On​ ​the​ ​Great​ ​Barrier​ ​Reef,​ ​how​ ​warm​ ​does​ ​the​ ​water​ ​need​ ​to​ ​be​ ​for​ ​corals​ ​to bleach?​ ​​ ​ b. How​ ​many​ ​weeks​ ​did​ ​the​ ​temperatures​ ​exceed​ ​the​ ​‘bleaching​ ​limit’? c. How​ ​many​ ​degrees​ ​above​ ​the​ ​bleaching​ ​limit​ ​did​ ​the​ ​sea​ ​surface temperature​ ​rise​ ​during​ ​the​ ​week​ ​of​ ​Feb​ ​18th,​ ​2017?​ ​​ ​