The way I see it, carefully choosing a job doesn't matter much (compared to other things you can do) for helping avoid the ecosphere catastrophe as an individual.
Most jobs are the end result of consumers (and also institutions like the state or other companies) demanding whatever products and services they deem necessary. Companies then implement processes to produce these things and then issue job offers accordingly and employ personnel.
If some job vacancy provides enough salary, it will very likely be filled. By you or someone else. By choosing to not do a certain job, you don't influence the demand side for it (which comes from consumers' demand) and if the demand is high, in principle the salary will generally just increase until someone else is willing to do the job.
If you want to gently yet effectively change and shape the whole supply chain and reduce emissions, you can choose to be very conscious of your individual demands that you feed into the worldwide production system.
If you simply buy less unnecessary stuff (right now the best thing you can do) or buy used stuff or buy sustainable stuff ... and if billions of people do the same, we will have a totally different landscape of companies within 20 years.
Living daily life as sustainably as possible, is - in our current western environment - a real challenge. Some people find meaning in trying to accomplish that.
IMO there's nothing wrong with working in a job that's not per se sustainable (say oil rig) and at the same time living your daily life in such a way that shapes your little individual slice of the world wide demand for production so that it's sustainable.