Global temperatures approach milestone

Scientists blame the rise mostly on human activities.

STOCKHOLM— This year is on track to be a record 1.8 degrees Fahrenheit

1 degree Celsius hotter

— — than the 19th-century average, hitting a symbolic milestone in the temperature rise that scientists blame mostly on human activities, Britain’s weather service said Monday.

To measure global warming, scientists compare today’s temperature level with that of the latter part of the 19th century, when record keeping began and before humans started burning fossil fuels on a large scale, releasing heat-trapping carbon dioxide into the air.

A rise of 1 degree C is important because it’s halfway to the 2 degrees C — or 3.6 degrees F — that governments have set as a limit to avoid dangerous levels of warming.

The British Met Office said global temperatures from January to September were 1.02 C above the 1850-1900 average, adding that the rest of the year is expected to remain hot because of the El Nino weather phenomenon.

“We’ve had similar natural events in the past, yet this is the first time we’re set to reach the 1 degree C marker and it’s clear that it is human influence driving our modern climate into uncharted territory,” said Stephen Belcher, director of the Met Office Hadley Centre for climate science.

Met Office officials noted it doesn’t mean every year from now will be at least 1 degree warmer, as natural variability will still play a role.

The World Meteorological Organization, the U.N. weather agency, is expected to release its assessment of this year’s temperatures later this month, combining the Met Office numbers with data from NASA and the National Oceanic and Atmospheric Administration in the U.S.

On Monday, WMO reported that levels of carbon dioxide and methane, the two most important greenhouse gases, reached record highs last year, continuing the warming effect on the world’s climate.

Carbon dioxide levels rose to nearly 398 parts per million, from 396 in 2013, WMO said.

The CO2 level fluctuates throughout the year and the monthly average crossed the symbolic 400 parts per million threshold in March 2015. The WMO said the annual average “is likely to pass 400 ppm in 2016.”

Pushed by the burning of coal, oil and gas for energy, global CO2 levels are now 143 percent higher than before the industrial revolution. Scientists say that’s the main driver of global warming.

WMO said methane levels reached a new high of about 1,833 parts per billion in 2014.