Given the current warming climate, many of us have wondered if snow around Christmas time is slowly becoming a thing of the past. We asked Alex Vermeulen, Director of the ICOS Carbon Portal at Lund University, what Europeans can expect going forward. Only one thing seems certain: the weather will change in unpredictable ways, with more extreme weather likely.
Around what time will Europeans experience their last white Christmas? Is this a question that is possible to approach with precision?
That is hard to say. There will be white Christmases left for some Europeans for centuries to come, but it will happen for less and less people.
Gulf stream collapse would make certain regions of Northwestern Europe colder in the winter and wetter in the summer, so that would increase the probability of white Christmases in those regions considerably.
Obviously, this is not anything to look forward to, as the increase in occurrence of white Christmases is not worth the other problems that would go together with such a trigger point, like mass starvation both in warmer parts of the world and even so in the colder parts.
How close are we to a Gulf stream collapse?
There is still a strong academic debate on this issue. The standpoints range from virtually impossible to a 25% risk at mid-century, even under 2-3 degree Celsius warming scenarios - that is, the scenario that is the most likely if we implement all the promised emission reductions.
Some papers claim that we actually do not have enough relevant and good observations to say anything conclusive on signs of a possible collapse of the warm gulf stream in the Northern Atlantic.
This gulf stream is part of a bigger flow structure called AMOC (Atlantic Meridional Overturning Circulation) that carries warm salty surface water north from the tropics. The weakening AMOC tipping point is a remote probability, but under high CO2 emission scenarios it might occur, though still with a low probability, at around 2055 or later.
The word collapse sounds alarming, but the whole process of collapse will take some time, as long as a century or so, if it happens at all.
Will different parts of Europe (or the world for that matter) have different changes to their climate - will some parts experience their first white Christmas?
Yes. The warming will be largest on the higher latitude land surface and the poles, and thus reduce the temperature changes between the equatorial regions and the poles. This will lead to a weakening of the higher atmosphere jet stream, in turn leading to more stagnant weather patterns.
Therefore, we will see different weather patterns than we are used to in the current climate, with more persistent rainy periods (and heavier rain as warmer air can contain more water vapor) or the opposite with longer dry periods in other regions. This obviously comes with greater risks of floods or droughts. It is impossible to say what will happen where and when, but we can expect major changes.
If there are changes to man-made climate change that happen soon, would that make a difference at this point?
Yes, every reduction we make sooner rather than later will help. There are only a few years left, and we should reduce fossil fuel emissions with a staggering 7 percent or more year on year globally, until we are at net-zero.
That will be hard and painful, but that is what you get if you spend 30 years sitting on your hands.
How much uncertainty is there in current climate models, when we try to predict these types of things? Have we fine-tuned them in recent years?
Climate models are constantly fine-tuned with the latest observed climate data. Models have improved over the years but as always, predicting outside the current bandwidth will always carry uncertainties. There are different uncertainties and one of them is internal variability, inherent to the climate system, something that climate models should include - this uncertainty is 1-2 degrees Celsius. If we leave that out, the model predictions for the current climate have an uncertainty of just under 1 degree Celsius.
What other factors could affect weather patterns and the possibility of snow going forward?
Until now, we have been saved by the ocean and land taking up about 50% of the CO2 we emit every year. A warming climate and increasing CO2 levels in the atmosphere and oceans may affect this uptake capacity and reduce it. This will in effect further accelerate warming - and force us to reduce emissions even more. Stronger warming might in the long run induce other tipping points and bad effects on the capacity of the world to support our societies.
