Published on behalf of the Victoria University of Wellington.
Research by Luke Harrington and Professor David Frame from the New Zealand Climate Change Research Institute shows heat extremes are quickly becoming more frequent for countries nearer the equator—mainly poorer nations.
“A much greater fraction of the poorest parts of the world live in tropical latitudes, while most of the world’s most developed countries are in mid-latitude climates, like New Zealand,” says Professor Frame.
“Low-latitude regions have less variability in day-to-day temperatures when compared with mid-latitude climates, which means the ‘signal’ of climate change emerges quite quickly, and because of this, the frequency of extremely hot days increases rapidly too.
“This means because of where they live, many of the poorest people of the world are experiencing much greater increases in the number of very hot days when compared with the wealthiest countries of the world”.
The study, just published in scientific journal Environmental Research Letters, used climate models to simulate cumulative carbon dioxide (CO2) emissions and changes to extreme daily temperatures over the 20th and 21st century. An extremely hot day was defined, relative to local climate, as occurring 0.1 percent of the time in the pre-industrial climate.
The rapid increases in hot day frequency look likely to continue into the future, says Mr Harrington, a PhD student at Victoria University.
“Even if heat extremes were becoming more frequent for all countries at the same rate with climate change, we know the wealthiest countries will be able to cope with the impacts more easily than poorer nations.
“What our research shows is that heat extremes do not increase evenly everywhere, but are becoming much more frequent more quickly for countries nearer the equator—these are mainly poorer nations. Importantly, this disparity in exposure between the global rich and poor will only continue to get worse as we emit more CO2 into the atmosphere.”
The paper is appearing as part of a special edition of Environmental Research Letters on cumulative emissions of CO2, and is the first paper to explore links between times of emergence of extremely hot days with cumulative emissions of CO2.
The two Victoria scientists worked in collaboration with researchers from the Universities of East Anglia and Reading, the Institute for Atmospheric and Climate Science at ETH Zürich University, and the Met Office Hadley Centre in the United Kingdom, and the research is in part supported by the Deep South National Science Challenge.