An iceberg floating in Arctic waters
An iceberg floating in Arctic waters. Credit: NOAA, CC BY 2.0

July 2019 might have broken the record for highest monthly surface air temperature, according to a report from a European climate monitoring agency. Temperatures in Alaska, Greenland, Siberia, and Antarctica were the highest relative to a 30-year average.

“July has re-written climate history, with dozens of new temperature records at local, national and global level.”

“July has re-written climate history, with dozens of new temperature records at local, national and global level,” Petteri Taalas, Secretary-General of the World Meteorological Organization, said in a statement.

The Copernicus Climate Change Service (C3S) released the report on 5 August. The report shows that by one metric, July 2019 surpassed the previous record holder for hottest month ever, July 2016, by 0.4°C.

July’s temperature record comes on the heels of reports of Antarctic sea ice extent being the lowest on record, “unprecedented” Arctic wildfires, sweeping heat waves on multiple continents, and a Greenland ice sheet losing 12.5 billion tons of water in a single day.

Arctic Highs, Very Few Lows

The C3S report is a preliminary analysis based on a monthly weather data set provided by the European Centre for Medium-Range Weather Forecasts. The data set includes measurements from satellites, ships, aircraft, and ground-based weather stations around the world. On the basis of these data, “July was about 0.56 °C degrees above average,” according to a C3S statement.

“This is close to 1.2°C above the pre-industrial level as defined by the Intergovernmental Panel on Climate Change (IPCC),” C3S officials state. The IPCC recommended a warming limit of 1.5°C above preindustrial values, averaged over 30 years, to reduce the impacts of global climate change.

Map of the surface air temperature anomaly for July 2019 relative to the July average for the period 1981–2010 for the whole globe (left) and for Europe (right). Click image to view larger version. Credit: ECMWF, Copernicus Climate Change Service

Arctic regions experienced very high temperatures in July relative to the most recent 30-year reference period (1981­–2010), in keeping with long-term global warming trends. The report highlights Alaska, Baffin Island, Ellesmere Island, Greenland, and parts of Siberia as having particularly warm temperatures. Western Europe, much of the United States, Iran, and the central Asian republics were also hotter than normal.

Antarctica experienced both the highest and lowest deviations from average air surface temperature in July. Temperatures in West Antarctica, the Antarctic Peninsula, the Ross Ice Shelf, and the Ross Sea rose to around 10°C above average. Parts of the Weddell Sea and nearby lands in East Antarctica experienced temperatures a few degrees cooler than average.

Temperatures in midwestern Canada and eastern Europe were also slightly below average. Ocean air temperatures were, overall, warmer than average despite a few areas of cooler-than-average temperatures.

On Track for a Consecutive Five Hottest Years

The temperature difference between July 2019 and July 2016 was marginal, C3S cautions, and future data may show that July 2016 is still the record holder. The agency will release a more comprehensive climate report for July later this month when data from other agencies, including some in the United States and Japan, become available.

Previous reports from C3S show that, so far, each month in 2019 has been among the top four hottest of that month on record. If the trend continues, 2015–2019 will be the five hottest years on record whether or not July 2019 comes out on top.

“This year alone, we have seen temperature records shattered from New Delhi to Anchorage, from Paris to Santiago, from Adelaide and to the Arctic Circle,” United Nations Secretary-General António Guterres said in a statement. “If we do not take action on climate change now, these extreme weather events are just the tip of the iceberg. And, indeed, the iceberg is also rapidly melting.”

—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer


Cartier, K. M. S. (2019), July may turn out to be the hottest month in recorded history, Eos, 100, Published on 09 August 2019.

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