A leading climate-change researcher expressed doubt that growing public fears over the link between extreme weather events and global warming have any basis in science.

Robert Livezey, chief of the Climate Services Division, Office of Climate, Water and Weather Services for the National Weather Service, spoke Wednesday at the 14th annual Operation Sierra Storm meteorological conference in Mammoth Lakes. He voiced concern that the ramifications of global warming on the numbers and severity of hurricanes, tornadoes, heat waves, damaging winds, floods and droughts had been exaggerated beyond their proven bounds.

There are "no convincing links" between trends in greenhouse gas concentrations in the atmosphere and trends in severe weather events, according to the scientist.

He went on to dispel many current myths about the presently understood effects of global warming.

Livezey said that, although there has been a recent shift toward more hurricane activity in the past decade, similar shifts are not unprecedented in human history.

Widespread fears about drought in the southwestern U.S. from atmospheric warming come at a time when the area has actually experienced a trend of higher average precipitation rates in recent years, according to Livezey.

North America has an overall trend of higher numbers of heavy precipitation events, but this tendency has not created significant increases in catastrophic flooding, in Livezey's estimation.

He also said that there is "No detectable trend in heat waves, yet" due to global warming, although the average global temperature is undoubtedly on the rise.

Livezey said the only effect of climate change that is completely certain is a rise in sea level, but even the rate of this rise is still under debate.

"There are uncertainties about how climate will change, but it will change," Livezey said.

These doubts are largely due to inaccuracies in the computer models used to predict how Earth's climate will change. Livezey stated that none of the current models take into account more than half of the variables that account for global weather patterns. "We need more basic science to improve these models," he said.

He added that only broad global weather pattern predictions are trustworthy using the current models, and that any specific predictions about local and regional effects of warming are highly suspect.

Livezey used the concern surrounding the long-term dependability of the Sierra snowpack as an example. He said the current trend in average snowfall is flat or slightly increasing.

Some resorts have experienced more precipitation falling as rain rather than snow in recent years, meaning these resorts are potentially "going to dry up earlier in the year," according to Livezey.

He cautioned about speculation over long-term local effects based on these reports though, because the global climate is an incredibly complex system. Simple, concrete answers about the change in climate of certain places like the Sierra are not yet confirmed by rigorous testing. Livezey believed to turn these pieces of anecdotal evidence into long-term certainties required a leap of faith that isn't based in science.