Research articles

Global climate models have a well-known bias in the position and strength of the Southern Hemisphere westerly winds. Research reveals that this bias increases carbon uptake by the ocean, reducing atmospheric carbon dioxide concentrations, in climate model simulations—a result that should help constrain uncertainties in climate model projections.

The ‘pathway’ the world needs to follow to limit global temperature rise to 2 °C remains uncertain. Analysis that takes technical and economic constraints on reducing emissions into account indicates that emissions need to peak in the next decade and then fall rapidly to have a good chance of achieving this goal.

Substituting fossil fuels with bioenergy from forests, as well as thinning forests to reduce wildfire emissions, has been proposed as a means of cutting carbon dioxide emissions. A study based on inventory data for US West Coast forests now challenges this proposal, and finds that it could lead to 2–14% higher emissions than current management practices over the next 20 years.

The West Antarctic Peninsula has experienced rapid warming in recent decades. One of the effects has been a loss of the ‘fast-ice’ skin, or frozen layer, that forms on the sea surface each winter and reduces seabed scouring. A study now links increased seabed scouring over the past 25 years to higher benthic mortality, with implications for the region’s biodiversity.

Little information exists to guide conservation planning under climate change uncertainty. Now a study combines ecological predictions with an economic decision framework to investigate strategies to minimize extinction risk in one of the world’s most threatened ecosystems—the South African fynbos. The research finds that the best conservation options vary nonlinearly with available budget.

In some decades, such as 2000–2009, the observed globally averaged surface-temperature time series has shown a flat or slightly negative trend. A modelling study provides evidence that heat uptake by the deep ocean may cause these hiatus periods and may be linked to La Niña-like conditions.

Climate impacts on biodiversity are usually assessed at the morphospecies level. An analysis of the distribution and mitochondrial DNA variability of nine montane aquatic insect species in Europe suggests range contractions will be accompanied by severe loss of genetic diversity. These results imply that morphospecies-scale assessments may greatly underestimate potential biodiversity losses from climate change.

Ocean acidification poses a threat to marine calcifiers, but their response varies widely. An analysis of Mediterranean corals and molluscs now shows that the ability to continue shell and skeleton growth in corrosive seawater is determined in part by the existence of outer organic protective layers. High temperatures, however, modify resistance to acidification.

Enhanced tropical forest productivity, facilitated by increasing carbon dioxide concentrations, could act as a substantial carbon sink. However, a long-term field experiment shows that increased leaf-litter inputs to the soil as productivity rises could stimulate the release of significant amounts of soil carbon, partially offsetting predicted gains in carbon storage.

Managed relocation, whereby species are moved to a more suitable habitat, has been proposed as a means of combating negative climate-change impacts on biodiversity. A quantitative decision framework to evaluate the optimal timing of relocation shows that in some cases, such as when population size is small, haste is ill advised.

The abundance of persistent organic pollutants (POPs) in the Arctic atmosphere has decreased over recent decades owing to international restrictions and regulations. However, an analysis confirms that warming is remobilizing POPs into the atmosphere from sinks such as snow and ice, a process that will increase the risk of exposure to these toxic chemicals.

The hydrological cycle is ultimately driven by solar energy, so it is not surprising that energy constraints affect the response of rainfall to climate change at a global level. Now analysis shows that the regional response of rainfall to greenhouse-gas-driven warming can also be understood from an energetic perspective.

The importance of disease in modulating ecosystem responses to climate change remains poorly understood. A seven-year study of the effects of increased snow cover on tundra plant communities in Sweden found that, although plant growth was favoured by increased snow, biomass and carbon-balance trends were reversed by a pathogen outbreak.

Preventing deforestation—a key goal of international climate policy—can incur an opportunity cost for local communities who depend on forest resources for their livelihoods. A study compares the cost of carbon conservation through forest protection with that of a scheme that directly alleviates the demand for forest conversion.

Subzero temperatures at high latitudes typically restrict shipping but facilitate ground transportation. A study quantifies the impacts of climate change on Arctic transportation by mid-century and finds that all eight Arctic states will probably suffer steep declines in inland transport, but will reap the benefits of faster sea travel.

Ocean acidification due to anthropogenic carbon dioxide emissions has negative effects on many marine organisms, but the long-term impacts are less well known. A study into the effects of natural carbon dioxide seeps on coral reefs and seagrasses confirms model predictions that acidification may contribute to reduced diversity and resilience.

Our ability to predict El Niño/Southern Oscillation (ENSO) activity is hampered by the relatively short length of the instrumental record. An annually resolved record of ENSO variability over the past millennium based on tree rings indicates that ENSO amplitude varies on a 50–90 year cycle, providing an important constraint for improving predictions.

Thaw-lake expansion is enhanced by climate warming, potentially feeding back to boost warming further. A new landscape-scale modelling study of the life cycle of Siberian thaw lakes indicates that drainage strongly limits lake expansion. This results in methane-emission estimates that are substantially lower than previously suggested.

Expanding biofuel production into agricultural land reduces the need to clear natural ecosystems and can benefit the global climate through reduced greenhouse-gas emissions. A remote-sensing study of the Brazilian cerrado now provides empirical evidence that sugar-cane expansion also cools local climate directly by altering surface reflectivity and evapotranspiration.

Small temperature increases will benefit the growth of many cold-blooded animals, but laboratory studies indicate that warming can eventually exceed physiological limits, resulting in reduced growth. Evidence shows that this may have already happened for a fish species—the banded morwong—in the Tasman Sea.