Hamburg Climate Futures Outlook 2021
Hamburg Climate Futures Outlook 2021
Photo: UHH/CLICCS
In the Hamburg Climate Futures Outlook, CLICCS researchers make the first systematic attempt to assess which climate futures are plausible, by synthesizing research from disciplines as varied as sociology, macroeconomics and earth system science. In this way, CLICCS helps to narrow down the multitude of future scenarios to inform policy and individual decisions.
Key FindingsClimate Protection: Deep Decarbonization by 2050 Currently not Plausible
CLICSS publishes a new, essential study on climate futures. The study represents the first systematic attempt to investigate whether a climate future with net-zero carbon emissions is not only possible but also plausible. The authors examine plausibility from a technical-economic perspective, but also with regard to the societal changes necessary for such a future. They conclude that deep decarbonization by 2050 is currently not plausible – the current efforts to bring about societal transformation need to be far more ambitious.
More information
Figures
The material below is the property of CLICCS/University of Hamburg and is protected by intellectual property laws. Please respect the copyright.
Plausibility of net global CO2 emissions by 2050. Download figure as jpeg file.
Figure 1: The speedometer shows the wide range of possible emissions in the year 2050 as described in existing emissions scenarios. Emissions could reach net-zero by 2050 (deep decarbonization) or could increase up to a doubling of current emissions (very high emissions). Approximate emissions in 2020 are indicated by the speedometer needle. Here we find a reduced range of plausible emissions scenarios, supported by a techno-economic plausibility assessment (Chapter 3) and a social plausibility assessment (Chapter 5), indicated by the shaded bands. Increasing emissions are not yet considered in the social plausibility assessment (gray band).
Components of the Social Plausibility Assessment Framework. Download figure as jpeg file.
Figure 2: The figure shows the chosen climate future scenario, deep decarbonization (right), and the selected key social drivers of deep decarbonization (left; see Chapters 5 and 8 for a description and analysis of the drivers). The assessment of the driver dynamic (center), their enabling and constraining conditions, and the potential global opportunity structure leads to a conjecture about the plausibility of the future scenario (Section 5.3).
The global opportunity structure. Download figure as jpeg file.
Figure 3: Social drivers (left) provide resources that become more material as they move from left to right in the figure. If the resources become visible to societal agents on a global level (center), these agents can use and combine them in material ways, which can influence driver-specific environments and therefore the enabling and constraining conditions of other drivers (right).
Projected 21st-century global surface warming. Download figure as jpeg file.
Figure 4: The 90% uncertainty ranges are indicated by shading around the central estimates (lines). Observed global surface warming is shown by the black line (Morice et al., 2021). The warming is simulated relative to the recent reference period 1995–2014 (left vertical axis). To convert to warming relative to the pre-industrial period, we note that the period 1995–2014 was observed to be warmer than the period 1850–1900 by 0.87°C (Morice et al., 2021; right vertical axis).
Detecting the effects of emissions reductions. Download figure as jpeg file.
Figure 5: Top figure shows atmospheric CO2 concentrations for two emissions scenarios, RCP2.6 and RCP4.5. Bottom figure shows an ensemble of 100 global surface warming responses to each concentration pathway (generated by the MPI-ESM Grand Ensemble; Maher et al., 2019). The ensemble mean warming is shown by the thick lines, individual simulations by thin lines. The bars describe the range of warming generated by each ensemble for the years 2040, 2060 and 2080.
Amplified regional internal variability. Download figure as jpeg file.
Figure 6: Simulations with the MPI Grand Ensemble are grouped according to when the global and decadal average surface temperature shows no warming (pre-industrial, pre-ind), or when it is warmer than the pre-industrial by either 1.5°C (blue) or 2°C (red). For each such decade, the figure shows how often the European annual summer temperature increase attains a certain value. The summer values are grouped in intervals of 0.075°C. Adapted from Suarez-Gutierrez et al. (2018).