GMAT Sentence Correction (SC) | Re: According to scientists at the University of Alaska, while

I wouldn’t think B is wrong.
Let’s go case by case
(A)the surface temperature in Alaska, Siberia, and northwestern Canada has increased in the previous thirty years by about five degrees --- ‘Over the previous’ means that the thirty years do not include the present. Then we cannot justify the use of present perfect ‘has increased ’ wrong