Upwards of 5 billion people in the tropics will soon find temperature and other weather conditions falling outside anything experienced in modern record-keeping, according to a groundbreaking study published Wednesday.
The study, published in the journal Nature by a team of University of Hawaii researchers led by professor Camilo Mora, is the first to map the timing of "climate departures" – when a particular region's climate conditions escape the bounds recorded over the past 140-odd years by modern instruments.
The map at right shows the year of anticipated climate departure for cities around the world, including New York City and Washington, D.C., at 2047; Orlando, Fla., at 2046; and San Francisco at 2049.
Among the team's surprising findings: The tropics will depart first, even though all climate models and data show the Arctic is warming fastest. And the transformation, underway now, will happen very quickly, with broad ramifications for wildlife and biodiversity in some iconic wild landscapes.
"We didn't anticipate that these timings were going to be that early," Mora said in an interview. "The tropics are going to be the most vulnerable."
The Mora lab's analysis shows that 1 billion people will find their local climate outside historic norms starting as early as 2020, even if stringent emissions curbs are in place. Without curbs, some 5.5 billion people worldwide will find their homes outside climate norms within 50 years.
Plot those findings against economic data, Mora said, and the situation grows dire: The regions facing the impacts first – southeast Asia, much of sub-Sahara Africa – have the least economic ability to respond.
Stuart Pimm, professor of conservation ecology at Duke University, called the findings astonishing and turned to Shakespeare's famous line in The Tempest for perspective: "What's past is no longer prologue," he said. "We are outside of our experience."
The results are counterintuitive. While the globe has warmed an average of 0.9 degrees Celsius (1.4ºF) over the past century, the warming has not been even: The Arctic has warmed twice as much over that period, scientists say, and melting ice and polar bears have become the face of climate impacts.
But the Arctic experiences wild temperature swings. Species – and humans – there are adapted to a broader climate band. Thus, said Mora, the region needs a bigger temperature swing to depart its climate history: Anchorage, for instance, won't escape today's climate norm until closer the 2070s, according to the Mora Lab's data.
Life in the tropics, however, is accustomed to a far narrower band, Mora said. So while the temperature change may be smaller than what's seen in the Arctic, the impact is keener: Manokwari, a city of 130,000 in West Papua, Indonesia, will be the first in the globe to depart its climate, heading into uncharted waters for good by 2020, Mora's data show.
Read the full report at DailyClimate.org, a foundation-funded news service that covers climate change edited by Douglas Fischer. Republished with permission.
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