NASA’s assessment differs slightly from a report released Thursday by NOAA, which also maintains a global temperature dataset that uses somewhat different methods. NOAA concluded that last month was the sixth hottest June on Earth, also dating back to 1880.
Much of the difference likely lies in the two datasets’ treatment of the polar regions, experts from NASA and NOAA said. Currently, the NASA dataset contains more entries from the Arctic and Antarctica, the latter of which showed very high temperatures in June. But both data sets show that the globe has warmed dramatically, especially since around 1980.
“Even though we rank slightly differently, we’re still telling the same story here,” said Ahira Sánchez-Lugo, NOAA’s National Centers for Environmental Information (NCEI) scientist and lead author of the Climate Report. agency worldwide.
The two agencies use around 10,000 land temperature stations around the world – in addition to a wide range of ocean measurements – to calculate the global average temperature.
Sánchez-Lugo said warming has been particularly dramatic over the past month in parts of Europe and Asia. She noted that while the summer months are always characterized by heat waves, “we are seeing these types of heat waves occurring more intensely and more frequently.”
Also, while we tend to think of summer as having the longest days of the year and the most sunshine, Sánchez-Lugo said nighttime temperatures are also rising.
“During the night, we are supposed to be able to cool off. Not just us, but animals, crops, everything,” Sánchez-Lugo said. “When that doesn’t happen, that’s when we get heat exhaustion, or heat illness, because the nights don’t get as cold as they used to.”
The scientists point out that the real message is in the totality of the data, not just one month’s data.
“The key indicators of global warming are long-term trends, and this month’s anomalies are consistent with that upward trend,” said Gavin Schmidt, who directs NASA’s Goddard Institute for Space Studies, which produces the dataset in question.
“Exact rankings for any month are subject to more uncertainty, and while they may attract attention, it’s the underlying trend that matters.”