2018 is only halfway over, but a troubling climate change trend is already apparent

Earth is in the midst of a 40-year-long accelerated warming trend spurred on by human-caused climate change, and 2018 isn’t helping.

Scientists at NASA’s Goddard Institute for Space Studies (GISS) and Columbia University showed this week that the average surface temperature on Earth between January and June this year was the third hottest half-year on record, since good record keeping began long ago, in 1880.

But the trend goes much deeper than that.

The first half of the last four years — 2015, 2016, 2017, and 2018 – all take the top four hottest-recorded January to June periods ever documented. 

A single record-breaking month or year can be telling, but it’s not nearly as scientifically meaningful as these longer-term trends.

“When a record is broken once, it’s a fluke. When it happens again, it’s a coincidence. When it happens three times, it’s a trend, but when it happens every single year, it’s a movement,” Sarah Green, an environmental chemist at Michigan Technological University, said over email.

As NASA’s maps show, this heating trend is occurring all over the planet, showing how the entire global climate has been disrupted by potent heat-trapping gases in the atmosphere, notably carbon dioxide.

“In a stable climate, one place is warmer than normal while another is colder,” said Green. “The GISTEMP global maps show that is no longer the case; it’s hotter pretty much everywhere.”

This includes Earth’s expansive oceans, which are much more absorbent that Earth’s rocky surface. Over 90 percent of Earth’s accumulating heat gets trapped by the seas.

“The inexorable heating of the oceans is especially worrying,” said Green. “Land temperatures fluctuate with a shift in the wind direction or a passing cloud, but the increasing temperature of the surface ocean shows that greenhouse gasses are trapping more and more heat on Earth.”

Overall, January through June temperatures during the first halves of the last four years were about 2 degrees Fahrenheit, 1.1 degrees Celsius, higher than preindustrial times, Makiko Sato, a NASA GISS scientist, said over email.

“It shows global warming is really happening,” said Sato.