Why climate change hits poorest countries hardest

It's long been said that climate change will be felt earliest and most severely in the poor nations of the world that contributed the least to the problem. A recent study, along with illuminating data from a new World Bank Report, show how this is the case.

Why this matters: Solving climate change involves a fundamental mismatch between the countries that emit the most greenhouse gases, and those that stand to suffer the earliest and most from the problem. This is part of the reason of why addressing climate change has been so difficult to solve.

A new study, published in Geophysical Research Letters, provides a new way of understanding why a global average temperature increase above 1.5 degrees Celsius (2.7 degrees Fahrenheit) compared to preindustrial levels would be tough for poor, tropical nations to adapt to.

• The study uses the concept of a signal-to-noise ratio, factoring in the typical range of temperatures a region is accustomed to.
• The signal, according to the study, is the local change in average temperatures related to climate change.
• The noise is how variable the temperature normally is for that region.

Outside the tropics, places have greater year-to-year variability in temperatures, and are more adapted to a wide range of temperatures — from cold conditions to sizzling heat.

• But in the equatorial regions, where poorer nations tend to be located, society is accustomed to a higher average temperature that has little variability, or low amount of noise, associated with it. Therefore, it wouldn't take much warming to tip the climate outside of the accustomed range, making warming more noticeable.

What they're saying: Study co-author Andrew King, of the ARC Center of Excellence for Climate Extremes and the University of Melbourne in Australia, told Axios that the metric used in the study shows that even the most stringent temperature target under the Paris Climate Agreement would have a major impact in tropical regions by making intolerably hot temperatures far more common.

"The main result is that, in general, it will be the poorest people on the planet who experience the largest shift in their local climate if we go beyond the 1.5 degrees Celsius Paris limit. In the tropics the variability is lower, so the perceptibility of local climate change is higher there."

The bigger picture: Separate World Bank data released May 24 shows what would happen with heat extremes if there were about 2 degrees Celsius of global warming, and an emissions scenario more consistent with greater than 4 degrees Celsius of warming.

• In both scenarios, areas closest to the tropics — including some of the most populated places on the planet — would see a marked increase in days with a heat index exceeding 95 degrees Fahrenheit. The heat index combines temperature and humidity, and is used to measure how hot it feels to the human body.

Take note: The world has already warmed by more than 1-degree Celsius compared to the dawn of the industrial era.

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