When you read articles in English, pay attention to these two words: "but" and "and."

 You may notice these two words occasionally are used at the beginning of a sentence, BUT good scientific writing should avoid starting a sentence with either of these two words.

But: When you use this word at the beginning of a sentence, try to change it in the following ways:

Original writing: We carried out many numerical experiments using the new mixing scheme. But, the improvement on climate prediction was limited.

Take 1: We carried out ....; however, the improvement ...

Take 2: We carried out ... The improvement on climate prediction, however, was limited.

And: You should always be able to simply drop this word, if you have it at the beginning of a sentence.  If not, send your writing to me and I will revise it for you or revise this Blog.