research HIGHLIGHTS

research HIGHLIGHTS

Biodiversity and ecology

Shrooms shrivel

Global Change Biology

doi:10.1111/j.1365-2486.2008.01716.x (2008)

Mushrooms growing in northern forests

may provide a helping hand in combating

climate change. As soils heat up, the fungi that

feast on dead plant material can wither away

and emit less carbon dioxide, new research

suggests. Such changes in northern forests and

tundra, which store an estimated 30 per cent

of terrestrial carbon, could substantially alter

atmospheric levels of the greenhouse gas.

In a spruce forest near Fairbanks, Alaska,

Steven Allison and Kathleen Treseder of the

University of California, Irvine, measured a

literal greenhouse effect, enclosing plots of soil

in plastic structures that trapped heat but let

in rain. The greenhouse plots averaged 0.5 °C

warmer than controls, and over three years

lost 22 per cent of their moisture — and more

than half of their bacteria and fungi, according

to DNA analyses. The fungal group most

affected includes mushroom species thought

to produce high carbon emissions. The release

of carbon dioxide from the covered plots fell

by up to 50 per cent as soils dried at the end of

each growing season.

The authors say the results were

unexpected, and suggest they are specific

to the type of environment they studied: a

well-drained forest with no permafrost, such

that the soil dries easily.

Anna Barnett

Atmospheric science

Assessing ethane

J. Geophys. Res. 113, D21306 (2008)

Methane emissions from energy production

in the United States could be as much as 50

to 100 per cent higher than current estimates

suggest. A potent greenhouse gas, methane

is generated from the production of fossil

fuels — mostly natural gas, as well as from

biomass burning, agriculture and as from

natural sources such as wetlands.

Ethane, released during the production

of fossil fuels, is strongly correlated with

methane in the atmosphere and as such can be

used as an effective tracer of the greenhouse

gas. Xiao Yaping, of Harvard University,

and colleagues used a chemical transport

model to evaluate a global inventory of

ethane, verifying the model simulations with

observations taken from surface sites and

aircraft missions worldwide. They derived

a global ethane inventory of 13 million tons

per year. The majority of emissions, some 8

million tons per year, came from fossil fuel

production, with 90 per cent emitted in the

Northern Hemisphere. The team estimated

US ethane emissions at 2.4 million tons per

year for the 1990s, four times higher than the

official inventory from the US Environmental

Protection Agency for the same period.

This, they say, suggests a significant

under-estimation of methane emissions from

energy production in the US.

Olive Heffernan

Earth science

Gas copies carbon

Science 322, 1085-1088 (2008)

Carbon dioxide sucked up by plants during

photosynthesis is accompanied by another

gas that could be used to trace the captured

carbon, suggests new research. Carbonyl

Paleoclimate

Monsoon misery

Science 322, 940–942 (2008)

China’s Ming Dynasty once commanded

a million-man standing army and a fleet

of treasure ships. But still more powerful,

suggests new research, was the Asian

Monsoon. Natural fluctuations in the

seasonal wind appear to have triggered

the Mings’ overthrow and other historic

milestones — but during the last 50 years,

human influences have taken over as the

driver of monsoonal changes, say scientists.

In a Chinese cave on the fringes of the

monsoon’s range, a team led by Hai Cheng

of the University of Minnesota, found a

1,810-year-old stalagmite that proffers

an unusually detailed record of past

monsoon seasons. By analysing a range

of isotopes from the stalagmite’s layers,

Cheng’s team found that for centuries

the strength of the monsoon was

associatedwith natural factors such as

solar variation and average Northern

Hemisphere temperatures. The timing

of major monsoonal shifts coincided

with the rise and fall of several Chinese

dynasties, implying that these societies’

agricultural foundations were at the

mercy of changing rainfall. The tables

turned, however, at around 1960, say

the researchers, when the correlation

between the Asian Monsoon and

temperature switched.

The authors conclude that from the

mid-twentieth century, human-induced

climate change has superseded natural

variation as the dominant influence on

the monsoon.

SCIENCE / AAAS

Anna Barnett

STEVEN ALLISON

123RF.COM / DAVID GAYLOR

ISTOCKPHOTO.COM / OOYOO

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nature reports climate change | VOL 2 | DECEMBER 2008 | www.nature.com/reports/climatechange 153

research HIGHLIGHTS

sulphide (COS) will allow improved estimates

of global photosynthetic activity, an important

buffer against human-caused CO2 emissions

that has been notoriously difficult to quantify.

J. Elliott Campbell of the University

of Iowa and colleagues looked at

measurements of atmospheric COS, which

photosynthesizing plants take up in a similar

manner to carbon dioxide, from an airborne

experiment across the central and eastern

United States during July and August 2004.

They found plants drew down 4.2 times the

amount of COS predicted by past models,

which assumed that both photosynthesis and

respiration would control COS levels in the air.

The data instead matched a new model, drawn

from recent laboratory experiments, in which

photosynthesis alone is the main influence.

The finding that COS, unlike CO2, is not

released back to the atmosphere through

respiration makes the gas ideal for tracking

photosynthesis, the group concludes.

COS-based photosynthesis estimates could

clarify the relationships between plant

growth, CO2 levels and climate change,

adding precision to climate models.

Alicia Newton

anthropogenic change

Water vapour warming

Geophys. Res. Lett. 35, L20704 (2008)

Scientists have obtained the most detailed

ever measurements of atmospheric water

vapour — an abundant greenhouse

gas — from unique sensors aboard a NASA

satellite. The observational data validate what

scientists have inferred from climate models

for some time — that the heat-trapping

properties of water vapour could double the

effect of greenhouse warming from other

sources such as carbon dioxide.

A team led by Andrew Dessler at Texas

A&M University used data measured

by the Atmospheric Infrared Sounder

(AIRS) on NASA’s Aqua satellite from

2003 to 2008 to calculate the amount

of water vapour throughout the lowest

10 miles of the atmosphere. AIRS is the

first instrument capable of differentiating

the amount of water vapour at different

levels in the atmosphere, enabling these

detailed observations. Dessler and

colleagues combined the satellite data

with global-average surface temperature

readings for the same period to determine

how water vapour both affects, and

responds to, temperature. They found that

if the Earth warms by 1 °C, rising humidity

will trap an additional 2 Watts of energy

per square metre, similar to the estimates

simulated by climate models.

The results suggest that the feedback

effect of water vapour on climate warming is

both large and positive.

Olive Heffernan

Climate impacts

Fiery forecast

Global Biogeochem. Cycles 22, GB4007 (2008)

Fires fanned by drought and deforestation

could consume much of the Amazon

rainforest over the twenty-first century,

reports a new study. Numerous climate

models project worsening dry seasons in

the Amazon, but the impact on fire risk,

and its interaction with deforestation, is less

well-understood.

Nicola Golding and Richard Betts,

of the Met Office Hadley Centre, UK,

combined a global climate model with a

fire danger index to simulate changes in fire

risk in the Amazon until 2090. According

to the model, an area of high fire risk

could spread along southeast Amazonia

as early as the 2020s; by the 2080s, at least

50 per cent of the forest — up to 93 per cent

in some model runs — lies in the danger

zone. Compounding the threat, growing

areas of fire risk in eastern Amazonia are

likely to overlap with expanding areas of

slash-and-burn forest clearing, raising the

chances that intentional fires will spread.

The researchers warn that if the regional

climate changes simulated for Amazonia

hold true and deforestation continues, the

entire eastern portion of the rainforest

could be at risk by 2080. The loss of forest

cover might further intensify regional

droughts, they note, and would remove one

of the planet’s sizeable carbon sinks.

Anna Armstrong

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