Letters in 2013

Statistical analysis of maize yields in the United States reveals a strong negative response to very high temperatures, and a relatively weak response to seasonal rainfall. Now simulations using a process-based model suggest that the most important effects of extreme heat are associated with increased vapour-pressure deficit—which contributes to water stress—rather than direct heat stress on reproductive organs.

The influence of relatively slow changes in sea surface temperature on regional climate variability can provide a basis for medium-term (seasonal to decadal) prediction of many environmental factors. Research now shows that the sea surface temperature in the tropical South Atlantic can act as a dominant driver of rainfall variability, and hence outbreaks of malaria in northwest India.

Individual labour capacity has reduced to 90% in peak months owing to environmental heat stress over the past few decades. Under the highest climate change scenario considered, model projections indicate a reduction in labour capacity to less than 40% by 2200 in peak months, with most tropical and mid-latitude regions experiencing extreme heat stress.

As the Earth continues to warm over the coming decades, spatially extensive or ‘mass’ coral bleaching events—induced by persistently high water temperature—are expected to threaten the survival of coral reef ecosystems. Bleaching ‘hazard’ maps based on ensembles of the latest climate models and emissions pathways quantify the potential for mitigation activities to buy these ecosystems a temporary respite from this threat.

A study that couples a barrier-island model with an agent-based model of real-estate markets shows that, relative to people with little belief in model predictions on climate change, informed property owners invest heavily in defensive measures in the short term. They then abandon coastal real estate when price volatility becomes significant.

Seamless quantification of past and present climate variability is needed to understand the Earth’s climate well enough to make accurate predictions for the future. This study addresses whether tree-ring-dominated proxy data properly represent the frequency spectrum of true climate variability. The results challenge the validity of detection and attribution investigations based on these data.

Research shows that incorporating energy consumption in a global climate model can explain past surface temperature changes of as much as 1 K in mid and high latitudes in winter and autumn over most part of North America and Eurasia. This study concludes that energy use should be considered as an additional forcing in simulations to project future climate change.

Soils are the largest repository of organic carbon in the terrestrial biosphere. Nevertheless, relatively little is known about the factors controlling the efficiency with which microbial communities utilize carbon, and its effect on soil–atmosphere CO₂ exchange. Now research using long-term experimental plots suggests that climate warming could alter the decay dynamics of more stable organic-matter compounds with implications for carbon storage in soils and ultimately climate warming.

Changing wind-wave climate has the potential to exacerbate, or negate, the impacts of sea-level rise in coastal zones. Results from the first community-derived multi-model ensemble of wind-wave climate projections show agreement over extended regions of the global ocean. Large uncertainty in available wave-climate projections is found to be due to downscaling methods.

Many plant species used for biofuel emit more isoprene—an ozone precursor—than the traditional crops they are replacing. A modelling study now indicates the potential for significant human mortality and crop losses due to changes in ground-level ozone concentrations that could arise from large-scale biofuel cultivation in Europe. These findings suggest that biofuel policies could have adverse consequences that should be evaluated alongside carbon-budgeting considerations before large-scale policies are implemented.

Climate models struggle to reproduce the amplitude of polar temperature change observed in palaeoclimatic archives. A synthesis of observational and model data was used to reconstruct atmospheric dust concentrations in the Holocene and Last Glacial Maximum. The impact of aerosols in polar areas is underestimated in simulations for dustier-than-modern conditions; the inclusion of the amplified response to aerosols at high latitudes would improve model predictions.