Research articles

Climate change is expected to increase the intensity of precipitation in many regions. Experiments show that small increases in precipitation intensity, but not total amount, can lead to deeper penetration of water into the soil, leading to greater woody plant growth at the cost of grasses in a savannah system.

Climate change is altering the seasonal distribution, interannual variability and overall magnitude of precipitation. A new global measure of precipitation seasonality is proposed, and application of this method to observations from the tropics shows that increases in variability were accompanied by shifts in seasonal magnitude, timing and duration.

Rising temperatures may alter the proportions of both heat- and cold-related deaths, leaving the net impact on annual mortality uncertain. Current and future seasonal patterns of temperature-related mortality in Manhattan, New York, are estimated, showing warm season increases and cold season decreases in temperature-related mortality, with positive net annual deaths in all cases.

Climate change is expected to significantly influence biodiversity, but the performance of climate change mitigation strategies in reducing these impacts is not yet known. Simulations of the future ranges of common and widespread species indicate that mitigation could reduce range loss by 60% if emissions peak in 2016, or by 40% if emissions peak in 2030.

Climate-induced shifts in crop mix may affect the grain transport system. In the US, evidence now shows that changing crop mixes reduce the importance of Lower Mississippi River ports, but increase the role of ports in the Pacific Northwest, Great Lakes and Atlantic.

Future tropical cyclone activity is investigated around the Hawaiian Islands. Projections show a consistent and robust increase in the frequency of tropical cyclones by the end of the century. This increase is attributed to changes in large-scale circulation, which alters the cyclone tracks.

The causes of interannual variability in Arctic sea-ice extent are not well understood. This study looks at the impact of the greenhouse effect, associated with clouds and water vapour, on sea-ice formation and melt. Enhancement of the greenhouse effect, due to increased cloudiness and humidity, results in increased ice melt.

Two dynamical methods are used at present to project sea-level changes during the next century—process-based and semi-empirical. However, semi-empirical projections can exceed process-based projections three-fold. This work tests the robustness of semi-empirical projections to the underlying assumptions, and finds these projections are sensitive to the dynamics considered and the terrestrial-water corrections applied.

This study looks at the pace of change in climate zones as a function of global warming. Using the RCP8.5 scenario, the rate nearly doubles by the end of this century, and about 20% of all land area undergoes a change. In the future, species will have less time to adapt, therefore increasing the risk of extinction.

Short-lived climate pollutants are known to contribute to global warming, but the impact of this increased temperature on sea-level rise due to thermal expansion is not known. Curbing emissions of these pollutants is shown to significantly reduce the rate of sea-level rise by 24–50% by 2100; however, delaying mitigation by 25 years reduces the impact on sea-level rise by about a third.

The sensitivity of the terrestrial biosphere to changes in climate constitutes a feedback mechanism with the potential to accentuate global warming. Process-based modelling experiments now indicate that under a business-as-usual emissions scenario the biosphere on land is expected to be an increasingly positive feedback to anthropogenic climate change, potentially amplifying equilibrium climate sensitivity by 22–27%.

Most weather-related aircraft incidents are caused by atmospheric turbulence; however, the effects of changing climate are not known. Climate model simulations show that clear-air turbulence, associated with jet streams, changes significantly for the transatlantic flight corridor when atmospheric carbon dioxide is doubled. These results suggest that climate change will lead to bumpier transatlantic flights by the middle of this century.

In recent years the global warming trend has plateaued, despite increasing anthropogenic emissions. Now research attributes this plateau to an increase in ocean heat uptake, through retrospective predictions of up to 5 years in length. The ability to hindcast this warming plateau strengthens our confidence in the robustness of climate models.

Sahelian drought is investigated by analysing de-trended observations between 1900 and 2010, which show that substantial Northern Hemisphere volcanic eruptions preceded three of the four driest summers. Modelling both episodic volcanic eruptions and geoengineering by continuous deliberate stratospheric injection shows that large asymmetric aerosol loadings in the Northern Hemisphere are a precursor of Sahelian drought, whereas if the aerosol loadings are concentrated in the Southern Hemisphere greening of the Sahel is induced.

This study shows that climate change could lead to a major redistribution of vegetation across the Arctic, with important implications for biosphere–atmosphere interactions, as well as for biodiversity conservation and ecosystem services. Woody vegetation is predicted to expand substantially over coming decades, causing more Arctic warming through positive climate feedbacks than previously thought.

Research combining the analysis of coral distribution in volcanically acidified waters with laboratory culture experiments indicates that reef communities may shift from reef-building hard corals to non-reef-building soft corals under CO₂ partial pressure ( $p_{{\text{CO}}_2}$ ) levels of 550–970 μatm that are predicted to occur by the end of this century.

Has the frequency of ‘extreme weather events’ changed with climate warming over the last century? Using hourly precipitation records from thirteen sites, this study finds no evidence for significant changes in mean ‘storminess’ across the United States.

Estimating the probable magnitude of future sea-level rise under global warming is complicated by a limited understanding of long-term ice-sheet dynamics. This study presents a probabilistic approach for assessing upper bounds on twenty-first-century Antarctic ice-sheet loss, and its effect on sea level.

Pronounced increases in winter temperature result in lower seasonal temperature differences, with implications for vegetation seasonality and productivity. Research now indicates that temperature and vegetation seasonality in northern ecosystems have diminished to an extent equivalent to a southerly shift of 4°– 7° in latitude, and may reach the equivalent of up to 20° over the twenty-first century.

The Walker circulation is a large overturning cell that spans the tropical Pacific Ocean. Fluctuations in this circulation reflect changes in tropical heating, and have global impacts on temperature and precipitation. Analysis of trends in sea-level pressure from ten data sets reveals strengthening of the Walker circulation in line with increasing global temperature, which is counter to current model predictions.