There are people making all kinds of claims about global warming. Some backed by scientific research, some pure conjecture. As temperatures rise, there will be more intense storms. This study shows some evidence that it has not happened yet. That does not mean it's not going to happen or that global temperatures are not rising.
The facts are indisputable. Global temperatures are rising, glaciers are melting, and C02 content in the atmosphere is rising.
IMHO, it is unrealistic to expect that nations of the world will take the kind of actions need to seriously lower C02 content in the atmosphere. It's just not political or economically feasible. Scientist can not accurately predict what will occur nor when. Even if we drastically reduce the amount of C02, we don't know if the process can be reversed. In fact we don't know for sure it can be stopped at all. I think governments of the world will ignore scientists until they have indisputable proof. At that time, we be dealing with the results of global warming not the prevention.
The evidence is the opposite. As the world warms the violence of storms decreases. We have a wonderful analog for this in the equatorial belt. It is very warm along the equator and there are constant mild rain storms. There is very little major storm activity in the equatorial tropics.
To get violent storms you need the interaction between warm and cold air masses.
As far as the rest, yes CO2 is going up but man only produces around 5% of the total CO2 budget and the concentration of CO2 in the atmosphere is less then 1% of the total air mass. Glaciers are also advancing worldwide though the warmists won't admit to it. Global temperatures were rising from the end of the '70's up until 1998 and then they moderated and now it appears we are entering the next cooling phase that will last for the next 20 to 30 years. All part of the normal cycles of warming and cooling that have been going on since the world came out of the last ice age.
Thunderstorms develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes. Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather pattern. Several states may be affected by numerous severe thunderstorms and tornadoes.
During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours.
Along the front range of the Rocky Mountains, in the Texas panhandle, and in the southern High Plains, thunderstorms frequently form as air near the ground flows "upslope" toward higher terrain. If other favorable conditions exist, these thunderstorms can produce tornadoes.
Tornadoes occasionally accompany tropical storms and hurricanes that move over land. Tornadoes are most common to the right and ahead of the path of the storm center as it comes onshore.
Tornadoes....Nature's Most Violent Storms