“The decade that just ended is clearly the warmest decade on record,” said Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies in New York. “Every decade since the 1960s clearly has been warmer than the one before.”

During 2019, the average temperature across global land and ocean surfaces was 1.8 degree Fahrenheit (0.98 degree Celsius) above the 20th-century mean, with 95% certainty, according to the NASA calculations. The NOAA scientists calculated the average global temperature as 1.71 degrees F (0.95 degree C) above the average for 1901 to 2000. Each agency uses slightly different data sets and techniques to arrive at their results.

Their calculations are in line with a recent assessment by the European Union’s Copernicus Climate Change Service, operated by the European Centre for Medium Range Weather Forecasts, which last week ranked 2019 as the second-warmest year on record.

All told, 10 of the warmest years in their records occurred in the past decade, the NOAA and NASA scientists said Wednesday.

Since the 1880s, the average global surface temperature has risen about 2 degrees F (1 degree C), according to scientists at NASA’s Goddard Institute.

Much scientific work attributes rising temperatures to greenhouse gases such as carbon dioxide, methane and nitrous oxide from fossil fuel emissions, agriculture and cement production, and land use changes, though some question the connections. Satellite studies of solar energy output since 1978 show the Sun doesn’t appear to be responsible for the warming trend observed over the past several decades, NASA scientists have reported.

Atmospheric carbon-dioxide levels increased in 2019, reaching a seasonal peak of 414.7 parts per million (ppm) at NOAA’s Mauna Loa Atmospheric Baseline Observatory. It was the seventh consecutive year of global increases in concentrations of carbon dioxide, according to data published by NOAA and Scripps Institution of Oceanography.

The warmest year to date was 2016, when an unusually strong El Nino current in the Pacific Ocean boosted warming world-wide by influencing the formation of high- and low-pressure weather systems, trade winds and rainfall. In 2019, a relatively weak El Nino subsided early in the year, the NASA and NOAA scientists said.

Ocean heat during 2019 was the highest on record, NOAA scientists said.

Weather dynamics often affect regional temperatures differently, so not every area on Earth experienced the same temperatures last year.

In 2019, Europe recorded its warmest calendar year, experiencing two of the most intense heat waves in its modern history during June and July, according to the Copernicus Climate Change Service, which provides climate analytics to EU member countries. High temperatures set heat records in six countries, according to the Weather Channel. Paris registered a high temperature of 108.7 degrees F (42.6 C) in July, breaking a 72-year-old record by 4 degrees F.

For the entire U.S., NOAA scientists found the annual mean temperature for 2019 was the third-warmest on record, while Alaska, Georgia and North Carolina experienced the warmest year in their history. The average temperature across the continental U.S., excluding Alaska, was the 34th-warmest in 126 years, the scientists said.

Alaska also experienced destructive wildfires that, when combined with those in California, caused damages in excess of $1 billion, NOAA scientists said. By NOAA’s count, 13 other weather-related billion-dollar disasters struck the U.S. last year, including Hurricane Dorian, tornados, hailstorms and flooding across 15 states.

After adjusting for inflation, the U.S. experienced more than twice the number of billion-dollar weather disasters during the past decade (119) compared with the 10 years that preceded it (59), the NOAA scientists said.

Write to Robert Lee Hotz at sciencejournal@wsj.com