A new study says human-caused climate change made Atlantic hurricanes about 18 mph stronger in the last six years.

A new study released Wednesday found that climate change intensified recent hurricanes by 18 miles per hour.  The study, titled “Human-caused ocean warming has intensified recent hurricanes,” was

For three storms, including this month's Rafael, the climate change factor goosed wind speed so much that the winds increased by two storm categories.

Human-caused climate change made Atlantic hurricanes about 18mph stronger in the last six years, a study shows. For most of the storms – 40 of them – the extra push from warmer oceans made the storms jump an entire hurricane category,