For the globe overall, last month turned out to be the second warmest June on record, data from NASA’s Goddard Institute for Space Studies show.
June of 1998, an intense El Nino year, retains the title for the hottest such month since record keeping began in 1880.
The warmth was not distributed equally around the globe, of course. A few regions were cooler than average. But as the map above from GISS shows, they were the exception, not the rule.
The blue and green colors show where temperatures were cooler than the long-term average, whereas the yellows, oranges and reds show the opposite. One area of note is Alaska, which experienced some particularly hot temperatures during the month.
According to the monthly U.S. State of the Climate report, released today by the National Climatic Data Center, Alaska experienced its third warmest June in the 96-year record. “A heat wave during the third week of the month brought temperatures in excess of 90°F to parts of the state, breaking daily record high temperatures at many locations,” the report states.
For the lower 48 states of the U.S. overall, the month came in as the 15th warmest. Temperatures were particularly high in the West. This likely contributed to the roughly 4,000 wildfires that blazed across more than 1.2 million acres during June, mostly in the West and Alaska. “The number of fires was below average, while the acreage burned was above average,” according to the report.
Another noteworthy detail from the U.S. report: “On a local basis, over three times as many record warm highs and lows occurred than record cold highs and lows.” (One caveat: The report cautions that the numbers are preliminary and could change.)
This is part of a broader trend documented by scientists. For example, a 2009 study showed that a warming climate was resulting in twice as many record high temperatures being recorded in the continental United States as record lows.
“Climate change is making itself felt in terms of day-to-day weather in the United States,” said Gerald Meehl, the lead author of the study and a senior scientist at the National Center for Atmospheric Research, quoted in an NCAR press release. “The ways these records are being broken show how our climate is already shifting.”
In the Northern Hemisphere overall, similar trends have been noted:
Based on a study by scientists at the Goddard Institute for Space Studies, this animation shows how the distribution of unusually warm days (red) and unusually cool days (blue) has shifted during summer in the Northern Hemisphere. Back in the 1950s, there were about an equal number — just what you’d expect with normal variation in the climate. But over time, the bell-shaped curve slides to the right, with unusually warm days far outnumbering cool ones.
Another way to picture what’s going on is to think about the human impact on climate as akin to loading a pair of dice. Without that impact, each throw of the climatic dice would produce a random result — and a nice bell-curve distribution of warmer- and colder-than-average days. But thanks to all of the carbon dioxide, methane, and other greenhouse gases we’ve been pumping into the atmosphere, we’ve made it much more likely that when the dice are thrown, the result will be unusual warmth.
I should point out that these trends are playing out against a contentious backdrop: The rise in the average annual temperature of the globe overall has plateaued. Skeptics claim that this debunks the idea that humans are having a significant impact on the climate.
But over the long run, the rise in global temperatures is clear. It’s just that the rise has occurred in something of a sawtooth pattern, with periods of little to no warming. Perhaps even more important, if the climate was not warming, we wouldn’t expect unusually warm days to outnumber unusually cool ones so dramatically.