Not these ones, though. They're certainly going to reduce emissions in the local area, but their solution inherently cannot scale up. Their planes are tiny, and their flights are super short. It's basically as different from regular commercial flights as you can get, while still working with airplanes.
But not a "major" impact. The vastly bigger problem where Harbour Air operates is "real" flights (because it's the YVR area) and cargo shipping (because it's also the port of Vancouver).
And for this area specifically, it'd be nice if we stopped having a giant, uncovered piles of sulphur pellets, full of sulphur powder from being dumped in piles, literally getting dispersed every second there's even the faintest amount of wind. Which, given that it's the pacific north west, is "every second of every day".
Unfortunately we don't really have the battery technology for this to work for long range flights, like the commercial flights that make up the bulk of air traffic carbon emissions.
I expect the best near-term solution is just to find a way to synthesize jet fuel (or something that works equivalently) on a large scale from something other than fossil fuels. I don't know what the state-of-the-art is in synthetic fuels.
Another option would be to find a way to transfer electricity to a moving aircraft so it could recharge in the air, but I have difficulty imagining how that could be made to work (microwaves? high-power lasers and solar panels? wires held aloft by zeppelins?), especially within the constraints of modern technology.