The past five years on Earth have been the warmest in the modern climate record, and will be remembered for their fatal legacy of extreme weather events such as Hurricane Maria in Puerto Rico, which was one of the deadliest in American history.
This is according to the National Aeronautics and Space Administration (NASA) and National Oceanic and Atmospheric Association (NOAA) which announced their annual global temperatures and climate trends for 2018 on Wednesday. Both agencies are record keepers of the world’s temperature data, and independently publish the annual “State of the Climate” report based on ground and satellite measurements.
2018 ranked as the fourth-hottest year since 1880, and bookended a 42-year-long stretch of global land and ocean temperatures being above the 20th century average.
Last year also witnessed 14 separate climate and weather disasters in the US, each accounting for at least $1 billion in direct losses, making 2018 the fourth worst year since 1980 in terms of cost and frequency of these events.
“The planet is warming. The long term trends are extremely robust, and there’s no question about those trends existing in the data, no matter how you slice it,” Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, said on a Wednesday press call.
Last year was part of historic warming phenomenon driven overwhelmingly by greenhouse gas emissions from human activity, the report noted.
Since the advent of the modern temperature record in 1880, that warming trend has resembled someone “riding up an escalator over time and jumping up and down,” Deke Arndt, chief of NOAA’s climate monitoring branch at the National Centers for Environmental Information, said on the press call.
In other words, while temperatures are increasing overall, atmospheric factors such as El Niño and La Niña have caused some flux.
As a rule of thumb, Schmidt explained, El Niño can result in warmer global mean temperatures the subsequent year. A year kicked off by La Niña may see cooler temperatures. Without these two forces coming into play, 2018 would have been the third warmest year on record.
Massive volcanic eruptions, such as the 1991 explosion of Mount Pinatubo in the Philippines, have also historically caused short cooling events.
Perhaps more memorable than its temperature ranking (which scientifically speaking, climate researchers “are not totally excited by,” Schmidt admitted) are last year’s portfolio of extreme weather events.
Typhoon Yutu was the strongest typhoon on record to hit the Mariana Islands in the Pacific Oceans, and left behind a horrific aftermath. Temperatures in the Algerian city of Ouargla soared to 124 degrees Fahrenheit in July, setting a new record for the African country. Wildfires throughout the American west accounted for $24 billion of the country’s $91 billion in direct losses caused by last year’s most economically devastating disasters.
Some of these events saw “inland flooding and extreme heat, and those are clearly increasing in the climate system,” said Arndt who warned against ignoring economic factors or Sunbelt migration as contributing factors to the damage caused by extreme weather events.
In the Arctic, which is warming two-to-three times faster than the global mean, its sea ice maximum or growth season in 2018 was the second smallest on record.
Another theme that continued to emerge last year, according to the report, was increasingly hotter morning temperatures in the US. In a warming world, it is anticipated that “we would see increases in overnight temperatures [begin to] outpace increases in daytime temperature,” Arndt said.
In the US, the average direct losses due to these events has ticked upward in recent decades. The federally produced National Climate Assessment, published late last year, also found that “new and stronger evidence” confirms the connection of some extreme weather to human activities.
Last year was “quite clearly the fourth warmest year in our record,” Schmidt said, “which goes back to 1880 and was probably warmer than many hundreds of years before that.”