The papal encyclical set to be released Thursday will highlight the threats posed by climate change on the world's poorest, most impoverished citizens — a population scientists have long warned will be disproportionately affected by global warming.
Whether marginalized groups in developed countries or the more general population in the developing world, "the basic issue is that the poor don't have resources to be resilient to changes," said climatologist Gavin Schmidt of NASA.
There simply isn't enough money available to improve how such groups deal with everyday weather, let alone the drastic changes global warming can bring, he added.
"People, governments and corporations in lower-income countries are increasingly impacted by droughts, superstorms, civil conflicts and other disasters caused by climate change," according to Joyce Coffee of the Notre Dame Global Adaptation Index, which ranks the climate adaptation performance for the world's countries.
Some of the top climate threats include sea-level rise, more powerful hurricanes, shrinking water resources, decrease in agricultural productivity and increased extremes of wet and dry, both from devastating floods to harsher droughts, according to climatologist Michael Mann of Penn State.
A look at four of the top impacts of climate change worldwide and what regions will be most affected by each:
"The number one concern for the poor with respect to climate change has to be drought, both now and in the future," said meteorologist Jeff Masters of the Weather Underground.
Recent devastating droughts in the Mediterranean region — specifically in Syria from 2006 to 11 — and another one in Somalia in 2010-11 have both been linked to man-made climate change, according to Masters.
Areas most at risk: Africa, Pakistan, Brazil, China, and the Central America/Caribbean region, according to Masters.
Many poor populations live in river flood plains or along low-lying areas near the coast, making flooding a huge concern worldwide, both from heavy rain and storm surge.
Climate change is likely to make heavy precipitation events even more common, according to the Intergovernmental Panel on Climate Change. One flooding incident linked to climate change is the catastrophic monsoon in 2013, which killed thousands in India, Masters said.
"Climate change ultimately reveals and amplifies already existing income, social and other gaps," said Marshall Shepherd of the University of Georgia. "If you look at Hurricane Katrina, many folks of all demographics and incomes were affected, but the poorest and marginalized were most vulnerable and least able to adapt afterwards."
Areas most at risk: Bangladesh, China, Vietnam, Indonesia, India, Thailand, the Philippines, Myanmar and Malaysia, according to Masters.
Rising temperatures will also impact the food and water supply. "Temperatures will be moving outside the band of what has been experienced in recent centuries and it's not clear what impact that will have on food production, ecosystems and populations," Schmidt said.
Crop yields in the tropics, home to hundreds of millions of subsistence farmers, are likely to see negative impacts due to climate change, according to meteorologist Robert Henson in his book The Thinking Person's Guide to Climate Change.
There will be a "sharp decrease in agricultural productivity in warm (tropical) regions," Mann said.
Areas most at risk: The tropics, particularly the nations of Djibouti, Sudan, Somalia, Yemen and Eritrea, according to Notre Dame's Global Adaptation Index.
One of the clearest signals of man-made climate change is more frequent and intense heat around the world. Last year was the warmest ever recorded, according to NOAA and NASA, and 2015 is on pace to break that record.