There once was this US senator who brought a snowball to the parliament to proof climate  change is not as bad as we wanted him to believe.

A small act, you could even call it a joke, yet it pops up in my mind every time our world is covered in snow and ice. Yes, it is cold, it can even be extremely cold, it can even snow in Spain and the Sahara. But that does not mean climate change is less real.

Being blinded by a bit of snow is a common misconception. The senator with the snowball could do with a look at the video of the man who walks his dog, showing the difference between trend and variation. The happy dog hops around, going left, going right, going straight, sniffing and looking. His trajectory highly unpredictable. Yet, slowly and steadily, he is going towards the upper right corner of the panel. Even though every next step of our little buddy could surprise us, we still now he is going to end up there. And that is because of the owner, the man on a line, the trend line. The dog symbolises the weather, unpredictable in its every move. The owner is the climate, slowly and steadily warming.

We know this is happening. We do not need the absence of snowballs to proof it. You can see it in our longterm data, like this beautiful, yet shocking, timelapse of the worlds temperature from 1880 till now:

More on this one on nasa.gov.

So we should not look at the variation, but at the trend. True. But what if our steady-walking owner is not going in a straight line? He might make some turns as well? And that brings us to another argument of climate change deniers: if we zoom out far enough – let’s say a few thousand or even million years – our owner has been walking all over the place. He has been higher, he has been lower, he has been everywhere.

True. Our climate has seen some variation in the past. Yet we know now that our owner now is climbing an increasingly steep slope. We know that such steep slopes have been extremely disruptive for biodiversity in the past. And we also know that it is our emission of greenhouse gasses that is chasing our guy uphill. Clearly he has been everywhere, but rarely he moves so rapidly, and when he did, it was often catastrophic for live on earth.

Earlier this week I went to a lecture from Jens-Christian Svenning, a scientist from Danmark. He studies longterm effects of climate on biodiversity, and his story is fascinating. He showed that our world is still catching up to climate events from the past, some of them even millions of years ago. The fact that we do not have some species in the Scandinavian mountains that could be there based on where they live in the Alps, or that we do have tons of palm species in the Americas yet relatively few in Africa, it is the result from longterm changes in the climate. This shows how long-lasting the effects of a change in the climate can be. Climate change effects in the past have been big, and their legacy is still felt in the present. Then what to expect from this sudden, massive change in climate that is currently upon us? How far will these effects go? But what this shows most clearly, is that species adjust their distribution to changes in the climate, yet that they are limited in how far they can go.

So yes, the owner is the trend, but that does not mean that the dog does not matter! On the contrary. Extreme weather events, from one year to the next, can have a massive influence on our world. One big frost or drought is sometimes enough to disrupt a whole ecosystem. Indeed, plants and animals do not experience the trend as it is, no, they experience the weather from day to day, often even with small-scale variations over distances of a few meters (or less!).

So, why bother with the owner as it is the dog that is felt in reality? To grasp that, you best check the first video again. Our dog is following the same route as his owner, albeit not directly. We know that the owner/trend will end up at the top right (if nothing changes his path), even when the dog sometimes heads down. Moreover, yet not shown in our little video, we know now that on his way to the top, the dog is getting more and more excited. Climate change is resulting in more extreme weather events, the dog starts to care less about his owner: more ups, more downs, more jumping all around. As it is these ups and downs, these extremes, that are felt by those living on our planet, this obviously creates additional strains on the living world.

So where does this leave us? The smallest scale matters. Yet if the trend is moving upwards, the small scale will follow. More extremes might force the world to adjust rapidly. Yet we know from looking at the past that there is a limit to the adaptability of species. Cross that line, and they are inevitably lost. It leaves us with the conclusion that we should take our climate seriously, and not just throw snowballs and move on.

Want to know more? Check out skepticalscience.com for more common misconceptions about climate change.