This year is on track to be a record 1 degree Celsius (1.8 degrees Fahrenheit) 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 (3.6 degrees F) that governments have set as a limit to avoid dangerous levels of warming.
"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," says meteorologist Stephen Belcher. Meanwhile, the World Meteorological Organization (the UN's weather agency) reports 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 ppm in 2013, the WMO says. Pushed by the burning of coal, oil, and gas for energy, global CO2 levels are now 143% higher than before the industrial revolution. Scientists say that's the main driver of global warming. (Read more global warming stories.)