I am agreeing with you.
Yes, they were doing ocean and Earth readings prior to the dates that I mention, but not on a regular wide-scale operation. Taking ship measurements while sailing is not the same as buoy measurements places throughout the ocean.
Building cities around reading stations does not alter the data of thermometers, it alters the temperature of the earth's surface. The thermometers are still giving accurate temperature readings.
Potato, patato... the measure taken may be accurate, but it doesn't reflect the same location and conditions as previous readings, thus altering the validity of the data.
As far as the flip goes. I'm on the side of just a magnetic flip and not a stop of the Earth or a flip of the continents. Either way, there might not be any records of what really happened 10,000 years from now, just like then. ;)
Yes, UV radiation might not be kind to the plants. The increased cloud cover and cold temperatures will be less nice.