How much warmer than 1880-1900?

Source: NASA GISS Surface Temperature Analysis (GISTEMP v4), 2°×2° grid with 1,200 km smoothing, anomalies rebased from 1951-1980 to each cell's own 1880-1900 average for that calendar month. NASA's record begins in 1880, so 1880-1900 stands in for the 1850-1900 period used by the IPCC. Cells without at least ten baseline years (27% of cells: Antarctica, the Amazon, central Africa, the Sahara and Arabia, the deserts of western China, the Arctic coasts and much of the Southern Ocean) use the average of their latitude band, so the pattern there is NASA's but the level is approximate. Within about 800 km of the South Pole NASA's grid carries a single value. Land share is area-weighted and counts Antarctica. Population is the 2025 GHS-POP grid from the EU Joint Research Centre, held fixed for every year, so the population figure reads as the share of today's people. Early years have thin coverage; the note above the legend says how much of the land and population had data. A single month at one place swings a lot from year to year; the 10-year average is closer to how the 1.5°C target is defined. The 1951-1980 option shows NASA's anomalies as published, with no rebasing and no latitude-band fill-in. It starts in 1951, the first year of NASA's baseline, so it uses no data from before then; its first 10-year average is 1957. That period has far more measurements than 1880-1900, but it was already warmer, so the same 1.5°C line is a higher bar and the shares above it are lower. The places that warmed most are the same under both. Coastlines and borders from Natural Earth.