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.
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.