Research articles

The proposed Keystone XL pipeline to connect Canadian oil sands with US refineries and ports has attracted much controversy. Based on an economic model, this study finds that the biggest emissions impact of the pipeline may be due to its effect of lowering global oil prices and, in turn, increasing global oil consumption (and related emissions). The analysis therefore points to a gap in existing assessments of the Keystone XL project.

European forest disturbance—due to wind, bark beetles and wildfires—has increased in association with climate changes, but future disturbance-response remains highly uncertain. Now, research based on an ensemble of climate change scenarios indicates that an increase in forest disturbance is probable in the coming decades, with implications for forest carbon storage.

The impacts of climate change on certain aspects of the El Niño/Southern Oscillation (ENSO) have been established. However, the change in sea surface temperature, commonly used to represent ENSO amplitude, remained uncertain. Now, the sea surface response is shown to be time-varying, with an increasing trend to 2040 followed by a decreasing trend. The previous uncertainty is attributed to the expectation of unidirectional behaviour and unrealistic model representations.

The Pacific trade winds have strengthened since the late 1990s, and there has been related strengthening of the atmospheric Walker circulation. Although the impacts of these changes are becoming known, their cause has not been identified. This study, using observations and models, shows that warming of the Atlantic sea surface and corresponding displacement of atmospheric pressure centres are key drivers.

This study shows that climate change has the potential to substantially increase undernourishment rates and threaten food security in developing countries through crop damage, but that ozone regulation can significantly offset climate impacts, depending on the scenario. The findings should help policymakers devise optimal strategies for food production under global climate change.

Earth system models do not currently account for unforced variability in land–atmosphere CO₂ flux when simulating the responses of the terrestrial carbon cycle to anthropogenically forced changes in climate and atmosphere. Now, research shows that this unforced variability is larger than the forced response in many areas of the world, precluding detection of the forced carbon-cycle change for decades.

Internal variability in the climate system makes it difficult to determine the rate of regional sea-level rise. This study uses satellite altimetry data and corrects for natural variability to determine the anthropogenic contribution to sea-level rise in the tropical Pacific region.

The current slowdown in global warming has raised questions about the accuracy of climate model projections. This work selects models that are largely in phase with the natural variability, in this case the El Niño/Southern Oscillation, of the climate system. The selected models are able to predict the recent Pacific Ocean temperature and spatial trends.

Reduced soil-carbon storage in response to warming is a potential reinforcing feedback that could enhance climate change. A study now shows that for tropical montane wet forest, long-term warming (represented by an altitudinal gradient) accelerates below-ground carbon processes but has no apparent impact on soil-organic-carbon storage.

Nitrous oxide (N₂O) is a greenhouse gas and an important ozone-depleting substance. Microbial nitrogen cycling in agricultural soils is a major source of atmospheric N₂O. Now, research shows that the capacity of soils to take up N₂O is mostly explained by the abundance and diversity of a newly described N₂O-reducing microbial group.

Technology is expected to play an important role in climate change adaptation, but little is known about whether it is actually being transferred to developing countries. Research now shows that in most of the adaptation projects managed by the Global Environment Facility, technology transfer is occurring mainly in the form of early deployment of existing technologies.

Historical aerosol forcing from large volcanic eruptions are reconstructed from sulphate deposition measured in ice cores. This study updates these records by using a more extensive collection of Antarctic ice cores, which provide new records and accurate dating of published records. The results show that prior to the year 1500 the reconstructions were either previously overestimating global aerosol forcing by 20–30% or underestimating it by 20–50%. This has implications for estimates of climate sensitivity.

Deforestation affects climate, biodiversity and other ecosystem services. This study quantifies Indonesia’s increasing rate of primary forest loss, which runs counter to the declining rates of loss in Brazil. The results highlight the value of thematically consistent and spatially and temporally explicit information in tracking forest change.

Widespread forest die-back due to the increasing frequency and intensity of drought in many parts of the planet is focusing attention on the mechanisms of tree drought resistance. This study provides direct experimental evidence that greater non-structural carbohydrate concentrations before drought help maintain hydraulic function and thereby prolong drought tolerance in seedlings of ten tropical tree species.

The criteria used to classify species as being at risk of extinction are based on global population estimates, making global-scale analysis important for conservation. Now, a study projecting population dynamics of all 45 known emperor penguin (Aptenodytes forsteri) colonies indicates long-term decline, primarily due to altered Antarctic sea ice conditions.

An increase in extreme weather events in the Northern Hemisphere mid-latitudes has been proposed as a result of amplification of atmospheric planetary waves in the region. This study finds months of extreme weather are associated with amplified planetary waves, with different types of extreme events associated to differing degrees.

Atmospheric stagnation can have serious health implications due to increased pollution exposure. This study investigates how global warming will alter atmospheric circulation and the resulting changes in the frequency and persistence of stagnation events. The authors find an overall increase in the size of the population exposed to these events and highlight the need to evaluate air pollution management.

Linkages between neighbouring ecosystems are rarely considered when seeking to predict ecological responses to climate change. However, the finding that the impact of climate change on seagrass beds is mediated by the response of neighbouring coral reef habitats highlights the need for a broader-scale view of climate change impacts on ecosystems.

Intermittency is often cited as the single greatest hurdle to making a transition from a fossil-based power system to one based on renewables. This study shows that a network of solar power plants, located in deserts, could provide significant baseload in four world regions, suggesting that decarbonization of the power system may be possible and affordable, even if no new technologies come online.

Crustose coralline algae (CCA) are potential ‘poster children’ of ocean acidification stress, yet their stress responses have been poorly studied in a natural or ecological context. Now, a comparison of historical and modern specimens from a site with a declining pH trend over a 30-year period reveals trade-offs in skeletal traits tied to calcium carbonate use in response to ocean acidification in four CCA species.