Amazon Under Threat From Cleaner Air
May 12, 2008
The Amazon rainforest, so crucial to the Earth's climate system, is coming
under threat from cleaner air say prominent UK and Brazilian climate
scientists in the leading scientific journal Nature.
The new study identifies a link between reducing sulphur dioxide emissions
from burning coal and increasing sea surface temperatures in the tropical
north Atlantic, resulting in a heightened risk of drought in the Amazon
rainforest.
The Amazon rainforest contains about one tenth of the total carbon stored in
land ecosystems and recycles a large fraction of the rainfall that falls
upon it. So any major change to its vegetation, brought about by events like
deforestation or drought, has an impact on the global climate system.
A team from the University of Exeter, Centre for Ecology and Hydrology, Met
Office Hadley Centre and Brazilian National Institute for Space Studies used
the Met Office Hadley Centre climate-carbon model to simulate the impacts of
twenty-first century climate change on the Amazon rainforest. They compared
the model to data from the 2005 drought, which caused widespread devastation
across the Amazon basin. The researchers estimate that by 2025 a drought on
this scale could happen every other year and by 2060 a drought could occur
in nine out of every ten years.
Co-author Dr Matthew Collins of the Met Office Hadley Centre puts this into
context: "The rainforest is under many pressures. Direct deforestation is
the most obvious immediate threat, but climate change is also a big issue
for Amazonia. We have to deal with both if we want to safeguard the forest."
Co-Author Dr Carlos Nobre of the Brazilian Institute for Space Research
adds: "Global warming, deforestation and increased forest fires are all
acting in synergy to reduce the resilience of the Amazonian forests".
Sulphate aerosol particles arising from the burning of coal in power
stations in the 1970s and 1980s have partially reduced global warming by
reflecting sunlight and making clouds brighter. This pollution has been
predominantly in the northern hemisphere and has acted to limit warming in
the tropical north Atlantic, keeping the Amazon wetter than it would
otherwise be. Chris Huntingford of CEH, another of the co-authors, explains:
"Reduced sulphur emissions in North America and Europe will see tropical
rain-bands move northwards as the north Atlantic warms, resulting in a sharp
increase in the risk of Amazonian drought".
Lead author Professor Peter Cox of the University of Exeter sums-up the
consequences of the study: "These findings are another reminder of the
complex nature of environmental change. To improve air quality and safeguard
public health, we must continue to reduce aerosol pollution, but our study
suggests that this needs to be accompanied by urgent reductions in carbon
dioxide emissions to minimize the risk of Amazon forest dieback."
SOURCE: University of Exeter
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