research highlights

radiation, organic matter both scatters Claire Hughes, from the University policies are more useful for climate and absorbs radiation. The absorptive of East Anglia, and colleagues, change mitigation. MC component of organic matter is brown measured biogenic bromocarbons and carbon, and is currently ignored in most biological parameters in coastal waters REGIME CHANGE climate models. Its exclusion results in and the atmosphere of the western Savannah Shift organic matter being considered as a Antarctic Peninsula. The sampling Nature http://doi.org/h3c (2012) cooling agent, ignoring the potential encompassed all seasons over a number warming component. of years. Chul Chung, from the Gwangju Institute Samples from diatom blooms showed of Science and Technology, and co-workers, significantly higher bromocarbon investigated the radiative forcing of carbon concentrations than non-bloom waters, aerosols using observations from both with the sea-to-air flux of biogenic satellite- and ground-based work, for the bromine increasing by a factor of 3-4. This period 2001–2009. suggests that non-bloom conditions could Brown carbon is found to contribute decrease the atmospheric bromine level, ~20% to carbon aerosol absorption globally, and therefore feedback on atmospheric meaning organic matter has a net effect of composition and chemistry. BW radiative forcing that is close to zero. They

find a larger radiative forcing from carbon ECONOMICS VISION/THINKSTOCK ANUP SHAH/DIGITAL aerosols than has been previously reported, Responsibilities shared © due to the inclusion of brown carbon, Ecol. Econ. http://doi.org/h29 (2012) which is at least comparable to that caused Climate change will affect all ecosystems, by methane. Carbon aerosols are shown to and when they reach tipping points, regime have a net warming effect, even in regions shifts may occur. Vegetation areas may where previously scattering by organic shift to alternative states. The savannah matter was thought to negate the warming by complex — which encompasses the vast black carbon. BW grassland, savannah and forest ecosystems of tropical and subtropical regions — is MARINE BIOGEOCHEMISTRY known to undergo regime shifts and the Algae to atmosphere large areas involved means that future shifts Global Biogeochem. Cy. http://doi.org/ will be of global importance. h3b (2012) Steven Higgins, of Goethe University Frankfurt, and Simon Scheiter, of the Senckenberg Nature Research Society, use a dynamic global vegetation model to predict

ISTOCKPHOTO/THINKSTOCK the effect of increasing atmospheric carbon © dioxide concentrations on vegetation states in the savannah complex. They observed Allocating the carbon emissions that are vegetation shifts between the years 1850 associated with products exchanged in the and 2100. Each regime moved to a higher international market to the producers or vegetative state, for example deserts to consumers of the goods is critical for global grasslands, and grasslands to savannahs. As climate policy. modelled future precipitation is uncertain, María-Ángeles Cadarso of the they assumed rainfall remains as it is today, Universidad de Castilla-La Mancha, Spain, so future work will need to investigate and colleagues outline the idea of ‘shared whether this would alter projections. They CLAIRE HUGHES

© responsibility’ between both buyers and conclude that atmospheric carbon dioxide sellers as a way of allocating emissions from has been, and will continue to be, a key The structure of marine ecosystems, and internationally traded goods according to factor shaping vegetation landscape, with associated biogeochemical cycles, will be the value added by countries to each step of local changes occurring more rapidly than affected by climate change and increased the global product chain. They apply their global changes. BW human activity. Marine phytoplankton model to the Spanish economy, divided into produce a wide range of trace gases, 46 sectors, during the period 2000–2005. Written by Alastair Brown, Monica Contestabile and and it has been suggested these gases They first allocated the emissions from Bronwyn Wake. play a role in controlling atmospheric imported goods only to Spain and found chemistry. Bromocarbons — produced by that the country’s total emissions increase diatoms — are released to the atmosphere by 40.8% in 2005. Using the shared- as inorganic bromine, which interacts with allocation model, Spain’s total emissions ozone and dimethyl sulphide, and has a were found to increase by only 34.4% role in cloud formation. Climate-induced in 2005. changes in phytoplankton composition The researchers conclude that using could lead to altered gas release to a shared-allocation approach would the atmosphere. help to discriminate which economic

NATURE CLIMATE CHANGE | VOL 2 | AUGUST 2012 | www.nature.com/natureclimatechange 571

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