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Business News/ News / World/  How climate change affects cities’ daily temperatures, mapped

How climate change affects cities’ daily temperatures, mapped

A new online tool shows the influence of global warming on today’s highs and lows in more than 1,000 global cities

Climate Shift Index, a new online mapping tool, will help in knowing how climate change affects cities' daily temperature (Reuters)Premium
Climate Shift Index, a new online mapping tool, will help in knowing how climate change affects cities' daily temperature (Reuters)

 The world is now 1.1C hotter on average than it was in 1850, before widespread industrialization. But this number can obscure the lived experience of climate change — how we question whether this year was hotter than the last, or how some regions of the world are warming faster than others. 

A new online mapping tool called the Climate Shift Index (CSI), developed by the US-based research and communications group Climate Central, illustrates how daily average temperatures in more than 1,000 cities around the world are made more or less likely by global warming.

In June, Climate Central made it possible to map nearly in real time the effect of climate change on thermostats across the US. On one day in July, for instance, areas from California to Florida, shaded deep maroon, showed temperatures made drastically more likely by climate change. 

Now, with the launch of a global version of the index, people in Jakarta, Addis Ababa and Shanghai can also track how much human-induced climate change is making their days (and nights) hotter or oddly mild in colder months. 

“In some ways, what we’re doing is keeping score," said Andrew Pershing, director of climate science at Climate Central. “You can think about what has your experience with climate change been, filtered through the lens of weather." 

Pershing and his team use data from NOAA’s Global Forecast System to compare climate models with and without human-caused climate change, presenting the probability of the difference using a scale from -5 to 5, with 0 denoting no climate effect. For instance, if Miami gets a 5 on a given day, the temperature there that day is at least five times more likely because of climate change. Or if Kathmandu is swathed in gray at -2, the temperature there is two times less likely to occur at that date as a result of global warming. 

The challenge of making climate change local is that weather still fluctuates day to day. When the weather is most variable, as in autumn in the US, temperature changes may be masked, resulting in a relatively quiet map. By contrast, during heat waves, the story of climate change becomes much more apparent, as it was in Europe and China this summer. 

If you were to zoom over to Mauritania, Morocco or Saudi Arabia on the CSI map, you’d see climate fingerprints today. Just this week, climate change continued to influence temperatures in the equatorial region, particularly small island states and coastal regions, which border the warming ocean. 

Over the past year, from October 1, 2021 to September 30, 2022, climate change shifted temperatures to the greatest extent in the Malay Archipelago (from Malaysia to Papua New Guinea), Brazil, Mexico, the Arabian Peninsula and the Horn of Africa, according to a Climate Central analysis. The cities of Apia, Samoa and Ngerulmud, Palau scored highest overall, each with 90% of their days unusually out of sync with what their temperatures would have been before the climate crisis. 

The researchers also adjusted their analysis to represent population centers, multiplying the number of days with relative climate impacts by the number of people in a place. Whereas small island states appeared most affected overall — a key finding for both climate adaptation and conservation — African cities, particularly Lagos, Nairobi, Dar es Salaam and Mogadishu, jumped to the fore for greatest total human exposure to rising local temperatures. 

Victoria Keener, senior research fellow at the nonprofit East-West Center in Honolulu, said that Climate Central’s findings are consistent with those of the 2021 Pacific Climate Change Monitor, an international collaboration that analyzed observed data from Pacific islands. Over the past decade, heat waves have increased in length across the Pacific, and states including the Marshall Islands have seen a significant rise in the number of hot days and hot nights. 

Particularly in the context of the approaching COP27 talks, where “loss and damage" is expected to be a focus, coalitions of island nations could use the map to argue in broad strokes the toll of climate change and the need for greater climate finance from rich nations. 

“I see this as another tool to quantify how much they didn’t contribute [to climate change] and are now experiencing it at the greatest levels," said Keener. “It’s the same story that we see again." 

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This story has been published from a wire agency feed without modifications to the text.

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Published: 27 Oct 2022, 04:32 PM IST
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