I wrote the other day about timelines, and the importance of having a more vigorous discussion of home much time we actually have to zero-out emissions and ruggedize for climate disruption.

The answer is: Not much time at all. In a meta-study described in the current issue of nature, researchers compared all major climate models and found that under business-as-usual scenarios, life-altering climate impacts will unfold over the next 35 years:

“Within 35 years, even the lowest monthly dips in temperatures will be hotter than we’ve experienced in the past 150 years, according to a new and massive analysis of all climate models. The tropics will be the first to exceed the limits of historical extremes and experience an unabated heat wave that threatens biodiversity and heavily populated countries with the fewest resources to adapt.

“Ecological and societal disruptions by modern climate change are critically determined by the time frame over which climates shift. Camilo Mora and colleagues in the College of Social Sciences’ Department of Geography at the University of Hawai‘i at Mānoa have developed one such time frame. The study, titled “The projected timing of climate departure from recent variability,” will be published in the October 10, 2013 issue of Nature and provides an index of the year when the mean climate of any given location on Earth will shift continuously outside the most extreme records experienced in the past 150 years.

“The new index shows a surprising result. Areas in the tropics are projected to experience unprecedented climates first – within the next decade. Under a business-as-usual scenario, the index shows the average location on Earth will experience a radically different climate by 2047. Under an alternate scenario with greenhouse gas emissions stabilization, the global mean climate departure will be 2069.

“The results shocked us. Regardless of the scenario, changes will be coming soon,” said lead author Camilo Mora. “Within my generation, whatever climate we were used to will be a thing of the past.” …

The scientists then took projections for the next 100 years to identify the year in which the future temperature at any given location on Earth will shift completely outside the limits of historical precedents, defining that year as the year of climate departure.

This last concept, of “climate departure,” is new to me, and disturbingly apt. (The map at the top of the post shows when the climate major cities are likely to “shift completely outside the limits of historical precedents,” according to the study. Note that both Lagos and Jakarta hit climate departure in 2029… essentially 15 years from now. Some of the fastest-growing most-strained emerging megacities will be some of the first hit.)

The take-away here, to me, is that serious climate chaos is upon us. Through bold and rapid action, we can reduce the degree and suddenness of that chaos, but unprecedented climate conditions are something people alive today will have to respond to.

Thanks to Bill McKibben for suggesting I check out this study.