Asia just had a deadly heat wave, and scientists say it could happen again. Here's what's making it much more likely.

Hundreds of people died across Asia in recent weeks as the region sweltered under blistering temperatures. And a new study determined a leading factor in how it all happened. 

Last month, many areas in India saw temperatures well above triple digits. The country's meteorological service says that heat waves are not uncommon between March and June, with May being the "peak month" for the extreme weather event. In Bhagdora, India, last month, temperatures hit nearly 115 degrees Fahrenheit as the India Meteorological Department issued a red alert warning, meaning that severe heat was expected to persist for more than two days and there was a very high likelihood for heat-related illnesses. 

Elsewhere in the country, it was so hot that schools were canceled, an issue that people also faced in the Philippines. People in Thailand were also asked by officials to stay indoors when possible to avoid the heat, as dozens of people had already died from heat-related illnesses. According to the Associated Press, the April heat killed at least 28 people in Bangladesh, five in India and three in Gaza. 

And according to the organization World Weather Attribution, it all comes down to two words – climate change. 

"The heat wave exacerbated already precarious conditions faced by internally displaced people, migrants and those in refugee camps and conflict zones across West Asia," a new study from the organization said. "... The extreme heat has forced thousands of schools to close down in South and Southeast Asia." 

Researchers said that while the kind of heat experienced during this time "is not very rare," it's only being amplified by climate change, which is fueled by global warming largely caused by the burning of fossil fuels. 

West Asia is anticipated to get an extreme heat event once a decade, and in the Philippines, that likelihood is even less, about once every 20 years when El Niño isn't at play. In South Asia at large, extreme heat is not common. 

"An extremely warm April such as this one is a somewhat rarer event, with a 3% probability of happening in a given year – or once every 30 years," researchers said, adding that observations and data models show that human-caused climate change creates a "strong increase in likelihood and intensity." 

"In the Philippines, the change in likelihood is so large that the event would have been impossible without human-caused climate change," they said. "In West Asia, climate change increased the probability of the event by about a factor of 5."

The average April temperatures in South Asia, which the group has studied twice in the last two years from other extreme events, "are now about 45 times more likely and 0.85 degrees Celsius hotter," they found. 

"Sounds like a broken record – yes! But heat is still underreported, underrecorded and extremely deadly," Friederike Otto, who is part of the World Weather Attribution study, said on social media. "The world is not prepared for today's climate change, let alone the future." 

Extreme heat is "becoming the silent killer," Ko Barrett, deputy secretary-general of the World Meteorological Organization, said in April. 

"Heat-related mortality is widely under-reported and so the true scale of premature deaths and economic costs – in terms of reduced labor productivity, agricultural losses, and stress on the power grid - is not accurately reflected in the statistics," she said. 

The report from the World Weather Attribution came a day ahead of another report from the WMO that found this April was the warmest one on record and the 11th consecutive month of record temperature worldwide. 

The average surface air temperature last month was 15.03 degrees Celsius, about 59 degrees Fahrenheit, more than 1.5 degrees Celsius warmer than pre-industrial times. Scientists have warned that if the planet experiences persistent temperatures at that 1.5 threshold, it could cause significant impacts on weather events leading to global issues surrounding food and water availability, migration and infrastructure. 

"The record temperatures were accompanied by high-impact weather events — including intense heat in many parts of Asia," the WMO said. "The heat also had a large impact on agriculture, causing crop damage and reduced yields, as well as on education, with holidays having to be extended and schools closed in several countries, affecting millions of students." 

It will take years of this continued breaching of 1.5 degrees above preindustrial levels for the planet to officially mean humans have failed to achieve the goals of the Paris Agreement and launched the world into a more disastrous climate era. However, 11 months of record heat – and potentially beyond – indicates "early signs of getting perilously close to exceeding the long-term limit," the United Nations says. 

"Every fraction of a degree of warming matters. With every additional increment of global warming, changes in extremes and risks become larger," the international agency says. "... We need to bend the global emissions curve — and the production and consumption of coal, oil, and gas - downwards, starting now. A wide range of solutions exist." 

Arshad R. Zargar contributed to this report.

In:
• India
• Thailand
• Climate Change
• Heat
• Philippines
• Heat Wave

Li Cohen

Li Cohen is a social media producer and trending content writer for CBS News.