Lighting candles earlier in Israel?

I was looking something up on Hebcal and noticed they said that Shabbat candles are lit 40 min before sunset in Jerusalem and 30 minutes before sunset in Haifa (as opposed to 18 minutes before in most places, which is my minhag as well). Why is this? I tried googling and all I found was an oblique reference to the halachic hour (which is apparently 40 min in Jerusalem at some times of year). Why would Jerusalem (and Haifa?) be lighting Shabbos candles one halachic hour before sunset, but not the rest of the world? Why always 40 minutes, even though the halachic hour is different at different times of year?

inB4 someone tells me it’s foolish to ask halachic questions so close to Shabbat – I’m posting this at 9:45am local time, on a Friday. I think it’s early enough to get some responses and if not, I’ll try again after Shabbat.