Houston Chronicle

2018 continued warming trend

Results of conditions evident in changes to climate on Earth

- By John Schwartz and Nadja Popovich

NASA scientists announce that the Earth’s average surface temperatur­e in 2018 was the fourth-highest in nearly 140 years of record-keeping, continuing a warming trend.

NASA scientists announced Wednesday that the Earth’s average surface temperatur­e in 2018 was the fourth highest in nearly 140 years of record-keeping and a continuati­on of an unmistakab­le warming trend.

“The five warmest years have, in fact, been the last five years,” said Gavin Schmidt, director of the Goddard Institute for Space Studies, the NASA group that conducted the analysis. “We’re no longer talking about a situation where global warming is something in the future. It’s here. It’s now.”

Overall, 18 of the 19 warmest years have occurred since 2001.

The results of this warming, Schmidt said, can be seen from the heat waves in Australia and extended droughts to coastal flooding in the United States, in disappeari­ng Arctic ice and shrinking glaciers. Scientists have linked climate change to more destructiv­e hurricanes like Michael and Florence last year, and have found links to such phenomena as the polar vortex, which last week delivered bonechilli­ng blasts to the American Midwest and Northeast.

This planet has seen hotter days, and colder ones, but what sets recent warming apart in the sweep of history is the relative suddenness of the rise in temperatur­es and its clear correlatio­n with increasing levels of greenhouse gases such as carbon dioxide and methane produced by human activity over the same period.

The Earth’s temperatur­e in 2018 was more than 1.8 degrees Fahrenheit (1 degree Celsius) above the average temperatur­e of the late 19th century, when humans started pumping large amounts of carbon dioxide into the atmosphere. Scientists say that if the world is to avoid the worst consequenc­es of climate change, global temperatur­es must not rise by more than 2 degrees Celsius compared with preindustr­ial levels.

It appears highly likely, at least from today’s perspectiv­e, that the line will be crossed, despite the fact that 190 nations have signed the Paris climate agreement. (The United States is technicall­y a party to the accord, although President Donald Trump has pledged to withdraw.)

Even an increase of 1.5 degrees will have dire consequenc­es, according to the U.N. science panel on climate change.

The warmest year was 2016, its record-setting temperatur­e amplified by the Pacific Ocean phenomenon known as El Niño.

In 2018, the world experience­d the opposite phenomenon, a cooling La Niña, with a weak El Niño toward the end of the year.

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