One of the demands from Extinction rebellion is that the [g]overnment must act now to halt biodiversity loss and reduce greenhouse gas emissions to net zero by 2025. This has been criticised as being so unrealistic as to potentially damage their basic message. Although I think achieving this would be extremely challenging, and may well be virtually impossible, there are a few things to bear in mind. Firstly, these are demands of the UK government, not demands of the entire global community.
Also, if you recall the Paris agreement, it had a central aim to
strengthen the global response to the threat of climate change by keeping a global temperature rise this century well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius.
If you then read the recent IPCC SR15 report it says
[i]n model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030 (40–60% interquartile range), reaching net zero around 2050 (2045–2055 interquartile range). For limiting global warming to below 2°C CO2 emissions are projected to decline by about 25% by 2030 in most pathways (10–30% interquartile range) and reach net zero around 2070 (2065–2080 interquartile range).
In other words, pursuing the aspiration of the Paris agreement would require aiming to cut global emissions in half by about 2030.
If you also think that those countries that are richer, and have contributed more to the problem, should do more, then that might suggest that the UK should aim to do more than halve its emissions by 2030. Alternatively, it should aim to cut its emissions in half before 2030. Maybe not quite net-zero by 2025, but still a substantial reduction in emissions on a very short timescale.
So, you might think the demands of extinction rebellion are ridiculous, but then we did agree to aim for something that would probably require doing something that’s not entirely inconsistent with their demands (very large emission reductions by about 2025). Maybe we shouldn’t have agreed to something that is now regarded as virtually impossible, but it doesn’t seem unreasonable that some are demanding that we at least try.