Top Story: October 16, 2013

The When of Climate Change

climate, variability, change, departure, mora, hawaii, tropics, warming, global, 2047

By Molly Michelson

Climate patterns vary from year to year and place to place, but a recent study pinpoints when temperatures will depart from the variability we’ve witnessed over the past 150 years: 2047.

In 2047, even the coldest months and years we witness will be warmer than the hottest months and years of the past. But note that the 2047 timeframe represents a global average of surface air temperatures; the tropics will feel this climate departure even sooner.

Camilo Mora and his colleagues at the University of Hawaii, Manoa, developed an index of this climate departure by undertaking a massive analysis of 39 different climate models. They first made calculations of several climate factors (including near surface air temperatures, evaporation, precipitation, plus ocean surface temperature and pH) for the years 1860 to 2005. 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.

Under a business-as-usual scenario, the index shows the average location on Earth will experience a radically different climate by 2047. Areas in the tropics are projected to experience unprecedented climates first—within the next decade. Under an alternate scenario with greenhouse gas emissions stabilization, the global mean climate departure will not occur until 2069.

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

Previous studies have focused on more dramatic changes in absolute temperature in Earth’s polar regions. But Mora and his colleagues found that the projected rapid changes in the tropics will have a greater overarching effect on global biodiversity and human populations. The tropics hold the world’s greatest diversity of marine and terrestrial species and are unaccustomed to climate variability. This means that even relatively small changes in these hotspots greatly affect life.

In addition, human life is vulnerable in these developing, sometimes quite poor regions. “Our results suggest that countries first impacted by unprecedented climates are the ones with the least capacity to respond,” says co-author Ryan Longman. “Ironically, these are the countries that are least responsible for climate change in the first place.”

The study suggests that any progress to slow ongoing climate change will require a larger commitment from developed countries to reduce emissions, and also more extensive funding of social and conservation programs in developing countries to minimize climate change impacts. The longer we wait, the more difficult it will be.

The team has created an interactive map to see climate departure by region. “We hope that with this map people can see and understand the progression of climate change in time where they live, hopefully connecting people more closely to the issue and increasing awareness about the urgency to act,” says co-author Abby Frazier.

“Scientists have repeatedly warned about climate change and its likely effects on biodiversity and people,” concludes Mora. “Our study shows that such changes are already upon us. These results should not be reason to give up. Rather, they should encourage us to reduce emissions and slow the rate of climate change. This can buy time for species, ecosystems, and ourselves to adapt to the coming changes.”

The study was published last week in Nature.

Image courtesy of the Mora Lab, University of Hawaii

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