New Study Reveals Timeframe for Climate Change

The seesaw variability of global temperatures often engenders debate over how seriously we should take climate change.

But 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.

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” 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.

So, tropical species are unaccustomed to climate variability and are therefore more vulnerable to relatively small changes. The tropics hold the world’s greatest diversity of marine and terrestrial species and will experience unprecedented climates some 10 years earlier than anywhere else on Earth. Rapid change will tamper with the functioning of Earth’s biological systems, forcing species to either move in an attempt to track suitable climates, stay and try to adapt to the new climate, or go extinct.

These changes will affect our social systems as well.  In predominately developing countries, over one billion people under an optimistic scenario, and five billion under a business-as-usual-scenario, live in areas that will experience extreme climates before 2050. This raises concerns for changes in the supply of food and water, human health, wider spread of infectious diseases, heat stress, conflicts, and challenges to economies.

While the study describes global averages, the authors have visualized their data on an interactive map displaying when climate will exceed historical precedents for locations around the world. The index used the minimum and maximum temperatures from 1860-2005 to define the bounds of historical climate variability at any given location.

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.

The data came from 39 Earth System Models developed independently by 21 climate centers in 12 different countries.  The models have been effective at reproducing current climate conditions and varied in their projected departure times by no more than five years.

 “Scientists have repeatedly warned about climate change and its likely effects on biodiversity and people,” said 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.”