"Scientific" American claims that human "fingerprints" are showing up on individual weather events; fails to tell us exactly what this means

Storm Warnings: Extreme Weather Is a Product of Climate Change: Scientific American

In this year alone massive blizzards have struck the U.S. Northeast...
...Scientists used to say, cautiously, that extreme weather events were "consistent" with the predictions of climate change. No more. "Now we can make the statement that particular events would not have happened the same way without global warming," says Kevin Trenberth, head of climate analysis at the National Center for Atmospheric Research (NCAR) in Boulder, Colo.
...
The second line of evidence comes from a nascent branch of science called climate attribution. The idea is to examine individual events like a detective investigating a crime, searching for telltale fingerprints of climate change. Those fingerprints are showing up...

This new science is still controversial. There's an active debate among researchers about whether the Russian heat wave bears the characteristic signature of climate change [What, exactly, is that supposed to mean?] or whether it was just natural variability, for instance. Some scientists worry that trying to attribute individual events to climate change is counterproductive in the larger political debate, because it's so easy to dismiss the claim by saying that the planet has always experienced extreme weather. ...[Nashville-based author and environmental journalist Amanda Little] "Climate change translates into mold on my baby's crib..."...In her own basement her family's belongings bobbed like debris in a pond.