Articles in 2021

CMIP6 models simulate higher and more accurate cloud liquid water fraction relative to CMIP5, but both ensembles overestimate warm cloud precipitation. Correcting these warm cloud processes in a model exposes compensating biases large enough to offset CMIP5–CMIP6 climate sensitivity differences.

Current and future climate change is expected to impact human health, both indirectly and directly, through increasing temperatures. Climate change has already had an impact and is responsible for 37% of warm-season heat-related deaths between 1991 and 2018, with increases in mortality observed globally.

Coastal sea levels are impacted by local vertical land motion plus local and remote changes to ocean circulation, density and mass changes. Tide-gauge records are used to reconstruct the coastal sea-level budget over nine regions, showing its variability has been dominated by ocean circulation since 1960.

The authors model the role of algal symbiont shuffling and evolution in coral resilience to warming and ocean acidification, globally. They find that shuffling is more effective than evolution, and show global patterns of vulnerability due to the interaction of warming rate and adaptive capacity.

Using mechanistic models that incorporate visual foraging and temperature-driven physiology for two fish types, the authors reveal how latitudinal light gradients, which are not affected by climate change, can constrain warming-related shifts to high latitudes.

Marine low clouds cool the planet, but their response to warming is uncertain and dominates the spread in model-based climate sensitivities. Observational constraints suggest smaller cloud feedbacks than previously reported and imply a more moderate climate sensitivity.

Climate change impacts precipitation patterns, and thus the risk for drought. Damages from drought in Europe will increase with losses more than €65 billion per year in a scenario without climate mitigation; keeping warming below 2 °C avoids most impacts.

The amount of carbon stored in African ecosystems and how climate change will affect this is uncertain. Projections indicate that carbon storage will increase in East Africa, climate change will have an overall negative impact on woody biomass and that other human pressures will amplify the trend.

Global warming-driven deglaciation in high-mountain Asia raises the likelihood of natural dam failure and associated glacial lake outburst flood risk. This is estimated for lake development under present-day and future warming scenarios, highlighting emerging hotspots and transboundary impacts.

Carbon loss from forests occurs through deforestation or the degradation of existing forest. The loss of forest area in the Brazilian Amazon was higher in 2019 than following drought and an El Niño event in 2015, yet degradation drove three times more biomass loss than deforestation from 2010 to 2019.

Disturbance regimes from fire, drought, harvest and insects will probably intensify in the future and under climate change. Despite partial offsets from regrowth, disturbance from fire and harvest reduces carbon uptake and storage in boreal forests, impacting the strength of this carbon sink.

There is a mismatch between emission estimates from global land use calculated from IAMs and countries’ greenhouse gas inventories. This study presents a method for reconciling these estimates by reallocating part of the land-use sink, facilitating progress assessment towards climate goals.

Mesoscale eddy variability has increased in eddy-rich regions by 2–5% per decade but decreased in the tropical ocean over the satellite record (1993–2020). These changes will impact ocean–atmosphere heat and carbon exchange, with implications for regional and global climate.

Mountain snowpack declines are often tracked using snow water equivalent trends sensitive to highly variable precipitation. Observational work proposes temperature-driven daily snowmelt during the accumulation season as an alternative metric, with increases that are three times more widespread.

Changes in lightning activity are uncertain under climate change. The authors project that summer lightning in the Arctic is likely to more than double by the end of the century, with implications for lightning-strike tundra wildfires and associated carbon release from permafrost.

Agricultural productivity has increased historically, but the impact of climate change on productivity growth is not clear. In the last 60 years, anthropogenic climate change has reduced agricultural total factor production globally by 21%, with stronger impacts in warmer regions.

Modelling riverine fish growth across warm and cool sections of a river network, the authors demonstrate that habitats that are suboptimally warm in summer may actually provide the majority of growth potential. This highlights a risk in conservation strategies that devalue ephemerally warm habitats.

The impact of glacier retreat on fungal-driven decomposition in rivers is investigated using a standardized test across six countries. Less glacier cover is linked to increased decomposition, which is in turn associated with a greater abundance of fungi and a fungal cellulose-degrading gene, cbhI.

Model projections of future drylands distribution using a proxy based on atmospheric aridity show expansion under climate change, but may not be an accurate representation. An alternative index based on ecohydrological variables such as water limitation shows no global expansion of drylands.

Land subsidence and uplift influence the rate of sea-level rise. Most coastal populations live in subsiding areas and experience average rates of relative sea-level rise three to four times faster than due to climate change alone, indicating the need for policy to address subsidence.