Philadelphus in Spring

If a ten-mile-long iceberg breaking away from the Canadian Arctic coast - Ayles Ice Island - hasn't convinced you that global warming is a fact, then how about some evidence closer to home? My garden has a large Philadelphus coronarius shrub that's at least 70 years old. It always used to blossom during Wimbledon fortnight (the last week in June and first week in July). In the last few years I've noticed it flowering two weeks early. This year, it's in blossom now: more than one month early!