A photographer shoots a landscape with a fixed-focus lens. The scene changes, but the focus stays the same. It's the same with climate norms: they are calculated as a 30-year average, yet the climate is moving, and the average lags behind.
Scientists have built a new tool: a filter that adapts itself to changes. It looks at the trend and seasonal cycles, then decides how much to trust them. It's like an autofocus lens that tracks a moving subject.
They tested it on ocean temperature: the old and new methods give almost identical results. But for wind speed, the old method errs by up to 2 meters per second. The new filter reduces the error rate from 55% to 3.5%. Now anomalies from the norm reflect real changes, not a flaw in the measuring stick.
The 30-year rule for climate normals arose not from statistics but from practice: when the recommendation was adopted, meteorologists had only 30 years of reliable data at their disposal. Since then, that number has become the standard, even though the climate can change noticeably over such a period.