The observation instruments measure reflected sunlight, heat emitted, cloud structure, sea level and many other variables.Their strength is repetition: the same calibrated view is repeated for months and years.
A satellite image is not automatically a climate archive: researchers correct for sensor drift, atmosphere, angle of view and gaps before comparing observations over time.
The resulting datasets complement weather stations, ocean buoys and field campaigns and together help to distinguish a brief event from a long-term trend.
References and further reading
