Disasters like the violent storm that killed at least 50 people in southeastern Brazil are becoming more frequent due to climate change and unchecked construction in flood and landslide-prone areas, according to a renowned expert.

"The more time passes, the less likely it is to find survivors. But we always work with that in mind. There can always be air pockets under the rubble," emergency official Villas-Boas told news site G1. According to the Sao Paulo state government, dozens of people are still missing after the disaster.

In an interview for AFP, Francis Lacerda, a researcher at Brazil's IPA Climate Change Laboratory, discussed the causes of disasters like the one that struck the Sao Paulo state coast last weekend as well as what can be done to stop them.

Disasters, according to him, are a result of global warming, which has led to more extreme weather events across South America and the entire planet, not just in Brazil.

"There has actually been a decrease in the total amount of rain in Brazil in the southeast, central-west, north, and northeast in the past 30 or 40 years, even as these extreme episodes have increased," he said.

He explained that oceans are absorbing a significant portion of the heat contained in greenhouse gases, which is altering ocean currents. As a result, the atmosphere reacts to these extreme weather events and changes in how heat is distributed at Earth's poles and equator.

"So total precipitation has decreased, but the distribution has become more intense, with an entire year's worth of rain falling in a few hours in some cases. Yes, although mountainous areas are at higher risk."

Read next: 36 dead in Brazil's deadly Sao Paolo floods, landslides

He illustrates how the mountain range and the arrival of a cold front with strong coastal winds intensified the phenomenon. However, coastal regions without mountains can also experience that kind of rain.

Lacerda added that "it was a tragedy foretold. A day before the storm, meteorological models started indicating a high probability of a phenomenon like this. It would have been possible to get enough information to emergency officials to evacuate these areas and save lives."

The expert explained that real-estate speculation has basically pushed poor people on the urban periphery into these high-risk areas. "It's not enough to just say, 'Get those people out of there.' We need to fundamentally reexamine our cities with a view to reformulating urban public policies."

Read next: Deforestation in Brazil's Amazon falls in Lula's 1st month in office