Letters in 2019

Aviation’s contribution to global emissions is increasing and requires action. This paper shows that the International Civil Aviation Organization plan to offset increasing emissions will not be realized unless robust criteria for the eligibility of offset credits are adopted.

Abrupt community shifts, for marine species from zooplankton to fish, are shown to occur with local climate changes in which warming pushes species beyond their thermal niche. This modelling approach suggests future events will be larger and have more broad-reaching impacts.

Warming is altering subtropical precipitation; however, it is not clear whether this will continue in an equilibrium climate. Using projections to 2300, Southern Hemisphere drying is shown to be a transient response to the meridional temperature gradient changes.

Greater land–sea temperature contrast under anthropogenic warming will enhance aerosol concentrations, reveal model simulations, linked to reductions in large-scale cloud cover and corresponding decreases in precipitation and aerosol wet removal.

Up to 35,000 lakes in the Northern Hemisphere may be at risk of intermittent winter ice cover at 2 °C warming, reveals an observation-based study. This would affect 394 million people reliant on lake ice for ecosystem services.

Climate change will alter primary productivity in the Southern Ocean, and warming and iron limitation will influence the composition of diatoms in the region. Optimum growth temperatures are wider than expected, but limited iron will affect which species flourish.

The compensation between atmospheric and oceanic heat transports under anthropogenic warming can be linked to the combined impact of Atlantic Meridional Overturning Circulation weakening, perturbations to Southern Ocean heat storage, and coupled responses of the Hadley and Subtropical cells.

As the southwest Atlantic sector of the Southern Ocean has warmed, the distribution of a key species, Antarctic krill, has contracted southwards. This has occurred in tandem with a decline in recruitment of juveniles, linked to increasingly positive anomalies of the Southern Annular Mode.

Groundwater model results and hydrologic data sets reveal that half of global groundwater fluxes may equilibrate with climate-driven recharge variations on human timescales, indicating that hydraulic memory may buffer climatic change impacts.

Bluetongue risk to livestock across northern Europe is projected to extend further north, with a longer transmission season and larger outbreaks on average. As a result, disease detection and control measures will be increasingly important.

The connections between Arctic sea-ice loss and severe Eurasian winters are complicated by differences among studies. Correcting model underestimates reveals that 44% of the central Eurasian cooling trend is attributable to sea-ice loss in the Barents–Kara Seas.

Synthetic aperture radar interferometry reveals that 19 Gt of ice is lost per year from glaciers in South America — mostly from Patagonia — contributing 0.04 mm annually to global sea-level rise.