From severe storms in the spring to record heat in the summer, each season brings with it a host of extreme weather events that are becoming more frequent and intense as a result of climate change. By understanding these climate connections, reporters can make crucial links between extreme weather events and human-caused climate change to their audiences.
This guide summarizes what emerging climate research says about spring severe weather, including tornadoes, hail, and flooding. Included in this guide are examples of vetted language produced in conjunction with Climate Central, a scientific organization that studies and reports on climate change.
Hail
Hailstorms are by far the most costly hazard associated with severe thunderstorms, causing $10 billion of insured losses annually in the US, more than the costs caused by tornadoes, lightning-caused fires, and severe wind combined. In the past decade, there have been several instances of a single hailstorm causing over a billion dollars in damage in Texas, Colorado, Minnesota, and in Alberta, Canada.
Research has found that large, damaging hail will become more common as the planet warms. Scientists say that climate change supercharges storms as warmer temperatures provide more energy to create stronger updrafts inside a storm which in turn support heavier, larger hail. A recent study found that the largest hailstones, the size of a golf ball or larger, will increase in frequency up to 75% with current climate projections. The same study found that smaller, less damaging hail, will become less common as warmer temperatures allow them to fully melt before impact.
Language you can use to make the climate connection: Hailstorms already inflict billions of dollars in damage each year, and this threat is growing as human-caused climate change makes large, destructive hail more likely.
Tornadoes
Unlike temperature or precipitation trends, climate change’s influence on tornadic activity is difficult to pin down. Tornadoes are notoriously complex, with researchers still determining how best to differentiate the potential influence of climate change on a tornado compared to the natural variability in our weather. Current climate models often struggle to adequately capture these intense, but short-lived and small weather events compared to larger, longer lasting phenomena, such as tropical cyclones.
While the overall number of tornadoes each year hasn’t changed much since the 1970s, research shows that tornado outbreaks, or days with multiple tornadoes, are becoming more frequent as our climate warms. Research also suggests that the potential for nocturnal tornadoes may rise with future climate warming. Nighttime tornadoes, occurring between sunset and sunrise, are almost twice as deadly as daytime tornadoes as more people are asleep, making it more difficult to hear warnings and seek shelter.
In the US, which experiences more tornadoes than anywhere else in the world due to its unique geography, observational trends show that tornado outbreaks have been migrating eastwards, from the historical “tornado alley” in Texas and Oklahoma towards Tennessee and Alabama over the past 30 years. Not only are we seeing a change in where tornadoes occur, but also when. Weather conditions favorable to supercells, the intense, rotating thunderstorms which spawn tornadoes, are becoming more common outside of the typical “severe weather season” in early spring, with more off-season tornado activity in the fall and winter.
Language you can use to make the climate connection: Supercell and tornado conditions are shifting to new locations and expanding beyond the traditional season. As the climate warms, more supercells are expected in months like February, March, and early April by the end of the century.
Flooding
As one of the deadliest natural disasters, second only to extreme heat, floods destroy communities, disrupt livelihoods, and increase the risk of pest and waterborne illnesses. The climate connection here is much simpler, and is grounded in physics: a warmer atmosphere can hold more moisture, fueling heavier downpours.
While flooding is influenced by other non-meteorological factors such as land-use and flood defense strategies, data shows that heavy rainfall has become more frequent and intense across most of the world since the 1950s. Research shows that with continued warming, precipitation extremes are likely to increase across the world, even in regions with decreasing average precipitation.
Language you can use to make the climate connection: As our climate warms, the most extreme rainfall events have become more frequent and intense across much of the world.