Hurricane Harvey lingered over south Texas for more than a week last September, dumping up to 60 inches of rain that left most of Houston underwater and resulted in 93 deaths.
The first tropical storm of the eastern Pacific hurricane season formed well off the coast of Mexico on Wednesday, AP reported, as forecasters said it's not a threat to land.
Slower-moving storms mean greater rainfall totals, as seen with Hurricane Harvey in Texas previous year.
The western North Pacific basin, where the strongest systems are referred to as typhoons and super typhoons, sees the most storms annually and has seen the most slowing, at 20%.
Study author James Kossin of the National Oceanic and Atmospheric Administration says Harvey is a great example of what he found.
Kossin's work was based on details of nearly 70 years' worth of storms, but he made no attempt to determine what was causing the slowdown.
"The storms will stay in your neighbourhoods longer", he said.
The speed of tropical cyclones around the world has decreased globally by about 10 percent since 1949.
Christina Patricola, a scientist with the climate and ecosystem sciences division of California's Lawrence Berkeley National Laboratory, called Kossin's work "important and new" and says she found it "pretty convincing".
To understand the relationship between climate change and hurricane speeds, Kossin analyzed the paths of 7,585 tropical cyclones from 1949 to 2016.
Kossin would actually agree on that point.
That's the real risk of a slower storm. The VIIRS image showed a better, more organized circulation center with consolidating banding of thunderstorms wrapping into a well-defined low level circulation center.
Therefore, it would make sense that if the flow around the hurricanes and typhoons is moving slowly, the storms will also be moving slower, which Kossin believes is what he is observing in the data. No storm from today will reproduce in quite the same way in the future. "Not quite like a cork in a stream, but similar", he said. "And when you start getting more and more lines of evidence that all point in the same direction, you get more confident in the answers".