Just googled to look at how your cloche is constructed. If you cover the ends and have a warm sunny day, the plants would likely overheat and perhaps die. It would be o.k. to cover the ends if cloudy or very cold, but IMO for carrots that is not likely necessary. Carrots, spinach, radishes, peas, other cool weather crops should do just fine with the ends open. If you try to start warm weather crops early in a cloche, temperature regulation is more important. On a cold night, the ends would need to be closed for things like peppers, tomatoes, squash, beans. Even with that, warm weather crops like warm soil somewhere in the mid sixties or higher, so IMO cloches serve a very marginal purpose for those crops, as it is just best to wait on warm soil for the planting. Early plants can be started in containers and moved back and forth outside to inside, to keep them within the desired temperature range. That is what I do, and just wait on the soil temperature to get warm enough before planting in the ground.