By Frank Bosse
An outcry went through the media: this is how expensive the “climate crisis” will be for Germany alone. All major media houses reported uncritically, with one exception. An extremely critical article appeared in “Welt”. The author Axel Bojanowski criticized above all that the basis for the current report on costs, a comprehensive report by the Federal Environment Agency (UBA) on the expected climate conditions for 2050 and 2100 from 2021, assumed far too high loads.
We therefore took a closer look at it. In its projections, the IPCC works with different scenarios with regard to the impact of man-made drives, roughly distinguishing between quite small sizes (1.9 or 2.6 W/m² additional drive by 2100) and very strong (7.0 or 8.5 W/m²). In between are medium loads (4.5W/m²).
Which are likely? For some years now, a dispute has been raging among scientists as to whether 8.5 W/m² should be classified as realistic at all, whether it could be a possible one that describes a “business as usual” in the use of fossil fuels. Already at the beginning of 2020, a comment appeared in “Nature”, which already described this in the headline as misleading. In the serious literature, there were then efforts to evaluate the scenarios soberly. Pielke et al (2022) concluded that the high values are very unlikely. The IPCC itself largely confirmed this and stated in the last assessment report:
“High-end scenarios (like RCP-8.5) can be very useful to explore high-end risks of climate change but are not typical “business-as-usual”.
So much for the current findings of science. The report (linked above), which shows the status of UBA on behalf of the Federal Ministry for Economic Affairs and Climate Protection (responsible Minister Robert Habeck), took a completely different approach. Only the scenario “RCP 8.5” was used! Even the “optimistic cases” only reflect this scenario, then at the lower end of his expectations.
How do you justify this? With EINER literature source from 2020, which attempted to draw conclusions from the emission data until 2019 about what will come until 2100. The limits of extrapolation are made clear elsewhere in the report:
“… because the different scenarios do not differ significantly at this stage.” (p.23).
The goal is also clearly formulated:
“RCP8.5 for KWRA 2021 was selected for precautionary reasons in order to ensure sufficient dimensioning of possible adaptation measures.” (p.23).
So it was not a question of making realistic projections for the effects of climate change in Germany, they simply took the “highest impact” scenario as what awaits us with “business as usual”. The implications are extraordinarily far-reaching.
Tables 1 and 2 give figures for the increase in average air temperatures, for case 2100 it is up to almost 5°C above the level of 1971… 2000. This is indeed the result of the CMIP-5 model mean under the scenario RCP8.5 for the territory of Germany. The RCP4.5 scenario, which is described in the literature as far more likely, suggests values of 2.5°C, it should even be only 2°C compared to 1971… 2000, recent findings on the sensitivity of the climate system to CO2 increases are taken into account. Table 2, on the other hand, gives 3.1°C as the lowest value to be feared.
The entire UBA study is thus misleading, to return to the title of Hausfather / Peters (2020). The 900 billion that are to be incurred as climate follow-up costs are plucked out of thin air. The fact that something like this will be sold as science in Germany by the Federal Environment Agency in 2023 is shameful.