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Author: Nicky Phillips
Source: The Age
Date: 10 October, 2013

Sydney endured its hottest September on record this year. Thursday may be our hottest October day. But when do we stop talking about breaking records and admit we’ve got a radically different climate?

In Sydney, a new study suggests that time will come in 2038.

Climate scientists have created an index of the year when the average climate of any given region on Earth will likely push outside the extreme records of the past 150 years, should greenhouse gas emissions continue unabated.

This means that regardless of the natural variation in the climate, the lowest monthly dips in temperature will still be hotter than the planet has experienced in the past century-and-a-half.

Research leader Camilo Mora, from the University of Hawaii, said this study showed change was already upon us. “Within my generation, whatever climate we were used to will be a thing of the past.”

The index, published in Nature, found if emissions continued as usual, countries in the tropics would be the first to enter new climate territory, about 2038. Parts of Indonesia would face such conditions by the end of the decade, while the average global temperature would depart from the climate variability of the past 150 years by 2047.

If emissions were stabilised, the shift could be delayed until 2069.

The index projections, created from 39 global climate models from 12 countries, used the minimum and maximum temperatures between 1850 and 2005 to define the boundaries of historical variations in climate at any given place.

From climate projections for the next 100 years they calculated the year in which the average climate for a location would shift outside the extremes of the past 150 years.

The shifts will particularly affect food and water supply, the spread of diseases and the incidence of heat stress, the researchers said.

Study co-author Ryan Longman said many of the first countries to feel the effects had the least capacity to respond – and were the countries least responsible for climate change in the first place.

Australian climate scientist Sarah Perkins, from the ARC Centre of Excellence for Climate System Science, said the study’s results were in line with the latest global projections.

However, she expressed reservations about the study’s time frames, saying climate models were not designed to provide projections for such precise times and locations.

Read article at The Age