11/18/2024climate, climate change, disaster management

Consistent climate protection needed

The climate is already significantly warmer than in pre-industrial times, in Austria by 2.9 degrees, in Switzerland by 2.8 degrees. In Germany, the past ten years have been 2.3 degrees warmer than when measurements began.

2024 also confirms the trend towards an increasingly warmer climate and is even on course for a record in Austria and Germany. Analyses by GeoSphere Austria, the German Weather Service and MeteoSwiss show that the warming has already had significant negative effects, such as a massive increase in heat stress, less snow at low altitudes, more heavy rainfall events and a higher risk of droughts.

With consistent climate protection, further negative effects could be significantly mitigated in the coming decades. Without climate protection, a further acceleration of the current development is to be expected. On the occasion of the UN Climate Change Conference COP-29 in Baku (Azerbaijan), GeoSphere Austria, the German Weather Service and MeteoSwiss summarise some key topics on the past and future of the climate in Austria, Germany and Switzerland:

The ten warmest years in recorded history were in the recent past

Since pre-industrial times (comparison with the period 1881-1910), the average annual temperature in Austria has risen by 2.9 degrees, in Switzerland by 2.8 degrees, and in Germany the past ten years have also been 2.3 degrees warmer than in the period 1881-1910.

Since 2000, almost all years in Austria, Germany and Switzerland have been among the warmest years in recorded history. 2024 also confirms the trend towards an increasingly warmer climate and will once again be one of the warmest years in recorded history in Austria, Germany and Switzerland.

Warming is already having a clear impact

The warming measured in recent decades is already having an impact on many areas that affect our natural livelihoods. Here are a few examples:

Heat stress is increasing massively

There is less and less snow at low altitudes

Due to the warming, precipitation falls more often as rain instead of snow at low altitudes and fallen snow melts again more quickly. At high altitudes (above approx. 2000 metres above sea level), the amount of precipitation in winter has a greater influence on the snow conditions than the temperature, as it is usually cold enough for snowfall here despite global warming.

In Austria, the number of days with snow cover in Vienna, Innsbruck and Graz, for example, has decreased by around 30 per cent over the past 90 years.

On the Swiss Plateau, the number of days with snow cover has decreased by between 25 and 35 per cent over the past 90 years, with the main drop occurring at the end of the 1980s with the strong winter warming. Shortly after 2000, there were temporarily snowier winters on the Swiss Plateau. In recent years, however, a pronounced lack of snow has been observed again.

In Germany, the average number of snow cover days has also decreased. In Munich, for example, there are now on average around nine fewer days with snow than at the beginning of the 20th century, while in Berlin there are ten fewer days than the average for the period 1951-1980. However, this trend is overlaid by a high degree of natural variability. In the recent past, for example, there have repeatedly been winters with many days of closed snow cover across the board, such as in the winters of 2009/10 and 2012/13.

Heavy rainfall events are already becoming more frequent and more intense in many regions

The warmer the air, the more moisture it can absorb and the more rain can fall. This also increases the likelihood of localised flooding and mudslides.

In Austria, an analysis based on observation data shows that the number of days with heavy precipitation has increased in summer and autumn, while days with little precipitation are becoming rarer. Specifically, for example, the number of days with extreme rainfall has increased by 30 percent in summer and 40 percent in autumn since the 1960s.

In Switzerland, there has been a significant increase in daily and multi-day heavy precipitation over the past 120 years until the early 1980s and a decline thereafter. Long-term trends are predominantly positive with +11 per cent in the intensity and +25 per cent in the frequency of daily heavy precipitation. Short-term events were also analysed for the period 1981-2023, with an increase in precipitation intensity in summer but no change in frequency. These trends are influenced by climate change and atmospheric dynamics.

In Germany, the changes in heavy precipitation are complex and strongly regionally characterised, which is why no clear trend can be identified across Germany. However, both the 12-month episodes from July 2023 to June 2024 and October 2023 to September 2024 were the wettest 12-month periods in Germany since records began. Embedded continuous rainfall events have led to large-scale flooding in various parts of Germany.

Durch die Erwärmung steigt die Wahrscheinlichkeit für Dürreperioden

In addition to precipitation, temperature also plays a major role in the development of periods of drought. The warmer it is, the more moisture evaporates from the soil. In addition, higher temperatures extend the vegetation period and thus the time in which plants draw water from the soil.

Studies for Germany show a decrease in soil moisture, particularly during the vegetation period in spring and summer.

In Austria, the climatic water balance (taking into account precipitation and evaporation) has shifted towards drier conditions in the summer months, particularly in the east and north of the country.

In Switzerland, for example, measurements in Bern show that the past twelve years have all been drier than the long-term average during the vegetation period. The persistent and often pronounced summer drought of recent years is apparently a typical consequence of the increasingly hotter and more evaporation-intensive summers in Switzerland.

Only consistent climate protection can slow down negative developments

These trends are very likely to continue in the coming decades. The extent of the changes remains to be seen. In the event of far-reaching measures to reduce greenhouse gas emissions, as envisaged in the 2015 Paris Agreement, further warming could be significantly mitigated. The further effects would then also be significantly lower. Every tenth of a degree of avoided warming counts to minimise the negative consequences.

Current development predicted several decades ago

The effects of global warming that have already been measured and observed were in principle predicted by climate models several decades ago.

The currently observed warming, particularly in Austria, but also in Germany and Switzerland, is even at the upper end of the calculations made by the climate models (see figures). According to current knowledge, it is the necessary air pollution control measures since the 1980s (fewer man-made aerosols) and a decrease in cloud cover since the 2000s that are additionally intensifying the warming in Europe. These processes have not yet been sufficiently taken into account in some climate models.

Two possible developments for the coming decades

Independently of this, two possible developments for the coming decades can be derived from the model simulations:

If global greenhouse gas emissions continue unabated (scenario RCP 8.5), the climate in Austria, Germany and Switzerland will warm by a further 1.5 degrees to 4.5 degrees by 2100 and will then be 4.0 to 7.5 degrees above pre-industrial levels. This would have massive consequences, including a further increase in heat stress, even less snow at low altitudes and more and more intense heavy rainfall events.
With consistent global climate protection (compliance with the Paris climate targets, scenario RCP 2.6), warming and the associated effects could stabilise at just above the current level.

For example, in Austria, the current extreme value of 40 heat days per year at low altitudes (days with a maximum temperature of at least 30 degrees, also known as hot days) would be the norm by 2100. The records would then be in the currently unimaginable range of 60 to 100 hot days per year.

In Germany, an average of around seven hot days per year are currently recorded; at the end of the 21st century, assuming continued unchecked greenhouse gas emissions, the average number of hot days in Germany would increase by up to 28 days, with over 40 hot days per year expected in large parts of Germany.

At the Zurich measuring site in Switzerland, the average number of heat days without climate protection is expected to rise from the current eight to nine to 27 to 57 heat days per year by the end of the century.

The contribution of all countries counts in climate protection

In order to limit the negative effects of global warming, man-made greenhouse gas emissions must be reduced to net zero wherever possible, which means that all man-made greenhouse gas emissions must be removed from the atmosphere through reduction measures.

As the total global amount of these emissions defines the warming and therefore the severity of the consequences, all countries, including Germany, Austria and Switzerland, have a responsibility to contribute to reducing emissions.

Austria under climate change. The bars show the deviation in temperature in previous years compared to the pre-industrial climate average in the period 1881-1910 (red = warmer, blue = colder). The red area shows the range of climate projections for the coming decades assuming unchecked global greenhouse gas emissions, the blue area assumes consistent global climate protection (compliance with the Paris climate targets).

Germany under climate change. The bars show the deviation in temperature in previous years compared to the pre-industrial climate average in the period 1881-1910 (red = warmer, blue = colder). The red area shows the range of climate projections for the coming decades assuming unchecked global greenhouse gas emissions, the blue area assumes consistent global climate protection (compliance with the Paris climate targets).

Switzerland under climate change. The bars show the deviation in temperature in previous years compared to the pre-industrial climate average in the period 1881-1910 (red = warmer, blue = colder). The red area shows the range of climate projections for the coming decades assuming unchecked global greenhouse gas emissions, while the blue area shows the range assuming consistent global climate protection (compliance with the Paris climate targets).

Translated with DeepL.com (free version)

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