Are the deadly Kentucky tornadoes linked to climate change?
Tornadoes that tore across America this week killed at least 74 people in Kentucky and has left hundreds homeless.
Kentucky Governor Andy Beshear said that the death toll was likely to rise as 109 people remained missing.
But are these tornadoes linked to climate change?
Meteorologist Michael Mann of Penn State told USA Today: "The latest science indicates that we can expect more of these huge (tornado) outbreaks because of human-caused climate change.”
Meteorologists believe that the warm, spring-like temperatures may have helped create the warm, moist conditions which form thunderstorms - leading to tornadoes.
Read more: Why economists worry that reversing climate change is hopeless
John Allen, Associate Professor of Meteorology, Central Michigan University says in an essay for The Conversation: “Projections suggest that stronger, tornado-producing storms may be more likely as global temperatures rise, though strengthened less than we might expect from the increase in available energy.
“In a recent study, colleagues and I found that the rate of increase in severe storm environments will be greater in the Northern Hemisphere and that it increases more at higher latitudes.
Allen says he believes that warming temperatures will lead to more environments that are favourable for the formation of tornadoes.
Allen says: “In the United States, our research suggests that for each 1 degree Celsius (1.8 F) that the temperature rises, a 14-25 percent increase in favourable environments is likely in spring, fall, and winter, with the greatest increase in winter.
“This is driven predominantly by the increasing energy available due to higher temperatures. Keep in mind that this is about favourable environments, not necessarily tornadoes.”
Dan DePodwin, the director of forecast operations for AccuWeather told USA Today: “Because we know the climate’s warming, there’s usually the potential for more moisture and more sort of rich moisture to be present at different times of the year than had been the case previously. In order to have an outbreak like this, you need warm, moist air, and in this case, it comes from the Gulf of Mexico."
This year’s UN climate change report warned that extreme weather events like heatwaves and droughts which previously would have happened every 50 years could soon happen every four.
The report was the first to quantify the likelihood of extreme events across a wide variety of scenarios.
The researchers also warned that other ‘tipping point’ events are a possibility.
The researchers wrote: “Abrupt responses and tipping points of the climate system, such as strongly increased Antarctic ice sheet melt and forest dieback, cannot be ruled out”.
Dr. Robert Rohde, Lead Scientist of Berkeley Earth said: “What were once-in-50-year heat extremes are now occurring every 10 years.
“By a rise of two degrees celsius, those same extremes will occur every 3.5 years.”
The report found that (for example) once-in-a-decade heavy rain events are already 1.3 times more likely and 6.7% wetter, compared with the 50 years leading up to 1900 when human-driven warning began to occur.
Droughts that previously happened once a decade now happen every five or six years.
Xuebin Zhang, a climatologist with Environment Canada in Toronto warned that as the world warms, such extreme weather events will not just become more frequent, they will become more severe.
Zhang said that the world should also expect more compound events, such as heat waves and long-term droughts occurring simultaneously.
Zhang said, “We are not going to be hit just by one thing, we are going to be hit by multiple things at the same time.”
Watch: Accuweather estimates $18 billion damage from multi-state tornado outbreak