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by Sarah Stevens

A new study published this week, The projected timing of climate departure from recent variability, predicts when the climates will change for cities across the world and it’s a lot sooner than you may think.

The study, led by Camilo Mora, developed a new metric, climate departure – the year when current climate change will result in brand new environments. Climate departure is the date when “the coldest year of the future will be warmer than the hottest year in the past.” So, according to the study, our recent summer heat wave would be only a warm winter spell…and this change is within our lifetimes.

The average date for global climate departure: 2047.

How is the climate departure determined?

Mora and his team combined predictions from the 39 models and created a timetable of global climate departures. They used temperatures from 1860 to 2005 as the historical bounds and determined the climate departure date when future temperatures exceeded the historical bounds.

Interestingly the study produced two predictions, one optimistic and one…not so optimistic. The first prediction is an immediate, significant reduction in greenhouse gases resulting in a later global climate departure, 2069. In the second prediction, “business as usual” as Mora refers to it, emissions increase regardless “of international climate agreements or strong domestic policies in the developed world.” It is the second prediction which provides the year 2047 for global climate departure however, even with dramatic reductions in emissions, the study only prolongs the climate departure by 22 years.

So which regions are at the highest risk?

The study found that tropical regions, not the poles, will experience climate departure first, approximately 15 years before the rest of the world – New Guinea in 2020, Jamaica in 2023, and Equatorial Guinea in 2024. Remember, climate departure refers to the break in historical temperatures, and the tropics have little variability, so the historical bounds are not as dramatic as those of higher latitudes. The earlier higher temperatures of the tropics pose significant environmental, economic, and population threats.

The tropics are home to approximately 80% of the world’s biodiversity. Tropical species are used to a very stable climate, unlike those living at the poles who are already adapted to large variability in the climate and as a result better suited to deal with climate change. (Mora) Economically, the region only generates around 20% of global economic output. As a result, these countries have the least ability to respond to the changes including effective conservation strategies. Furthermore, 40% of the world’s population lives in the tropics and will be affected by changes they may not be able to mitigate.

The study demonstrates that climate change is not a question of if, but a question of when. As they stand now, our cities are ill equipped to withstand dramatically increased temperatures as well as associated environmental impacts. We need to prepare out cities to be more resilient to a changing climate.

Read the full study published by Nature, The projected timing of climate departure from recent variability.


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Mora, Camilo; Frazier, Abby G.;  Longman, Ryan J.; Dacks, Rachel S.; Walton, Maya M.; Tong, Eric J.;  Sanchez, Joseph J.; Kaiser, Lauren R.; Stender, Yuko O.; Anderson, James M.; Ambrosino, Christine M.; Fernandez-Silva, Iria; Giuseffi, Louise M.; Giambelluca, Thomas W. “The projected timing of climate departure from recent variability.” Nature Publishing Group, a Division of Macmillan Publishers Limited. All Rights Reserved, 10 Oct. 2013.

Jervey, Ben. “New Study Predicts Year Your City’s Climate Will Change.” National Geographic. National Geographic Society, 09 Oct. 2013.