Greenhouse gases tilt odds toward record warmth
It’s highly unlikely Earth would have seen a three-year run of record global temperatures without its blanket of human-caused greenhouse gases, scientists concluded in a new study that tried to pin down the relationship between record warmth and human-caused global warming.
Without the warming effect of carbon dioxide, methane and other heat-trapping pollutants, there’s only a 0.03 percent chance that there would be three consecutive years of record temperatures; when the warming effects of greenhouse gases are added into the equatio, the odds of three consecutive record-breaking years happening any time since 2000 rises to as high as 50 percent, according to the new study.
In 2016, the average global temperature across land and ocean surface areas was 0.94 degrees Celsius (1.69 degrees Fahrenheit) above the 20th century average of 13.9 degrees Celsius (57.0 degrees Fahrenheit), according to NOAA. The average surface temperature of the planet has risen about 1.1 degrees Celsius (2.0 degrees Fahrenheit) since the late 19th century, and the past 35 years have seen a majority of the warming, with 16 of the 17 warmest years on record occurring since 2001, according to NASA.
“With climate change, this is the kind of thing we would expect to see. And without climate change, we really would not expect to see it,” said Michael Mann, a climate scientist at Pennsylvania State University in State College, Pennsylvania, and lead author of the new study published in the journal Geophysical Research Letters.
According to Mann, the new study considers statistical clusters of years that are linked by natural factors like El Niño, the solar cycle and volcanic eruptions. If human-caused climate change is not considered, the warming observed in 2016 would have about a 1-in-a-million chance of occurring, compared with a nearly 1-in-3 chance when anthropogenic warming is taken into account, according to the study.
The results make it difficult to ignore the role human-caused climate change is having on temperatures around the world. Rising global temperatures are linked to more extreme weather events, such as heat waves, floods, and droughts, which can harm humans, animals, agriculture and natural resources, he said.
“The things that are likely to impact us most about climate change aren’t the averages, they’re the extremes,” Mann said. “Whether it’s extreme droughts, or extreme floods, or extreme heat waves, when it comes to climate change impacts … a lot of the most impactful climate related events are extreme events. The events are being made more frequent and more extreme by human-caused climate change.”