Tag Archives: Ad Hoc Reasoning

After-the-fact reasoning: after something happens, pulling out an explanation which is based entirely on already knowing what happens.

All gone by the year 2020: some justifications for why the prediction failed

This is part 2 in the series on the prediction that glaciers in Glacier National Park will be gone by 2020. You might want to see to part 1 if you haven’t already

There are some efforts to explain the failed “gone by the year 2020” prediction. These are however more difficult to find because they are so sparsely distributed and not to be found in the media, this contrary to the emotional “gone by the year 2020” claim that was broadcast and shared widely.

I found two justifications for the failed prediction. The first one is a paragraph on a webpage of the National Park Service dedicated to melting glaciers (emphasis by the National Park Service):

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“Unprecedented”, “Unprecendented?” or just reasoning after the facts?

Besides argument 4, which was the subject of last post, there were ten others. I am not going through the whole list, this is probably (one of) the last in this series. Argument 1 is also equally puzzling. Although I have no problem with the arguments as such, these are worthless in “tearing down” the Washington Post article.

I first wanted to write this as an update to a previous post, but it became much longer than I anticipated and I elevated it to this post.

Here it is (emphasis by the author):

1. The use of the word “Unprecedented.” versus “Unprecedented?”. In my original website post on Wednesday June 29th at 1:46 am EST, and in my YouTube video I used the title “Unprecedented, Jet Stream Crosses the Equator”. I quickly realized that one should really “Never say never” and “Never say always”. Thus, I corrected this erroneous title on my website post later that same day, on Wednesday June 29th at 1:36 pm; and also shortly after that on my YouTube video to “Jet Stream Crosses the Equator, Unprecedented?”. When the Washington Post article came out the next day at 12:43 pm on Thursday June 30th, almost a full day after my title correction, it unfortunately remarked on my original title, and not on my corrected title. I intended to be asking a question, namely, was the movement of the jet stream perpendicular to the equator a new behavior? I was not intending on claiming that it was new, but was asking the question since it seemed to me to be very unusual. Equatorial monsoon winds crossing the equator at relatively low wind speeds are known to occur, but they usually involve wind directions only a few degrees from the equator axis, and not at a 90 degree angle (perpendicular). The behavior that I described in the video seemed very different to me, than that of monsoonal winds.

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“Climate science educator”: we no longer have this stable, predictable system that we had…

jetstream crosses equator scream

Looking at the story about the cross-equatorial flow and the subsequent declaration of an emergency, I became curious about the Beckwith video that would give more explanation. Watching it was quite an experience. This is what he said after introducing himself:

For many years I have been talking about abrupt climate change and how the climate system is no longer behaving like it used to. We no longer have this stable, predictable system that we had. We gone to a chaotic system. As we transition in a non-linear fashion to a warmer world, we see a complete redistribution of jet streams and ocean currents.


I did’t expect something like that from someone who calls himself a “Climate System” scientist. The climate system, being a complex, coupled, chaotic system, is by its very nature unpredictable. How could he think that it ever was stable and predictable before?

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Global warming politics explained in 2 minutes

While in Europe winter temperatures were very balmy, the United States plunged into a deep freeze and skeptics were having a field day. The United States government was apparently not amused and made a video, starring John Holren, to assure the public that global warming is still there. The video is called “The Polar Vortex explained in 2 minutes” and it starts like this:

If you have been hearing that extreme cold spells, like the one we are having in the United States now, disproves global warming, don’t believe it.

Logically I can agree with that. A cold spell doesn’t disprove global warming, although this statement is not a big deal anyway. But I don’t think it is used this way in this video. Probably the author meant to say something like this: “global warming is still true, despite the cold snap, so don’t believe those who question it”. But global warming still being a theory, it is something that can’t be proved nor disproved yet. A single weather event can not disprove it, but when it is contradictory to the theory, it can weaken its case.

It continues:

The fact is that no single weather episode can either prove or disprove global climate change. Climate is the pattern of weather that we observe geographically and over the seasons and is described in terms of averages, variations and probabilities. But a growing body of evidence suggest that the kind of extreme cold being experienced by much of the United States as we speak, is a pattern that we can expect to see with increasing frequency as global warming continues.

Also here, indeed, I can agree that a single weather episode can neither prove nor disprove global climate change. Yet this new event is promoted to climate…because there is a growing body of evidence that suggest this pattern is expected to increase when global warming continues.

See the carefully change from global warming to “global climate change”, whatever that means. Climate changes all the time and there is not one global climate as there is not one global temperature. That seems replacing one meaningless term by another. Why the shift? Probably because global warming sounds a bit silly in the face of 12-17 years of no global warming.

Now this cold spell that was portrayed a couple sentences ago as a single weather event is suddenly a pattern? How many times such a similar event happened in the last decade or so? It surely doesn’t prove anything, but promoting it to something that is going to happen frequent in the future on basis of an accumulation of assumptions is a bridge too far.

And the reason is this: in the warming world that we’re experiencing the far north, the Arctic, is warming roughly twice as rapidly as the mid latitudes, such as the United States. That means that the temperature difference between the Arctic and the mid latitude is shrinking. And that temperature difference is what drives what is called circumpolar vortex, which is the great counterclockwise wise swirling mass of cold air that hovers over the Arctic. As the temperature difference between the Arctic and mid latitudes declines the polar vortex weakens and it becomes wavier. The waviness means that there can be increased larger excursions of cold air southward, that is into the mid latitudes. And in the other face of the wave increased excursions of relatively warmer mid latitude air in the far north.

What struck me is the mixing of “global and “local”. He definitively uses global warming/global climate change to describe the process, but if you read it carefully it is not about global warming at all, but about LOCAL warming! It is the warming of the Arctic, twice the rate of the mid latitudes. That is not global warming, that is local warming. And how can GLOBAL warming increase cold patterns when the global temperature didn’t change in 12-17 years and the pattern is dependent on LOCAL warming?

Computer models tell us that there are many different factors influencing these patterns. And as in all science there will be continuous debate about exactly what is happening. But I believe that the odds are we can expect, as a result of global warming, to see more of this pattern of extreme cold in the mid latitudes and some extreme warmth in the far north.

Couldn’t help chuckling when hearing the “computer models tell us” phrase. What he didn’t want to say is that computer models have it difficult to model these patterns. What he also didn’t tell with that many words is that not all different factors are known yet. He unveils it a bit in the next sentence in which he states that there is a continuous debate about what is happening (not with skeptics I think) and also he believes that the odds are that we can expect more of these things. Hey, but that is suddenly something different. He is not sure, but maybe, just maybe, this could be true. Or not.

But not only the words are important, what is being seen is as well. Let’s look at the first thing in the background that caught my eye:

Polar vortex in 2 minutes video sceencap

Polar vortex in 2 minutes video sceencap – hurricanes?

Are this the tracks of hurricanes? What are they doing in this video? Sure, it has being said that hurricanes are on the increase because of global warming, but observational evidence is stacked against this. So do they want to keep the suggestion that hurricanes are still a threat?

Polar vortex in 2 minutes video sceencap

Polar vortex in 2 minutes video sceencap – Glowing earth

And what is it with the red glowing earth? Europe, most of Asia/Russia and almost complet of Africa has a close to maximum anomaly of somewhere around 5 – 6 °C? And do I see it right that the North Pole region is blue?!?! That is contrary what Holdren was telling all along. I don’t know any dataset with 5-6 °C anomaly in such large regions. Is this the result of a model?

Polar vortex in 2 minutes video sceencap

Polar vortex in 2 minutes video sceencap – Sea ice extent

Of course the mandatory Arctic sea ice … until 2012! We are in 2014, The data of 2013 should already known. Looking for the source, it seemed that NASA is the source for the graph and animation (see “Arctic Sea Ice”). It is the annual Arctic sea ice minimum area from 1979 to 2012. Looking further they seem to mix area with extent and omit that the data is about the yearly minimum extent. They got their data from NSIDC (which uses extent, not area). In 2012 the extent was indeed 3.413 million km2. In 2013 the lowest extent was 5.103 km2 on September 16, 2013. This makes the omission of the data point of 2013 even worse: the minimum extent of 2013 at the time of the video is already known for almost 4 months!

So being curious, when drawing the minimum extent of 2013 on this graph we get this:

Polar vortex in 2 minutes video sceencap

Sea ice data + added extent of 2013 to the graph

That is not really convenient when one tries to explain that this cold snap was caused by the Arctic ice melt. That obviously didn’t melt as much as the last years and now on the level of 2005.

Again being curious, I found an animation of the Arctic Ice extent in September 2013 by NASA and made a screenshot of the extent of September 12, 2013 (a few days before minimum extent):

Arctic Ice extent on September 12, 2013 Source: Nasa

Arctic Ice extent on September 12, 2013
Source: Nasa

Quite a diffence when one compares it with low 2012 extent from the video. It is obvious they couldn’t possibly show that. It wouldn’t advance their cause.

The video shows us that the voices of those who question global warming start getting threatening to the party line. That became so uncomfortable that they had to do something. Like making a video. Questioning the party line, we can’t have that, can’t we?

The polar Vortex doesn’t disprove global warming. Sure, but that is no big deal actually.

There was lots of talking about the polar vortex this week. Even in this tiny country, which wasn’t affected by the freezing temperatures (yet), the media was full of the polar vortex that made the freezing temperatures in Northern America possible. The media was assuring us that this cold snap was the result of global warming (but a lot carefully avoided calling it global warming and diplomatically called it climate change).

This is basically how the media said it works: it is the result of the rapid melting of Arctic sea ice because of climate change. This decreases the albedo of the Arctic region and as a result it heats up faster than other parts of the Earth. The temperature difference between the Arctic and the southern regions determines the strength of the jet stream. If the jet stream is strong, it isolates the cold Arctic from the warmer mid latitudes. But because of this melt the jet stream becomes weaker and more wavy, allowing cold air (usually confined to the poles) to reach further into the mid latitudes. Et voilà, global warming/climate change caused the severe cold snap. John Holdren, the science advisor of President Obama, even went that far to state that because of this process those deep freeze cold snaps will occur more frequent in the future.

But in general, I can agree with the statement that current cold wave doesn’t disprove global warming. Yet, while it is a nice explanation of the assumed mechanism, it doesn’t prove global warming either. It only proves that media and scientists are creative in finding new ways to fit new events into the theory. AFTER the facts, that is. That’s not difficult, that is what humans are good at, finding connections between seemingly unconnected things.

But deep freeze winters due to the weakening of the jet stream is nothing new. In the 1970s it was used to explain the coming of a new ice age. Younger people may think the weather we see now is unprecedented, but it is not that extreme, nor unprecedented when looking at it over a larger time frame. Remove the hype and there is not much of a story left. Holdren, as a crusader of the coming new Ice Age in the 1970s, should at least recognize that.

How much of this is due to anthropogenic causes? The theory seem to rely on polar amplification. That is a real process, but it doesn’t prove anything about the anthropogenic nature of the warming. Any warming would have that effect, whether it is natural, anthropogenic or both. By the way, the outbreak of cold is also part of the negative phase of the Northern Atlantic Oscillation, which is a natural pattern.

To me it seems yet another patch on a wound of a heavily bruised theory that continue to limp further. I didn’t hear anything about having a higher frequency of very cold winters as a result of global warming/climate change until recently. On the contrary. I heard a lot about more heatwaves, higher temperatures at night, more droughts, more storms, less to no snow,… sure, but very cold winters? No. When it started to snow massively in 2010, suddenly snow became a result of global warming or at least not impossible in a warming world. It seems the same with the cold winters due to the melting ice. Just adding to the possible explanations and covering an additional hole without elimination other ones.

I would be more impressed if scientists came with new falsifiable hypotheses/predictions (based on the global warming theory) about these snowy winters. Now we only hear after the facts that this is not impossible in a warming world or doesn’t disprove global warming. Which is not a big deal actually.

Chilling lesson from the past


When hearing about the “global warming creates cold weather”-ad hoc explanation for our cold winter/spring, it all seemed familiar to me. I definitely heard that before. In the 1970s this was also how the coming Ice Age was explained. For example, this is how Science News brought it in 1975:

The principal weather change likely to accompany the cooling trend is increased variability-alternating extremes of temperature and precipitation in any given area-which would almost certainly lower average crop yields. The cause of this increased variability can best be seen by examining upper atmosphere wind patterns that accompany cooler climate. During warm periods a “zonal circulation” predominates, in which the prevailing westerly winds of the temperate zones are swept over long distances by a few powerful high and low pressure centers. The result is a more evenly distributed pattern of weather, varying relatively little from month to month or season to season. During cooler climatic periods, however, the high-altitude winds are broken up into irregular cells by weaker and more plentiful pressure centers, causing formation of a “meridional circulation” pattern. These small, weak cells may stagnate over vast areas for many months, bringing unseasonably cold weather on one side and unseasonably warm weather on the other. Droughts and floods become more frequent and may alternate season to season, as they did last year in India. Thus, while the hemisphere as a whole is cooler, individual areas may alternately break temperature and precipitation records at both extremes.

Indeed, very familiar when comparing what is proposed now as the reason for the current cold weather. Just somewhat different word preference. Read “Jet stream” for “upper atmosphere wind patterns”, “positive phase” for “warm periods”, “negative phase” for “cooler periods”, “Blocking” for “Stagnate”.

What were/are the effects:

  • Increased variability: check.
  • Alternating extremes of temperature and precipitation. Broken up into irregular cells. Check.
  • May stagnate over vast areas for many months, Check.
  • Unseasonably cold weather on one side and unseasonably warm weather on the other, Check.
  • Droughts and floods become more frequent. Check.

These effects are not unusual for a negative phase of the Arctic Oscillation. The Arctic Oscillation was predominantly positive for the 1980s and 1990s, which had an influence on the winters in the Northern Hemisphere. One time or another it was bound to go negative again. So how can one differentiate clearly between the two when the explanation has the same effect as the natural variation? Not to mention the scientists were surprised and had to again rebuild their theory to match the new observations.

The name of the phenomenon “Arctic Oscillation” is not used because at that time the phenomenon didn’t have a name yet. It was given by Wallace and Thompson at the end of the 1990s, who seem to consider it a natural process. In the current explanations of the warm cold, the name is not stated either, probably for other reasons.

This is how they showed it graphically in 1975:

Source: Science News: Climate Change – Chilling possibilities

Compare it with current graphics:

Source: http://www.ees.rochester.edu/fehnlab/ees215/

So the same process seemed to be used to explain two opposites. In the 1970s to explain it was colder and we might go towards a new ice age. Now to explain global warming is still here and hey, it is getting colder because of “global” warming.

The incredibly morphing theory


When reading the first statement from the dossier of the Flemish greens I had the impression that the author avoided to name of the phenomenon he described. When reading the next two statements I had the exact same impression. They were made by investigators of the Potsdam-Institut für Klimafolgenforschung (PIK) who cited two studies about atmospheric changes. They describe the impact of the Arctic Oscillation on our weather, but carefully avoided its name. In stead they make the “suggestion” that global warming (by warming the Arctic region) changes these “waves” and therefor was (partly) the cause wintry weather we got.

The first statement is from Jaiser et al. The second from Petoukhov et al. I could trace this last one back to: Weather extremes provoked by trapping of giant waves in the atmosphere by Petoukhov et al.

They seem to explain the cold weather by blocking events in the higher atmosphere partly caused by the warming of the Arctic. I could agree with the blocking event causing our rather cold weather. As far as I can know it was seen as the common cause for the heat wave in Russia 2010, the Pakistan flood in 2010 and the heat wave in the United States in 2011. I think it is a known meteorologic process.

What about the human attribution?

[…] the suggested physical process increases the probability of weather extremes, but additional factors certainly play a role as well, including natural variability. […]

To be fair, they say it increases the probability of extremes and that natural variability plays a role. In the paper they calculated the wave motions and tested when they grind to a halt of amplify. Okay, but this part catched my attention (my bold):

[…] Also, the 32-year period studied in the project provides a good indication of the mechanism involved, yet is too short for definite conclusions. […]

A 32 year period (the research was sent for review in June 2012) means the start of their investigations was around 1980. Just at the beginning of a warm cycle and excluding all the data of the previous cool cycle… Indeed, this is a bit short to draw conclusions from.

Even if they describe their paper as a breakthrough and they seem to be very sure about human attribution, the conclusion doesn’t seem to be clearcut in favor of human attribution (my bold):

[…]If the observed increasing number of summer months with high-amplitude wave numbers m=6, 7, and 8 indeed is the result of ongoing global warming, then we have described a possible dynamical mechanism for how global warming might contribute to future extreme summer events.[…]

While the described processes seem plausible, they don’t seem to prove human attribution and again produced AFTER the facts. In a way, I don’t have a problem with the theory, nor with the adjusting. A theory can be adjusted when the observations don’t fit the theory anymore. But this is different. Over time, the original idea morphed into something completely different. And yes, also this time they found a nice explanation, but it is slowly changing the theory into something different in order to be able to adjust the theory. It also became something non-falsifiable. There is no condition, no weather event that could falsify the theory.

But there seems to be at least one other theory that predicted these new observations in advance. Since I got interested about climate, I learned that climate comes in cycles. It was not uncommon to read that a cooling period was ahead. This because of several cycles that would go negative together, but also a sun that went to sleep and volcanic activity as a possible amplifier. At that time it seemed a bit ridiculous to hear about, but after a while it made sense. In that light the current stagnation/cooling was no real surprise to me. This of course doesn’t mean it is necessarily true, but it gives an indication that it probably is well founded. I have more confidence in a theory that predicted the observations all along, than in a theory that has to be adjusted every time observations change.

Why are we so hooked to a theory that seems to be wrong every time the observation changes? And yet we seem to stay confident in it…

The science is clear…


Reading the dossier that the Flemish Green party prepared as a proof that our government is wrong about its climate goals: “Climate disruption: long winter, bad spring – The link between climate disruption, long winters and more precipitation” was an educational experience. Already the title caught my attention. Longer winters, that is a new thing. Previous, shorter winters were predicted. Also wet winters (more rain, less snow) and dry summers. According to the dossier the prediction of more precipitation in winter still stands, but there are seemingly no changes in precipitation in other seasons (although a small increase in summer precipitation since the 1970s…).

There are three sections in the dossier: first there were the statements of scientists and a weatherman, second part is about precipitation and last part about climate politics in Belgium and more specifically Flanders. I will first look into the first statement.

It is from an article from De Morgen (Flemish newspaper) of March 26, 2013 in which Jean-Pascal Van Ypersele (vice president IPCC) explained that by changes in the jet stream there are more North-South winds than West-East winds. This means more extreme temperatures (if there is a North-South wind → colder, if there is a West-East wind → warmer). It seems plausible. In fact, the explained phenomenon sounds rather familiar to me.

First, it is a real phenomenon, but no mention of its name: the “Arctic Oscillation” (AO). Yes, OSCILLATION. As in possibly having phase shifts. Indeed, the AO index went in a negative trend a couple years ago (but also other oscillations went negative), so it would be no surprise that the temperatures went down.

This is how Wikipedia explains the cooling/warming influence of the Arctic Oscillation:

The degree to which Arctic air penetrates into middle latitudes is related to the AO index, which is defined by surface atmospheric pressure patterns. When the AO index is positive, surface pressure is low in the polar region. This helps the middle latitude jet stream to blow strongly and consistently from west to east, thus keeping cold Arctic air locked in the polar region. When the AO index is negative, there tends to be high pressure in the polar region, weaker zonal winds, and greater movement of frigid polar air into middle latitudes.

Second, it reminded me of the ice age scare of the 1970s, in which the same phenomenon (upper atmospheric wind patterns that favors North-South circulation i.s.o. West-East circulation) was brought in to explain a return to an ice age (this scare was probably a Northern Hemisphere thing, probably more about this in a later post).

The statement he starts early with is: “the science is rather clear on this”. When I hear such a statement, my BS meter is going into overdrive. I heard this many times before and afterwards it was wrong anyway. Sure, the science is clear, but what exactly is the science clear about? Is it about the phenomenon (which I think is real) or about human attribution (which I think will be hard to proof)? When it is the last thing, he could have a point there (he tries to connect the vertical winds to human emissions, via the melting icecap), but I think it is the first thing he means. Not all scientists are sure about the attribution. They consider it, ahem, a natural cycle.

A question I ask myself: when in the positive phase the signal is in the same direction as global warming, how to differentiate between the two?

In the end, we really can be comforted that, although in the past something completely different was predicted/projected (by the same people), global warming is still on track and the science is still clear as ever. 😉

All ravens are black, except when they are not


In previous post Snow, a thing of the past I explored the positions of both sides of the debate concerning the connection between snow and global warming. One thing I didn’t touch yet was the skeptics’ remark that “One can not have it both”. There were statements before that snow was a thing of the past because of global warming, but now when snow falls in abundance, there is the statement this is also because of global warming. If this is the case, it can not be proven right nor wrong.

By their nature, skeptics are, well… skeptical. They want testable statements that can prove or disprove something. This is rooted in science and is called falsifiability. In the most simplest way it looks like this: a hypothesis (testable statement) must predict at least one observation by which it can be refuted. If the evidence is in line with the prediction, the statement may be right. If the evidence conflicts with the prediction, the statement is wrong.

Maybe a bit theoretical, so an example to make it clear. Let’s suppose the statement: “All ravens are black”. It can be made testable by stating that if all ravens are black, this means no raven with another color will exist.

  • If we find a white raven, then the statement “All ravens are black” is clearly wrong: it is falsified (proven to be false)
  • If we see only black ravens, then the statement might be right. “Might” because there is always the possibility that we just didn’t find the ones with another color. They could exist, even if we didn’t find them (yet).

By the way, white ravens do exist (although they are rare).

This is a very simple example and it should be nice if this was also applicable to global warming. The reality is not always that simple. Predicting something is hard, especially about the future. Especially about a complex thing like the climate. So statements about global warming will be stated in a less clear manner. Something like: “it will be more likely”, “it might” or “it is unlikely”. These are all stated as a probability.

One problem: statements based on probability are not falsifiable by default. This is not difficult to understand: suppose one has the statement It is very likely that the frequency of heavy precipitation events will increase. Suppose we define very likely as more than 90% chance. What happens when we test the precipitation in certain places over a certain time?

  • If we find an increase in heavy precipitation, the statement might be true.
  • If we find a decrease in heavy precipitation, the statement isn’t necessarily false. There is a possibility of at least 90% of an increase, but this also means a possibility of up to 10% equal or a decrease in heavy precipitation. It might even be possible that the precipitation was measured in a different place where the increase was not observed. Or maybe the time frame wasn’t long enough to be able to see the increase.

In conclusion, even if the outcome is not consistent with the statement, it doesn’t falsify it.

Of course, first the meaning of increase in frequency and heavy precipitation and probably also the time frame have to be defined. If not, the statement is almost meaningless and one could prove about everything.

This seems disturbing. Does this means that many of the global warming statements can’t even be falsified? I was puzzled about this for a long time. Now I think it is not necessarily true. In the real world we realize that falsifiability is important, but not the only thing being taken into consideration.

Suppose a probability statement that eventually fails. As we saw this doesn’t mean the statement is false, but it doesn’t exactly add to the credibility of the statement and those who make it. The higher the probability with which the statement was stated, the more credibility loss. It is not surprising at all to see fading confidence if observations are not in line with what one would expect from the theory.

A non falsifiable statement looks like a horrible thing when trying to prove or disprove something. But look at it from the other side: a probability statement has, well…probability. Snow and heavy precipitation are consistent with the theory of global warming, but they are also consistent with other things. There isn’t necessarily just one theory. By the fact the theory has to be proved by probability statements, there will be at least one competing theory, maybe even more. All with their own probabilities, explanation of previous observations and predictive value.

This post started with the remark “One can not have it both”. Well, can it? Of course not. At least not in the sense of piling up statements so a theory will be confirmed with any observation possible. That would be the same as stating that “All ravens are black, except when they are not”. This doesn’t learn us nothing new, the predictive value of this is exactly zero.

It is easy to come with an explanation after the facts. The real test is how a theory predicts data we haven’t seen yet and also describes previous and current observations best. This doesn’t necessarily means falsification in a strict true|false way as we would expect with the “One can not have it both”-remark. But rather a comparison between competing theories.

Snow, a thing of the past

Solwaster snow

This winter I often heard the claim that blizzards and snowfall don’t disprove global warming, but that excess snowfall was exactly because of global warming. This was nothing new. I heard these claims for the first time in 2010. That time the winter brought a lot of snow and some record breaking snowstorms. The claim was that warm air can hold more water than cold air and is expected to produce more precipitation, which will be snow when it is cold enough. A higher temperature means more moisture, so potentially more extreme snow events.

On the other hand, skeptics were saying that global temperatures are in a standstill for at least a decade and a half. And isn’t snow something that falls when it is cold? They also were puzzled: is there any weather condition that doesn’t prove global warming? One can not have both.

I have no problem with neither of them. Both sides seem plausible. But what is the truth: does global warming really causes more snow? What is the reasoning behind this? If both are possible: when more and when less?

After looking into the issue, I think they are both right. But they don’t talk about the same things, therefor misinterpreting the arguments of the other side.

The two sides

As far as I can understand the arguments: higher temperatures means more moisture in the atmosphere, which results in increased precipitation. Where it is still cold enough, it will fall as snow. Therefor global warming will lead to more snow in colder regions where it is still cold enough to be favorable for snow formation.

This seems logical and I can agree with these principles, but I think there is more to it than just that. For snow to form, much more is needed than just cold and moisture. It is a delicate balance between several conditions that all have to be met. If one of them is not met, precipitation will fall as rain. Only if all those conditions hold in a warming world, it allows for (more) snow.

The skeptics are right that snow is falling where temperatures are low. This is one of the conditions for snow to form. It also seems that global temperatures are flat lining for the last decade and some datasets even longer.

Temp datasets from 1979

Temperature datasets from 1979 (Woods for trees)

This doesn’t necessarily contradicts the AGW theory, but that is a different discussion altogether.

But, wait a moment…

Understanding the relationship between snow and global warming is surely a nice thing, but is this really the issue? Aren’t we forgetting something?

This is not what was predicted or projected in the past. As far as I know, before 2010 we were told about WARM winters with LESS snow and MORE rain. We were warned about the severe impact this could have on agriculture and on tourism. We were told to act immediately on this. By the way, this was the reason for me to start investigating this whole issue. The discrepancy between what was said and what happened in the real world, made me more eager to find out why.

A statement that is repeated often: “Snow is consistent with global warming”. It is more important what it doesn’t say than what it does say. It doesn’t mean there is proof that more snow will fall because of global warming. It only means that snow is possible, or at least not impossible, in a warming world. Consistency is only a weak criterion. Yes, snow is consistent with a warming world, but it is also consistent with a cooling world, local cooling, local warming and who knows how many other theories and conditions. At such it doesn’t really explain much, but could be very misleading to the public. They could get the impression this is yet another settled part of the science, while it is just one of the many possibilities.

I also have a problem with the way this was and still is presented to the public. It is presented as if it was very clear to the scientists all along. We hear stuff like “We weren’t surprised” or “The science is clear”. As if they knew it all before. The snow/global warming connection is a nice explanation and could be convincing. Pity it was only produced after the facts.

What did I learn?

My first reaction was to start checking the statement. Is there more snow in a warming world or not? The physics seems clear, but unless I want to dive into the topic myself, I have to leave it to those who know more about it.

What I completely seem to have ignored was that the statement about the connection between snow/global warming was only made after the facts and therefor showed no skill. It was also in contrast with earlier statements. But the message is carefully crafted so global warming is back in the attention and is reaffirmed as still going. Reporting a standstill in the increase of at least a decade would be more in line with the available data. How can one attribute the snowfall of the last two or three years to a global temperature increase that just wasn’t there for at least the last decade?

Although strong statements are made in the media, you only have to look a few years back to notice there is much less certainty than what was claimed. Looking back for a couple decades and you will find some statements are exactly the opposite, but wrapped in the same package. But that is yet another story.