January 2026 was ranked as the world's fifth-warmest January on record, going back to what year?

January 2026 was recorded as the world's fifth-warmest January, a ranking that relies on a comprehensive dataset stretching back to 1850. The year 1850 is generally considered the starting point for reliable global temperature records because it marks the period when widespread and consistent thermometer-based measurements began across enough of the planet to provide a meaningful global average. Before this time, temperature data was far sparser, making it challenging to accurately assess global trends.

Today, major scientific organizations like NOAA (National Oceanic and Atmospheric Administration) and Europe's Copernicus Climate Change Service meticulously collect and analyze temperature data from thousands of land-based weather stations, as well as ships and buoys across the oceans. These measurements are then compared against a long-term average, often from a baseline period like 1951-1980, to calculate "anomalies," which show how much warmer or cooler a particular period is compared to the norm. This rigorous process allows scientists to track subtle but significant shifts in Earth's climate over time.

The fact that January 2026 ranks among the top five warmest Januarys on record underscores a clear long-term warming trend. Such rankings are not isolated events but rather fit within a broader pattern of rising global temperatures observed over the past few decades. This consistent warming across months and years is a key indicator of ongoing climate change, driven primarily by human activities and the emission of heat-trapping greenhouse gases into the atmosphere.