October 20, 2016

With a full quarter of the year left to record, climate scientists are already willing to bet their bottom dollar that 2016 will be the hottest year on record. Some of the unusual heat seen this year has probably been driven by short-term climactic cycles, but 2016 has been an exceptionally hot year in a streak of abnormally hot years. Most scientists attribute this worldwide trend to human-induced global warming.

Global warming has contributed to drought conditions in California, where rainfall totals in recent years are the lowest in the state’s recorded history. Dry lake beds, like this one in the Coyote Hills of northern California, are becoming an all-too familiar sight in the state. Credit: © Sheila Fitzgerald, Shutterstock

Global warming is an increase in the average temperature at Earth’s surface. People often use the term global warming to refer specifically to the warming observed since the mid-1800′s. Scientists estimate that Earth’s average surface temperature has risen by about 1.4 Fahrenheit degrees (0.78 Celsius degrees) since 1880. Researchers have also found that most of the temperature increase occurred from the mid-1900′s to the 2000′s.

The recent strong El Niño probably contributed to the record-shattering heat. An El Niño is a part of the interaction between Earth’s atmosphere and the tropical waters of the Pacific Ocean. An El Niño occurs about every two to seven years, and it can affect the climate throughout the world. The most recent El Niño ended in the spring of 2016. The event caused temperatures to surge. Eleven of the past 12 months have been the hottest months on record. July and August 2016 tied for the hottest months ever recorded.

Earth has continued to warm even in years without a strong El Niño effect. Every year of the 2010’s has been within the top 15 hottest years on record. 2015 ranked as the hottest ever, while 2014 came in second and 2013 was fourth. Of those years, only 2010 experienced a mild El Niño effect. Scientists think these record temperatures are the result of humans releasing massive amounts of gases such as carbon dioxide into the atmosphere.

Despite the end of the El Niño, Gavin Schmidt, the director of NASA’s Goddard Institute for Space Studies, stated that 2016 “seems locked in” to break 2015’s record temperatures. That year was 1.62 °F (0.90 °C) above the average annual temperature since 1900. Even if the rest of 2016 is unexpectedly cool, it should not be enough to counteract the heat of the first nine months. It would take an unprecedented climate anomaly to prevent 2016 from becoming the hottest year on record.