Humans have caused 1.5 °C of long-term global warming according to new estimates

Does the IPCC account for asphalt expansion (added heat) around all the airport sensors as cities expand? What data source do they use to track and compensate for this growth?

>asphalt expansion (added heat) around all the airport sensors as cities expand

Why would this be relevant? The airport itself represents quite a bit of land area (thus, a significant distance to any heat sources that could be considered "the rest of the city"), and much of that was already paved the entire time.

Asphalt holds heat from the sun. Cities produce heat plumes that grow as the area of asphalt grows. Even without wind the plumes will expand to the airport and the temperature will increase. Cities grow in circumference expanding the overall area and temperature of the heat. This also increases the heat at night as the asphalt slowly releases the heat after dusk.

What I'm asking is, what mechanisms allow such expansion to occur over distances that would be relevant to the measurement? The expanding edge of an urbanized area might be many kilometres away.

Yes. Some data-source that already takes that into account, that issue has been already solved.

Most uncertainty in temperature does not come from measured temperature (weather stations) but from temperature estimations from indirect sources. In other words, last 50 years data is pretty much all good.