2025-11-07 Switzerland and the climate
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Switzerland is slowly about to find out that you can't buy the climate
with money.

> Commissioned by the Swiss federal government and compiled by
> MeteoSwiss, the new scenarios build on the results of the 2018
> climate scenarios. They confirm and expand on the picture that had
> already emerged regarding climate change in Switzerland. The warming
> in Switzerland until now (2024: 2.9 °C up on pre-industrial levels)
> is above the global average (2024: up 1.3 °C). Aspects of climate
> change are proving more pronounced for Switzerland than the mean
> situation worldwide, partly due to the country's geographical
> location. In an overall global warming scenario of 3 °C, the
> temperature in Switzerland is expected to rise significantly more
> than that, by around 4.9 °C. – Climate change particularly
> pronounced in Switzerland, a press release, by the Federal Office
> of Meteorology and Climatology MeteoSwiss

I bet half the population now thinks that maybe the collapse of the
Atlantic Meridional Overturning Circulation (AMOC) is not such a bad
thing since it'll cool Europe, right? Looking at the National Centre
for Climate Services site, I found the new Scientific Report on the
Climate CH2025 page.

> Finally, it is likely that only extreme changes in external forcing,
> e.g., a slowdown of the Atlantic Meridional Overturning Circulation
> (AMOC) due to fresh water supply in Arctic Seas by enhanced
> precipitation and ice melt (Rousi et al., 2021), could cause drastic
> changes in atmospheric circulation over Europe. For Switzerland,
> scenarios with a slowdown of the AMOC suggest even more amplified
> seasonal variations in precipitation, a drastic increase in
> frequency of blocked weather regimes in summer favouring drought and
> heat, and an increase in cyclone-dominated regimes in winter
> enhancing wetter conditions in the cold season (Rousi et al., 2021).
> – Climate CH2025 Scientific Report, via Climate CH2025

That reference is to a paper from 2021. Hm. I have seen more recent
discussions but this one has a pretty clear summary at the very end.
Taking an older and possible wronger paper just because it's easier to
understand feels like the wrong approach to me but what can I do.

> We found significant differences in frequency of occurrence of
> certain patterns in all months. Those differences are robust, and
> they stand out from the uncertainty and the internal variability of
> the model. In February we see a substantial increase (with a
> relative change ranging from 124% to 136%) of zonal circulation
> regimes over the North Atlantic and western Europe, which leads to
> increased precipitation over north-western Europe posing high flood
> risk for these areas. In August the most robust change (ranging from
> 157% to 167%) is that of increased high pressure systems off the
> U.K. coast. This circulation change results in less precipitation
> and longer dry spells over large parts of western and central
> Europe, enhancing drought risk in summer. – Changes in North
> Atlantic Atmospheric Circulation in a Warmer Climate Favor Winter
> Flooding and Summer Drought over Europe

I'm not sure what to make of this:

> Recent simulations using the Community Earth System Model (CESM)
> indicate that a tipping event of the Atlantic Meridional Overturning
> Circulation (AMOC) would cause Europe to cool by several degrees.
> This AMOC tipping event was found under constant pre-industrial
> greenhouse gas forcing, while global warming likely limits this
> AMOC-induced cooling response. Here, we quantify the European
> temperature responses under different AMOC regimes and climate
> change scenarios. A strongly reduced AMOC state and intermediate
> global warming … has a profound cooling effect on Northwestern
> Europe with more intense cold extremes. The largest temperature
> responses are found during the winter months and these responses are
> strongly influenced by the North Atlantic sea-ice extent. – European
> Temperature Extremes Under Different AMOC Scenarios in the Community
> Earth System Model

The conclusion is something like: "We conclude that the (far) future
European temperatures are dependent on both the AMOC strength and the
emission scenario." Hm. 🤔

#Climate #Switzerland