By Matt McGrath.
The environment correspondent.
A new study says that climate change will make millions more vulnerable to devastating tropical storms.
The hurricanes are mainly confined to the tropical regions north and south of the equator.
Researchers say that rising temperatures will allow these weather events to form.
New York, Beijing, Boston and Tokyo are included in this area.
The study was published in a journal.
The scientists involved say that by the end of this century, they will likely see a wide range of cyclones.
The small scale of damage caused by the storm in Portugal made little news.
This was a big event for scientists.
"We hadn't seen this before," said Dr Joshua Studholme, a physicist from Yale University.
The right conditions for a tropical cyclone to form occurred when a traditional mid-latitude storm decayed, and that hadn't happened before in Portugal.
The image caption is.
Three hurricanes formed off the US coast.
Dr Studholme is the lead author of a new study that says a warming climate will cause more of these storms to form in the mid-latitudes, where most of the world's population lives.
The flow of the jet streams will be affected by the decline in the temperature between the equator and the polar regions.
These high-altitude rivers of air act as a kind of border guard for hurricanes, keeping them closer to the equator.
"As the climate warms, the jet stream activity that happens in the middle latitude will weaken and in extreme cases split, allowing this sort of cyclone formation to occur."
Recent research suggests that the connection between the impact of human climate change and hurricanes is becoming clearer.
The image caption is.
The wall of the eye of a storm.
The authors said they had high confidence that the evidence of human influence has strengthened.
Increasing global warming will increase the proportion of intense tropical cyclones, average peak tropical cyclone wind speeds, and peak wind speeds of the most intense tropical cyclones.
Multiple strands of evidence were used to show that tropical storms are likely to occur over a wider range than previously thought.
"We've made explicit the links between the physics going on within storms and the dynamics of the atmosphere at the planetary scale," said Dr Studholme.
This is a difficult problem because the physics isn't well simulation in numerical models.
The expansion of these storms poses a significant danger to the world when other impacts of warming come into play.
"Tropical cyclones in the mid-latitude band could experience other changes such as slower motion and heavier rain," said Dr Gan Zhang, who was not involved in the new paper.
The image is from the same source.
The image caption is.
The US was hit by Hurricane Ida this summer.
Potential societal impacts might be compounded by these tropical cyclone changes.
Even with moderate levels of warming, the risk from tropical storms could still increase even though the sensitivity is high.
The authors argue that dramatic reductions in carbon emissions over the next decade could alter the outcome, and that this course is not set in stone.
The control over this is the temperature difference between the tropics and the poles.
The difference between a high emission scenario and a low emission scenario will be dramatic by the end of this century. That can be very important in terms of how these hurricanes play out.
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