Extreme weather events are expected to increase in both severity and frequency due to climate change, but which regions of the world will start to see these extremes emerging first? In order to answer this question, Luke Harrington from Victoria University of Wellington in New Zealand and his colleagues studied simulations of temperature change from 11 earth system models.

They compared historical simulations for the period 1901 to 2005 to predicted pathways up to the year 2100. Taking a one in one-thousand-day temperature extreme for the historic period they observed how the probability of exceeding such an event changed over time for different parts of the world.

The maps the team produced clearly show a belt around the tropics, representing a higher probability of extreme hot days due to climate change in this region. "Although absolute temperature increase is occurring faster in the Arctic, the temperature variability is also far greater in high latitude regions, so the signal of climate change emerging from this background noise of internal variability is happening more quickly in the tropics," said Harrington, whose findings are published in Environmental Research Letters (ERL).

To assess the impacts that these changes might have, Harrington and his colleagues aggregated the climate results with wealth distribution around the world. Most of the world's poorest people live at low latitudes. The team’s results clearly show that people in the world’s lowest socio-economic quintile are likely to be exposed to substantially more frequent daily temperature extremes at an earlier point in time than the wealthier population living at mid- and high- latitudes.

There are exceptions, like Singapore – a wealthy country at a tropical latitude – that will also experience the rapid emergence of extreme climate signals. But in general the regions that are likely to experience the earliest emergence of climate extremes are also the places where the poorest fifth of the world lives.

Those of us living at mid to high latitudes will indirectly feel the impact of this tropical climate change too. "Global populations are inexorably linked via trade and our study adds to the already large body of literature showing that agricultural output over the African continent will be severely impacted by worsening climate change, with likely negative implications for the prices of staple food crops globally," said Harrington.

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