You guys got me thinkin'
Atmospheric pressure over the last 1000 years has remained relatively stable on a global average, hovering around the standard 1013.25 hectopascals (hPa) or 1 bar at sea level, with significant, short-term variations caused by weather patterns and localized, long-term shifts in climate, rather than major changes in the total mass of the atmosphere. While direct, precise barometric measurements only date back to the mid-17th century (circa 1643), studies of historical climate events and proxy data indicate that while local pressures fluctuate (e.g., in Europe, with records from 1692, or in Iceland), the global average hasn't changed dramatically.
Key Findings on Atmospheric Pressure (Last 1000 Years):
Long-Term Stability: The total mass of the atmosphere has remained relatively constant, resulting in a consistent average sea-level pressure of roughly 1 bar.
Barometer Records: The first regular meteorological measurements began around the mid-1600s, with continuous data sets, such as those in Europe, beginning in the 18th and 19th centuries.
Extreme High Pressure: The highest sea-level air pressure ever recorded was 1083.8 mb (32.01 in. Hg) in Agata, Siberia, on December 31, 1968, caused by an extremely cold, dense air mass.
Extreme Low Pressure: The lowest non-tornadic atmospheric pressure ever measured was 870 hPa (0.858 atm; 25.69 inHg), during Typhoon Tip in the western Pacific Ocean on October 12, 1979.
Climate & Weather Fluctuations: Studies, including those analyzing 20th-century data and earlier records, show significant, though not permanently altering, fluctuations in atmospheric pressure associated with weather events, such as the 1862 Great Flood.
Future Projections: Research indicates that climate change-driven weather events (e.g., in the US Southwest) could be more extreme, with pressures associated with severe droughts potentially lasting 30-35 years, a phenomenon, while driven by temperature, with pressure implications.
Historical Data Limitations:
Direct, worldwide, and highly accurate barometer data is only available for the past ~300-400 years, with more robust data only available for the last 100-150 years. Therefore, for most of the last 1000 years, atmospheric pressure is inferred from climatological proxies rather than direct measurement.