Sure! Here are the rewritten sentences:

1. Nelson used to go climbing more often than now. → Now Nelson goes climbing less often.
2. A teacher doesn’t need as many calories as a farmer. → A farmer needs more calories than a teacher.
3. Johnson likes cycling better than going jogging. → Johnson prefers cycling to jogging.
4. It’s not necessary to bring your warm clothes. → There’s no need to bring your warm clothes.
5. She ordered tomato ketchup; she didn’t order salad. → Instead, she ordered tomato ketchup and not salad.
6. How long have you practiced karate with Ted? → When did you start practicing karate with Ted?
7. Colin speaks Spanish more fluently than Graham. → Graham doesn’t speak Spanish as fluently as Colin.
8. You can’t get up early tomorrow if you stay up late. → Unless you go to bed early, you can’t get up early tomorrow.