Indeed I checked one of his references where he says that it is cars that are the primary reason that CO2 emissions haven’t reduced in the transport sector. The linked article says that it is airlines (increase of 2%) not cars (decrease of 1%).
“Demand for oil was also largely unchanged in 2018 (-0.3%). Within that total, demand for diesel and petrol both saw annual declines of around 1%, whereas aviation fuel was up 2%.“
Even with a tiny change in relative proportions within transport, road vehicles still use vastly more fuel than aviation in the UK. Without absolute tonnage of emissions, and relative proportion of commercial and private, I can't see a way to invalidate his claim or prefer aviation as culprit. It sounds perfectly reasonable and the least controversial assumption from data available: cars are the big majority of the largest fuel user, though commercial traffic may get low enough mpg to emit disproportionally large amounts.
> George Monbiot is seen as a climate change denier in many circles
Which circles? He has been on the side of science and an outspoken critic of denialists for the last 15 years, both in his columns and other avenues (letters to Nature etc).
Apart from that and in general terms, both sides of a debate thinking you are a lunatic usually doesn't mean you are a visionary - but a lunatic.
Sorry, I can't find the criticism I'm thinking of right now, but I'm sure you'll probably agree that George Monbiot says lots of controversial stuff and has definitely ruffled feathers on both side of the aisle on a number of issues. Almost always I've agreed with George Monbiot.
That being said, you're right that he definitely falls squarely in the anti-climate change denier column.
The side of science? It would help if you defined terms before using them. What is a denialist and who are they? I'm not aware of a single scientist or informed layperson who thinks that human emissions have no effect whatsoever on the climate. The intelligent question is: how much of an effect do they have on the earth's energy balance? Less than x% you're a denialist and greater than x% you're not? Is that how it works? Meanwhile debates about the magnitude of the climate sensitivity roll on with no clear answer.
Doesn't seem especially hyperbolic either.