advocating the destruction of humanity through the reversal of natural climate engineering.

If you’re wrong and we continue to use fossil fuels, the species and all other mammals will be forever wiped out.

And you are so fucking arrogant, and so fucking lazy, as to not bother asking that simple question.

Why? Because it would be too much work for you to live without your fucking car.

Fuck you.

Go do your fucking homework asshole. Your “science” can’t explain the CO2 levels in the atmosphere, nor the melting Arctic ice cap, nor even why the ice ages occurred only in the northern hemisphere. You don’t understand a damn thing about weather or climate, or even basic atmospheric chemistry. All you know is your fucking ego.

Well, asshole, I’m not impressed by your ignorance, your stupidity, nor your arrogance.

How about this, asshole, tell me how much WATER has been brought up from fossil fuels, how much carbon, how much nitrogen, how much oxygen, and what percentage they increased their corresponding partial pressures in the atmosphere.

Then tell me what the climate was like when the atmospheric carbon was as high as it is now, and whether or not mammals existed.

By the way, asshole, The Oroville Dam is NOT a simple earthen dam, it is a SYSTEM, and that SYSTEM, including the concrete reinforced auxiliary spillway, has failed, because the system was designed to control the flow of water, and right now, there is no such control, and there are processes in place which are destroying the FOUNDATION of the auxiliary spillway and significantly reducing the capacity of the lake to hold water, and which is now presently flowing quite quickly down the mountain.

I hope someone believed you, loses their home, and sues your ass, and takes your bullshit global warming denial into court to demonstrate just how harmful your bullshit is.

You’ve probably killed people downstream, which is no surprise coming from a man who advocates the self-destruction of the human species.

Trust me, the species would do a lot better without ignorant, arrogant assholes like you.

Oroville Dam: Crisis Eases, Emergency Spillway Repairs in Progress

February 15th, 2017

With the evacuation order lifted last evening, and ~185,000 residents returning to their homes in Oroville and surrounding communities, emergency repairs continue around the clock on the damaged emergency spillway at Oroville Dam. Yesterday morning (Feb. 14), a concrete pumper and boulders were being used to patch the main erosion features that developed when the emergency spillway was overtopped:

The water level of the lake is being reduced by 8 or 9 feet per day, and now stands at 880 ft., which is 21 feet below the top of the 901 ft.-elevation concrete weir that was overtopped a few days ago by 1.5 ft. The rapid lowering of the lake is being accomplished with a continuous 100,000 CFS flow over the main spillway (the same as the average flow over Niagara Falls) which was heavily damaged over a week ago:

Little more than one day of only about 10,000 CFS flow over the concrete weir of the emergency spillway caused unexpected erosion down into the highly fractured bedrock, which is what led to the evacuation orders as the continuing erosion back to the concrete weir led to fears that structure could be compromised:

I’ve been following a continuing discussion by outside experts here, and also following the forecasts of a series of new storms that will sweep through California over the next week.

Based upon everything I’ve seen, I’d say that for the foreseeable future, the dam facility is out of danger. Here’s why:

1) The 100,000 CFS flow through the (damaged) main spillway will, in all likelihood, keep the lake level below the 901 ft. elevation of the emergency spillway. Even though the next week of storms will cause as much as 7-14 inches of liquid-equivalent precipitation to fall, much of that will fall as snow except over a relatively small portion of the watershed. The 100,000 CFS flow rate through the main spillway could be increased to 150,000 CFS if needed.

2) As of yesterday, the main spillway damage was not eroding uphill, suggesting that portion is on bedrock. It is possible that the remaining concrete is actually more stable at higher flow rates, which creates a waterfall out and away from the bedrock the concrete flume is sitting on.

3) Spring snow melt usually occurs slowly enough that the main spillway will be able to keep up with it.

4) Even if the concrete weir is over-topped again, and erosion of the bedrock extends back to the concrete weir, that structure is very thick, and it is not at all obvious that it would fail. This is a big uncertainty, though, and if it ever gets to that point, evacuations would again be announced.

Note that all of this positive outcome depends upon the undamaged uphill portion of the main spillway remaining stable. This is why repairs to the hillside below the emergency spillway are being performed as fast as possible, in case the main spillway fails and the lake level rises uncontrollably, and then once again overtops the emergency spillway weir.

I believe that the use of the previously-untested emergency spillway, and the resulting damage, was actually a blessing in disguise. That structure was designed to handle 10-15 feet of water flowing over it, but it only took 1.6 ft of flow to cause substantial hillside erosion in less than 2 days. Now that the geology of that hillside has been revealed, engineers will be able to come up with an engineering solution so that if there ever is a catastrophic flooding event, the emergency spillway will be in a much better state to handle it without failure of the concrete weir, which could result in a ~30 ft. wall of water to cascade downstream.

The Oroville Dam Crisis: What Happened, What’s Next?

February 14th, 2017

After watching the Oroville Dam crisis evolve over the last several days, and reading various experts’ opinions about what might be going on both with both the facility itself and behind the scenes decision-making, I thought it might be time to step back and discuss where we are at, and where we might be going.

The Dam Spillway Situation

First of all, the immediate crisis has passed. At this writing (4 a.m. PST Tuesday), the lake level has been lowered to 11 feet below the emergency spillway, and is dropping at a rate of about 8 feet per day. The goal is to get it to about 50 feet below the top of the concrete weir of the emergency spillway, which was topped by 1.5 feet at the peak of the crisis.

That’s the good news.

The bad news is that in order to achieve this, the flow through the main concrete-lined spillway, which has been heavily damaged, has had to be increased to 100,000 cubic feet per second (CFS), creating a spectacular waterfall over the lip of the remaining portion of the concrete flume:

More on that later.

The other bad news is that the relatively brief use of the emergency spillway led to a lot more erosion into the rock below the concrete weir than engineers expected. This rapid erosion is why evacuations were suddenly ordered, since there were fears that it would backcut to the concrete weir, which was at risk of collapse:

One of two major eroded areas just below the emergency spillway of Oroville Dam (Feb. 13, 2017).

If that happened, a 30 ft. wall of water would cascade downstream. At least two large gouges are currently being patched with sacks of rock and some concrete. The emergency spillway was supposedly designed to handle 350,000 CFS, but it only took a day at 10,000 CFS to cause the damage, leading up to an official warning that the spillway could collapse within an hour and the mandatory evacuation order. (The main earthfill portion of the dam is in no danger, since the emergency spillway, 20 ft. below the level of the main dam, would keep the main dam from ever being topped).

My (admittedly non-expert) view of the situation is that the emergency spillway is of lesser concern at this point. Rains will return Wednesday night beginning a 7-day wet period during which 5 to 12 inches of water-equivalent precipitation will fall on the watershed:

Google Earth view of the watershed feeding Oroville Lake. Much of this area is above 4,500-5,000 ft. elevation, where winter precipitation usually falls as snow.

That might sound bad, but the good news is that most of that precipitation will fall as snow, except over the lake itself, in contrast to earlier warm rain events that led to the current crisis.

Despite the new precipitation, I suspect that they will be able to keep the lake level to around 850-860 feet or so, which is 40-50 feet below full-pool. It might briefly rise by 10-20 feet if the rain is exceptionally heavy. The main danger to Northern California dams is heavy rain events; spring snow melt typically occurs more slowly and is easier to handle by adjusting outflow from reservoirs.

I further suspect that concern will be shifted to the main spillway, the continuing heavy use of which is absolutely required in order to keep the lake level low enough to allow repairs to the emergency spillway, as long as there is significant runoff into the lake.

Close-up of damage to main spillway on Feb. 7; the concrete wall in the foreground has since been destroyed with considerable erosion of the adjacent hillside (SacBee photo).

The hydro plant generators have been shut down from debris, and they would have only allowed an additional 16,000 CFS outflow anyway. The diversion tunnels were damaged years ago and are unusable.

So, the damaged main spillway is essentially the only way that the reservoir can shed substantial volumes of water as rains occur, and as spring snow melt begins.

I predict that they will shut the main spillway down soon to see how fast the damage is eroding uphill. If I had to guess, I’d say that shutdown might actually happen today…a three hour shutdown will only reduce the lake level fall by 1 foot. They need to assess the situation, because…

A PR Disaster is Rapidly Approaching

From watching the daily press briefings, I think that the experts and emergency officials have been less than forthcoming on details. As dam expert Scott Cahill wrote yesterday, the public has been treated a little like children so far. Reporters’ questions have gone unanswered, and the experts opinions have careened between “no danger” and “imminent failure” in less than 24 hours. (Update: Scott Cahill has a new essay today about how no one is ever accountable anymore in disaster situations…it’s all review panels and committees….the buck is passed from person to person until no one knows who has the buck.)

This is NOT the way for “experts” to engender confidence in the public.

Of particular concern is the estimated 185,000 residents who have evacuated to higher ground, and are anxious to return to their homes. We live in an age where we want results now, and the longer these people have to wait with only general information being provided, the more anger and frustration will grow. Reporters are going to cover this frustration, with face-to-face interviews, and officials had better get ahead of the impending PR disaster while they can.

When will people be allowed home? I can only speculate. If emergency officials are being very cautious they might wait until the coming wet weather period has passed, which would be at least 10 days to make sure the lake does not rise too much, and until after they have verified the concrete flume of the main spillway isn’t eroding uphill very much.

Or, they could let people return at any time, warning them to keep alert for a possible future evacuation with little notice. I really dont know. If I had to guess, I’d say they will go the cautious route. But if they were to inspect the main spillway today and see only minor additional erosion uphill from where it previously was, maybe they will let people come home very soon.

No matter what happens in the coming days and weeks, Oroville Dam will remain an issue for months — maybe even years — to come. Repairs will be expensive and lengthy. And there will be second-guessing of decisions made, including the 12-year old report by experts that the emergency spillway was just fine as-is.

(A detailed chronological discussion of the Oroville issues by mainly geologists, along with some amazing photos, can be followed here.)

UPDATE: Mick West, Sacramento, provided this graphic which shows the volume of water that can be output from Lake Oroville at 100,000 CFS flow through the main spillway (area of the red box), versus what has flowed into the lake from precipitation in the last couple months (area under the blue curve). It suggests that the lake can probably be kept from completely filling again if 100,000 CFS outflow is maintained, with only temporary rises in lake level after heavy rain events:

Drone video of emergency spillway damage from evening of Feb. 13, 2017 (CA DWR).

Oroville Emergency Spillway: Does this Look Like Bedrock to You?

February 13th, 2017

I’ve had a little criticism here and on Facebook that I’m not a geologist, so I shouldn’t be second-guessing the Oroville Dam engineers. They called for evacuations last evening out of an abundance of caution. That the emergency spillway is no doubt built on bedrock, and so it is safe.

Well, if it was only out of an abundance of caution that evacuations were ordered, why did emergency officials claim that there might be only one hour until the concrete weir topping the emergency spillway would fail? Hmmm?

And take a look at one of the ravines that eroded from only a little over 24 hours of flow over the emergency spillway

One of two major eroded areas just below the emergency spillway of Oroville Dam (Feb. 13, 2017). The little yellow spots are people.

Does that erosion feature look like it’s cutting into bedrock? Even though the spillway is supposed to handle 250-350,000 CFS, it was only ~10,000 CFS total flow across the 1,700 ft. long weir that caused this.

The latest press conference held shortly after noon today suggested that officials are avoiding hard questions. At one point a reporter asked, “With two parts of the system compromised (the main spillway and emergency spillway), how secure can people be?“. The speaker was not allowed to answer the question.

I honestly don’t know what’s going on, but if I lived in the flood plain (and now one of the near-200,000 people evacuated), I’d be wanting some more definitive information.

Oroville Dam Emergency Spillway Repairs Starting

February 13th, 2017

With daylight and Oroville Lake water levels now 4 feet below the lip of the emergency spillway, we can see that the area of concern is a gouge which developed near the far end of the concrete weir, and was eroding uphill toward that structure; for scale, those yellow spots are people inspecting the gouge (click images for full-size):

A wide-angle view (KCRA-TV helicopter frame grabs) shows the main, heavily damaged spillway which still has a huge 100,000 CFS flow continuing in an attempt to reduce the lake level as much as possible:

Rocks have been bagged overnight and helicopters will soon start filling the gouge:

The 100,000 CFS flow through the main spillway continues to erode the break in the concrete flume, but engineers are not worried about the damage eroding uphill and damaging the main portion of the dam: