Letters in 2019

Future climate conditions threaten crops in sub-Saharan Africa. It is shown that most major sub-Saharan African crops have wild relatives that occur in regions better suited for future climate conditions, suggesting an opportunity for adaptation that does not require the adoption of new production systems.

The Indian Ocean is warming at an accelerated rate, and modelling experiments show teleconnections affecting the Atlantic meridional overturning circulation (AMOC). In a warming climate, reduced tropical Atlantic rainfall causes salinity changes strengthening the AMOC, while other factors weaken it.

Bananas are a staple food crop and important agricultural export for many countries. Here, it is shown that global banana yields have increased historically and will continue to increase in Africa but reduced yields are expected among the larger producers.

The supply of dense Antarctic Bottom Water to the Atlantic overturning circulation has declined in recent years. Observations show that since 2014 this has stabilized and slightly recovered due to variability in upstream dense waters, with implications for the global climate.

Along the West Antarctic Peninsula, a 25-year dataset indicates that oceanic CO₂ uptake depends on upper ocean stability and phytoplankton dynamics. Diatoms achieve high oceanic CO₂ uptake and uptake efficiency. There has been a nearly fivefold increase in oceanic CO₂ uptake due to sea ice changes.

Climate models project an increase in summer weather persistence for the northern mid-latitudes. In a 2 °C world, two-week-long hot-and-dry conditions increase by up to 20% for eastern North America. The chance of a week of heavy rainfall increases by 26%, adding to the risk of extremes in the future.

Fires play an important role in ecosystem dynamics. Long-term controls on global burnt area include fuel continuity and moisture, with ignitions and human activity becoming dominant in specific ecosystems. Changes in fuel continuity and moisture are the main drivers of changes of fire globally.

Climate change will increase meltwater and iceberg discharge from Antarctica, with implications for future climate and sea levels. Iceberg melt will partly offset greenhouse warming in the Southern Ocean and dampen the positive feedback loop between ice-sheet melting and subsurface warming.

Additional electricity generation is required to compensate for losses from inefficient transmission and distribution infrastructure. In this study, emissions from compensatory generation and the potential for reductions are estimated for 142 countries.

Elevated CO₂ increases plant biomass, providing a negative feedback on global warming. Nutrient availability was found to drive the magnitude of this effect for the majority of vegetation globally, and analyses indicated that CO₂ will continue to fertilize plant growth in the next century.

Lack of information is a barrier to climate change adaptation, and filling the information gap is a key component of adaptation projects. However, using a randomized controlled trial, this study finds no impact of a capacity-building workshop on community water management practices in Costa Rica.

Projections of temperature often focus on maximum warming levels, with variability less often considered. Investigating decadal variability in models shows those with higher equilibrium climate sensitivity also have a higher chance of super warming, and hiatus periods.

Exposure to dangerous heat following a major tropical cyclone is possible along coastlines globally. In a warmer world, the population at risk from this combination of extreme weather could rise markedly.

Island species are at risk as the climate changes. Island conifers are used as a model species and a combination of native and non-native occurrence data allows identification of realized, tolerable and fundamental niches; linking to island size provides an estimate of extinction risk.

Physically connected habitats are required for terrestrial species to shift their liveable ranges as the tropics warm. The authors show that over half of tropical forest area is currently unable to provide such climate connectivity, and that loss of connectivity is accelerating with deforestation.

Mass summertime fish die-offs across 359 Wisconsin lakes are attributed to high lake temperatures during periods of extreme heat, while infectious disease and winter conditions are shown to be poor predictors. Die-offs are projected to double by 2050 and quadruple by 2100 in north temperate lakes.

This study uses spatially explicit simulations of a simple coral reef ecosystem to show that evolutionary responses to shifting environmental conditions fundamentally change effective conservation management strategies.

The length of the dry season over tropical forests is a determining factor of ecosystem health and drought risk. Hydroclimate and vegetation data show that dry season length has increased over the Congo rainforest since the 1980s, owing to both an earlier dry season onset and a delayed end.

To limit warming, a rapid reduction in coal use is needed. Early retirement of coal power plants by members of the Powering Past Coal Alliance, which includes mainly wealthy countries that use little coal, would have a modest climate impact. Prospects for expanding the Alliance are examined.

Bird numbers are declining globally, with sharp decreases in alpine and Arctic regions. Increases in primary productivity in the Arctic (known as greening) are linked to increased nest predation, highlighting how changing climate conditions can affect food web dynamics.