In late September of 2015, residents of Miami woke up to find their streets inundated with several feet of water. But the flooding wasn’t brought by intense rainfall or a tropical storm — it was the result of historically high tides combined with rapidly rising sea levels. In other words, the flooding was due — at least in part — to climate change.
That’s the conclusion that the National Oceanic and Atmospheric Administration (NOAA) reached in its annual analysis of how climate change did — or did not — increase the likelihood of key weather events throughout the year. The report, released Thursday, looked at 30 “strange” weather events that took place throughout 2015, from the sunny day flooding in Florida to extremely cold weather in the Northeast. Of those 30 events, NOAA scientists found that 24 of them had been influenced by climate change.
“It has to be measureable,” NOAA scientist Stephanie Herring, co-editor of the report, told the Associated Press, explaining the study’s methodology. “It has to be detectable. There has to be evidence for it and that’s what these papers do.”
Heat waves, wildfires, and the sunny day flooding in Miami were all linked to climate change. Other events, like extreme downpours in Nigeria and India, and extremely cold weather in the northeastern United States, did not exhibit signs of climate change (though there has been some debate about the influence of climate change in the 2015 cold snap that brought record lows to much of the Northeast).
The NOAA report, which was worked on by 116 scientists from around the world, did not seek to determine whether climate change “caused” any of the extreme weather events, but rather, whether climate change made the events more likely. It’s a distinction that might seem like splitting hairs, but it’s actually an important one — think of it like the odds of a basketball player making a basket from various positions on the court. If the player started at half court, she might miss most of her shots, but she would still make a few baskets every once in a while. If she took a step forward, she would make a few more baskets. If she took steps forward until she was right under the hoop, she would make far more baskets than when she had been back at half court. The steps that the player is taking, in this case, are like climate change — each step towards the basket makes it more likely that the ball will go in, but it’s impossible to say that the step is the thing that caused the ball to go in, since she would have made baskets at half court some of the time.
It’s the same idea with the relationship between heat waves and climate change, for example.
“Even without climate change, there has always been heat waves,” Kevin Trenberth, a senior scientist with the National Center for Atmospheric Research, told ThinkProgress back in 2015. “It just relates to the right meteorological setup.”
Still, there is a growing body of scientific research that suggests that climate change is making heat waves more likely.
“The overwhelming scientific consensus is, first of all, extreme events are influenced by climate change today and, second of all, the clearest and strongest scientific evidence is that it has an influence in particular on heat events,” Stephanie Herring, a scientist with NOAA’s National Centers for Environmental Information, told ClimateWire.
2015 saw a series of devastating and record-breaking heat waves across the planet, including a heat wave in India that ranks as the 5th deadliest in world history. Temperatures reached 111°F (44°C) in New Delhi, hot enough to melt pavement, according to NOAA. All told, the heat wave killed at least 2,300 people.
Scientists are very confident that climate change makes deadly heat waves more likely. In the case of the 2015 heat wave that broke temperature records across the European continent, scientists concluded that climate change played a “significant” role, making the heat wave conditions twice as likely to occur as opposed to a scenario without climate change.
The NOAA report also found that wildfires in Alaska had the fingerprint of climate change. Wildfires are another weather event that scientists are increasingly sure are made more likely by climate change. A recent study found that temperatures in forested parts of the west increased about 2.5 degrees Fahrenheit since 1970, which caused the areas to become increasingly dry — that, in turn, created the kind of environment in which wildfires could more easily spark.
While the report did not find the record-cold snap experienced by the northeastern United States in the winter of 2015 to be symptomatic of climate change, other scientific studies have suggested that the polar vortex conditions that bring seriously cold air to the northeastern United States might be related to a warming Arctic — one of the most visible impacts of climate change. As climbing global temperatures contribute to a decrease in Arctic ice — and an increase in ocean water — the way the region absorbs and reflects heat from the sun changes. Ice reflects heat quickly, whereas water absorbs heat and releases it more slowly back into the local atmosphere. That might cause the polar vortex — also known as the polar jet stream, which is basically a stream of cold air that swirls from west to east around the Earth’s poles — to weaken near the Arctic, driving cold air down to lower latitudes.
Climate-denying politicians in Congress — and, come January 20, the White House — have used cold weather in the past in an attempt to disprove the concept of climate change. These arguments, however, show a deep misunderstanding of earth science — climate is the long-term average of atmospheric conditions, while weather simply refers to what is happening at a given place at a given time. All long-term trends point to a world that is markedly warmer than it was 100 years ago. 2016 is likely to be the hottest year on record, which would mean that of the 17 hottest years on record, 16 have occurred since 2000.
The distinction between weather and climate, however, seems unlikely to sway climate-deniers, who increasingly try to argue that the science on climate change is far from settled. And while the NOAA report shows that there is still some debate in the scientific community as to specific consequences of climate change — whether extreme cold can be attributed to a weakening Arctic jet stream, for example — there is no debate on whether climate change is real and happening. An overwhelming majority of publishing climate scientists agree that climate change is both real and man-made.