IELTS Writing task 1: sea level

Good evening Carola! This is a great writing sample with decent structure and only tiny mistakes. I was incredibly impressed with how many conjunctions and different sentence structures you used! Awesome work!:

However, as for the span of time between 1860 and 2000, it has been measured that the increase was more significant; sea level reached 20 mm in 2000. Nonetheless, the most impressive characteristic of this graph is related to the future, as a matter of fact it is predicted that in just 100 years sea level will irise to 500 mm. Finally, we can conclude that while in the past sea level was rising quite steadily, in the future its increase will probably be very rapid and abrupt.

I have just a couple of comments/suggestions:

Increase: While "go up" is technically correct, you'll want to make your paragraphs sound more sophisticated by using increase (rise)/decrease(decline) instead of up/down 

Whereas: Using whereas at the beginning of the sentence sounds a little un-natural. It's mainly to show contrast in the middle of sentences, i.e. (Sam is 6 years old whereas Tom is only 3). If you have to split the sentence into two sentences, try using however (Sam is 6 years old. However, Tom is only 3). 

As a matter of fact: As a matter of fact is mainly for use at the beginning of the sentence. It's more like an affirmation: 

"Do you have gum?"

"As a matter of fact, I do!"

Has been: Has been indicates a continuous action which is still taking place, or only recently stopped. 

"Roger Federer has been winning Wimbledon since 2015."

However, if the action has stopped or was momentary, you use was 

"Roger Federer was the champion in 2015."

The semi-colon (;): If you are joining two different sentences (instead of the colon) i.e, (Sam is 6 years old; Tom is only 3). 

Very: I would avoid using very to make your piece sound more sophisticated.