(Bloomberg) -- Climate change can make heat waves more likely and more severe, according to a study in the Bulletin of the American Meteorological Society that found fewer clear links to extreme weather such as drought and storms.

Twenty independent teams looked at 16 events around the world in 2013, including in the U.S., Australia and Europe. They found there is evidence that the burning of fossil fuels has increased the risk for extreme heat waves.

“How human influence affected other types of events such as droughts, heavy rain events and storms was less clear, indicating that natural variability likely played a much larger role in these extremes,” they wrote.

Stephanie C. Herring, with the National Climatic Data Center, an Asheville, North Carolina-based unit of the National Oceanic and Atmospheric Administration, was lead editor of the study. It was conducted in part because of growing public curiosity as to whether climate change plays a role in various severe weather events, such as snowstorms.

“This demand for information is a challenge for the scientific community, especially when it is requested shortly after an event when planning is under way to lessen the risk of future events,” the report said. “It is difficult to quantify the often multiple causal factors among large weather variability.”

The study concluded that climate change increased the chances of heat waves such as those last year in Australia, New Zealand, Japan, Korea and China.

Colorado Flooding

However, the chances of heavy rainfall like the deluge that caused flooding in Boulder, Colorado, last year, are probably lower because of human-caused weather changes. A blizzard that struck South Dakota last October also has a lower chance of recurring when considering climate change, the study said.

A large wind storm named Christian that swept northern Europe and the U.K., as well as a blizzard in the Pyrenees, couldn’t be conclusively blamed on climate change, the paper said.

“When human influence for an event cannot be conclusively identified with the scientific tools available today, this means that if there is a human contribution, it cannot be distinguished from natural climate virility,” NOAA said.

As computer models get better and tools improve, there may be more answers in the future, said Thomas Karl, director of the data center.

“That is how science evolves,” he said.

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