Research press release


Nature Climate Change

El Nino predictably drives fires through Asia to Americas



今回、Yang Chenたちの研究グループは、6回ずつのエルニーニョ現象とラニーニャ現象に対応する1997~2016年の人工衛星データを用いて火災による焼失面積と炭素排出量に関連する気候条件を調べ、エルニーニョ現象に関連する降水量と貯水量の減少によって汎熱帯林の火災による炭素排出量が増加し、ラニーニャ現象の場合の133%(平均)に相当することを明らかにした。また、Chenたちは、エルニーニョ現象が強まる時期に、8~10月に赤道アジアで最初に火災の発生件数が最も多くなり、この火災のピークが、翌年の1~4月には東南アジアと南米北部に移り、3~5月には中米、7~10月にはアマゾン川流域南部に移ることも明らかにした。


El Nino events significantly increase fire incidence and associated carbon emissions in pan-tropical forests, according to a paper published online this week in Nature Climate Change. The study finds that El Nino events reduce precipitation and water storage across pan-tropical forests, facilitating increased fire ignition and spread. These fires follow a predictable seasonal progression across tropical continents, which may help with fire-risk forecasting.

El Nino Southern Oscillation (ENSO) is a periodic variation in the coupled ocean-atmosphere system, with sea-surface temperature conditions - warm El Nino and cold La Nina - in the tropical eastern Pacific recurring every 2-7 years. ENSO has a pronounced influence on year-to-year variations in climate.

Yang Chen and colleagues identify the climatic conditions associated with burned area and fire emissions using satellite data from 1997-2016, covering six El Nino and six La Nina events. They find El-Nino-associated reductions in precipitation and water storage increase fire emissions in pan-tropical forests by 133% (on average) compared to La Nina events. The authors show that fires peak in equatorial Asia from August to October, while El Nino strengthens, before moving on to south-east Asia and northern South America from January to April of the following year, then Central America from March to May, and finally the southern Amazon from July to October.

The predictable cascade of fire described by the authors reveals an important lag in the Earth system response to ENSO, which could help improve seasonal fire-risk forecasts and explain some of the increased growth rate in atmospheric CO2 concentration during El Nino events.

doi: 10.1038/s41558-017-0014-8

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