Tropical regions will experience the greatest shifts in climate this century with some equatorial areas experiencing unprecedented changes as early as the next few decades, a study has found.
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Scientists discovered that the tropics, which are home to the highest densities of wildlife as well as some of the most vulnerable human populations on the planet, will be hit hardest and earliest by climate extremes.
A “meta-analysis” of future climate predictions culled from 39 global computer models used in climate research found that tropical regions are expected to cross the threshold into unprecedented climate change significantly earlier than other areas of the world. If industrial emissions of greenhouse gases remain unchanged in a “business-as-usual” scenario then some tropical regions, such as Jamaica and Indonesia, could see a shift into new climate territory as early as the next decade, the scientists warned.
“The results shocked us. Regardless of the scenario, changes will be coming sooner. Within my generation, whatever climate we were used to will be a thing of the past,” said Camilo Mora of the University of Hawaii, the lead author of the study published in the journal Nature. “On average, the tropics will experience unprecedented climate [change] 16 years earlier than the rest of the world, starting as early as 2020,” Dr Mora said.
Although the Arctic region has seen some of the greatest changes in climate, with the region warming significantly faster than the global average, it is in the tropics where the changes will hit hardest because it is here that wildlife and human populations are accustomed to relatively constant natural variations in the climate, the researchers said.
“Scientists have repeatedly warned about climate change and its likely effects on biodiversity and people. Our study shows that such changes are already upon us,” Dr Mora said. “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,” he said.
The study analysed minimum and maximum temperature ranges from 1860 to 2005 – the period of accurate instrumental readings – to provide a baseline of recent climate extremes. It then looked at computer climate projections into the next 100 years to see where future temperatures are likely to go for any given location on Earth.
The scientists wanted to find the date when a point on the Earth is likely to slip into a new climate state that it had not experienced during this historical period. For instance they wanted to see when, for each place, the lowest monthly-average temperatures will be hotter than anything experienced over the past 150 years.
For the business-as-usual scenario of greenhouse gas emissions, London is expected to slip into this unprecedented climate state by around 2056, whereas Nairobi will reach it in 2036, Mumbai in 2034 and Manokwari in Indonesia in 2020 – give or take five years in each location.
The researchers said that tropical species, which have evolved for millions of years within a fairly narrow range of climate extremes, will find it hard to survive. They will either have to move, adapt or go extinct, they said.
“This work demonstrates that we are pushing the ecosystems of the world out of the environment in which they evolved into wholly new conditions that they may not be able to cope with,” said Ken Caldeira of the Carnegie Institution for Science in Stanford, California.
“Extinctions are likely to result. Some ecosystems may be able to adapt, but for others, such as coral reefs, complete loss of not only individual species but their entire integrity is likely,” Dr Caldeira said.