As Hurricane Harvey approaches Texas, an old argument has again resurfaced about whether climate change is to blame.
In the past, scientists have had a rather unsatisfying answer for both environmentalists and skeptics, essentially saying that while climate change increases the frequency and severity of extreme weather, no individual event could be attributed to it.
But that may be changing.
Climate scientists now say that they can use models and historical data to evaluate with increased precision how global warming has affected the odds of a given individual weather event.
Known collectively as the World Weather Attribution group, a group of scientists formed in 2014 to conduct studies on the subject, developing a series of steps they have worked to perfect for case studies. The team begins every project with an announcement that it will undertake the project and a promise to publish the results, even if the impact of climate change on a particular event is shown to be negligible.
The researchers use both observational data and climate models to double check results.
In the U.S., observational data dates back more than a century from thousands of weather stations and provides a historical record of how the likelihood of extreme weather has changed occurred over time. The climate models go back further, essentially creating alternate realities that could have played out under prescribed conditions over centuries.