"If you’re younger than 30, you’ve never experienced a month in which the average surface temperature of the Earth was below average. Each month, the US National Climatic Data Center calculates Earth’s average surface temperature using temperature measurements that cover the Earth’s surface. Then, another average is calculated for each month of the year for the twentieth century, 1901-2000. For each month, this gives one number representative of the entire century. Subtract this overall 1900s monthly average—which for February is 53.9F (12.1C)—from each individual month’s temperature and you’ve got the anomaly: that is, the difference from the average." - Todd Hoff