Now I'm no climate scientist / expert / enthusiast.
But I prompt a question, is 'net zero' actually achievable?
For example to make batteries that power EV's it is required to emit carbon to manufacture them, please correct me if need be.
This is just an example, same as solar panels - requires carbon to be emitted to manufacture them.
My point is, and this is not 'climate denying', is that the world does not have the technology (yet) to truly emit zero carbon. So to the thread title '100% renewable' is not actually a thing because at a start point emitting carbon is necessary to achieve that panel or battery.
On Friday, the govt. released it's vague modelling to reach '85%' less emissions, how they come to that number I don't know. And the other '15%' will come from future technologies. It's an admission 'we can't do it yet'
I'd argue no one on the planet can, the tech doesn't exist - yet if you're a govt. or opposition and say 'we can't coz no tech yet' you're a pariah.
I am a person with no technical background in this, but I take a huge interest and read a lot.
I completely agree with you that it is not doable with current technology. We can't make steel or aluminium, we can't have the electricity storage to see us thru periods of low wind and sun, there is no answer for fueling of shipping and planes. While some level of 'negative emissions' may occur thru direct air capture, planting trees or soil sequestration (if that's the right term) I can't see this being close to sufficient to cover all the things we can't address.
As well as the 15% you mention of future technologies (the unknown unknowns), there is another significant percentage of known unknowns such as carbon capture and storage and hydrogen that have to be made to work at scale and financial viability.
I also think there are a myriad of reasons outside of pure technology at a world level. There is a large study performed by Princeton University called Net Zero America which identifies the actions the US needs to take. If I remember correctly, the first thing that needs to be done is double the electricity transmission capacity by 2030 and then add that much again by 2040 (final result of tripling). If you just think about logistical issues like finding the land and going thru planning permission processes it is quite mind boggling. They would have to implement wind and solar at a huge rate year in year out until 2050. (And by the time they get there they will be replacing everything they have put in place in the last 30 years as onshore wind has a life of 20-25 years, solar 30 years, offshore wind not really known but maybe less than 20 years.
Another issue is materials. As a rule of thumb wind and solar require 10 times as much material as fossil fuel power stations etc. They require a lot of specialist minerals (lithium, cobalt, copper etc etc) and the world is just not doing the mining (and exploration etc etc) to cover the future needs. There is a report on this by the International Energy Agency and a report from a British perspective from the British Natural History museum.
Processing, smelting, manufacturing and construction of all this material is never considered.
The scope of work of all this stuff is just mind boggling and it is hard to see how it can possibly occur, without a significant rethink (or even with a significant rethink).
None of this means we should do nothing, and even though our emissions are low on a global level, if we push ahead on things like hydrogen we could have a significant world effect by inventing and proving stuff.
One other thing. My understanding of current thinking of most energy engineers (eg the guy that led the Net Zero America study) is that you need base load electricity, thinking you can go ahead with wind, solar and batteries just isn't going to get financially viable.
One more thing. I worry about the concept of electrifying everything - electric cars and no gas heating, hot water, cooking. It may be not too much of an issue in Australia with its largely warm climate, but in North America and northern Europe a major snow storm could knock out electricity supply for days and people would have no heating, hot water or cooking and quite limited ability to use a car.
I think I have finished.