Research articles

As the global climate changes, drought is expected to reduce productivity and tree survival across many forests; however, the relative influence of climate variables on forest decline remains poorly understood. A drought-stress index based on tree-ring data—newly developed for the southwestern United States—is found to be equally influenced by evaporation (primarily temperature driven) and precipitation and may serve as a holistic forest-vigour indicator in water-limited forests.

Comprehensive computer simulations show that coral reefs are likely to suffer extensive long-term degradation resulting from mass bleaching events even if the expected increase in global mean temperature can be kept well below 2 °C. Without major mitigation efforts to limit global warming significantly, the fate of coral reef ecosystems seems to be sealed.

Climate-driven sea-level rise will result in coastline retreat due to landward movement of the coastal profile. However, coastlines adjacent to tidal inlets will also be influenced by changes in the rate of basin infill and variations in rainfall. A model demonstrates that typical practice, which fails to incorporate these processes, is liable to represent only 25–50% of total coastline change.

Accurately characterizing natural versus forced sea surface temperature variability in observations is needed to validate and verify climate models used for projections of future climate change. This study successfully resolves previous large discrepancies in estimated tropical Indo-Pacific twentieth-century trends between observationally based sea surface temperature reconstructions.

An international agreement on reducing greenhouse-gas emissions requires large financial flows from richer to poorer countries. However, the amount and justification for such transfers is still contested. Now research has developed an argument for transfer payments by estimating regional carbon prices versus a global price, and found that in the case of a global carbon price of US$35 per tonne of carbon dioxide, a flow of US$15–48 billion per year would be needed.

The 2010 Cancún Agreement established a financial mechanism, through the Green Climate Fund, to support developing countries in greenhouse-gas emissions abatement. However, the different countries’ financial needs are often assessed on the basis of top-down cost estimates of energy technologies. Now a study provides a more fine-grained bottom-up approach that highlights the need for a ‘fair’ baseline calculation methodology and calls for a phase-out of fuel subsidies.

Sea-surface-temperature proxy data for a period of natural climate warming during the Pliocene are used in this study to show how palaeoclimatic data can help ‘ground truth’ numerical models, increasing the confidence in these same models for projecting future climate.

Focusing on New York City, this study investigates the impact of climate change on hurricane storm surges. The analysis shows that the frequency of surge-flooding events is likely to increase greatly owing to the combined effects of storm-climatology change and sea-level rise.

Assessments of tropical cyclone risk trends are typically based on reported losses, which are biased by improvements in information access. Now research based on thousands of physically observed events and contextual factors shows that, despite projected reductions in tropical cyclone frequency, projected increases in demographic pressure and tropical cyclone intensity can be expected to exacerbate disaster risk.

Greenhouse-gas emissions are likely to have an impact on the damage caused by extreme weather events, such as tropical cyclones. A study predicts that climate change will increase the frequency of these high-intensity storms in selected ocean basins and double their economic damage. Almost all tropical cyclone damage tends to be concentrated in North America, East Asia and the Caribbean-Central American region.

Global climate models cannot resolve hailstorms explicitly, so it is unclear whether a warmer climate will change hailstorm frequency and intensity. Now a study using high-resolution model simulations capable of resolving hail indicates the near-elimination of hail at the surface in future simulations for Colorado—a major centre of hailstorms in the United States.

Aviation is known to affect climate by changing cloudiness, but the magnitude of this effect remains uncertain. A modelling study indicates that changes in cloudiness associated with spreading of the line-shaped contrails that form behind aircraft may cause almost an order of magnitude more warming than the contrails alone.

Vehicle-emission standards for non-carbon-dioxide pollutants have recognized benefits for air quality. An interdisciplinary analysis now shows that adopting tight on-road emission standards for these pollutants would also mitigate short-term climate change and provide large benefits for human health and food security in a number of developing countries.