Articles in 2020

Carbon dioxide removal (CDR) will be necessary to meet climate targets. Applying equity principles to allocate national CDR quotas shows a large variation across countries and principles, while within the EU domestic biophysical limits constrain individual capacity to achieve them.

The carbon footprint of oil refining differs depending on crude oil quality and refinery configuration. Analysis of global oil refining in 2015 shows refining carbon intensity at crude, refinery and country levels and highlights potential for emissions reductions.

Warming is predicted to weaken the Atlantic Meridional Overturning Circulation. Simulated temperature stabilization at Paris Agreement targets shows recovery to a level independent of the target, with continued North Atlantic warming and North Atlantic sea-level rise lower than the global mean.

Algal movement through the water column occurs to maximize photosynthesis and avoid predation. Increased CO₂ concentrations are shown, from laboratory and field experiments, to reduce motility in algal species in fresh, brackish and marine systems.

Evapotranspiration links productivity with water cycling between land and atmosphere. A model including plant hydraulics better describes the response of evapotranspiration to stress from vapour pressure deficit and soil moisture under rising temperatures than approaches common in Earth system models.

Human waste in slums is often collected untreated in pit latrines, which emit GHGs and have negative impacts on human health. If adopted in slums globally, off-site composting could reduce methane emissions from the sanitation sector by 13–44% while improving public health.

Marine biodiversity is at risk as the ocean warms, but currently the focus has been at the surface as the deep ocean has warmed less. Climate velocity—the speed and direction of isotherm displacement—is calculated to be faster in the deep ocean, and projections show this difference will grow.

Poverty increases vulnerability to climate-related shocks and both drive migration decisions. In a laboratory-based economic game, Marotzke et al. find that the rich are unable to prevent migration by the poor, and increase their effort to avert climate change when the poor are hit by a climate event.

Predicting the impact of climate change on snowstorms is key for future water resource estimates. North American snowstorms are tracked in high-resolution warming simulations and exhibit robust decreases in storm count, snow water equivalent and areal footprint, particularly in shoulder seasons.

COVID-19 pandemic lockdowns have altered global energy demands. Using government confinement policies and activity data, daily CO₂ emissions have decreased by ~17% to early April 2020 against 2019 levels; annual emissions could be down by 7% (4%) if normality returns by year end (mid-June).

The Barents Sea cools the ocean, and dense water masses form that flow into the global overturning circulation. Hydrographic observations from 1971 to 2018 show reduced cooling efficiency with warmer Atlantic inflow, reduced sea ice and reduced wind-driven heat loss.

The impact of climate change on the circumpolar distribution of the key Antarctic food-web species, krill, is unknown. Combining a krill growth model with projected climate scenarios shows the growth habitat is likely to experience only moderate change, with the northern edges most at risk.

Climate warming increases evapotranspiration (ET) more in boreal peatlands than in forests. Observations show that peatland ET can exceed forest ET by up to 30%, indicating a stronger warming response in peatlands. Earth system models do not fully account for peatlands and hence may underestimate future boreal ET.

Plant pathogens threaten food security and ecosystem health. Projections of potential fungal plant pathogens under different warming and land-use scenarios indicate that warming temperatures under climate change will lead to increases in the relative abundance of such pathogens in most soils worldwide.

Shorefast sea ice, which forms along the Arctic shore in winter and spring, is important for local communities and ecosystems. Satellite and climate model data are used to estimate a decrease in shorefast ice season length of 5–44 days by 2100, with the coldest areas experiencing the largest reductions.

Crabeater seals feed predominantly on Antarctic krill. Combining seal tracks and diving behaviour with environmental variables allows the future foraging habitat, and therefore krill distribution, to be predicted, suggesting a shift offshore and south along the western Antarctic Peninsula.

Under rising CO₂, most plants constrict their stomata, lose less water via transpiration and photosynthesize more efficiently. A global dataset of tree-ring isotope measurements reveals a slowdown in water-use efficiency gains over the twentieth century, with marked spatiotemporal variability.

Despite strict controls on precursor emissions, ozone air pollution has not decreased over Europe in recent decades. This is largely attributed to water-stressed vegetation; during heatwaves and drought, plants are less effective at ozone removal via stomata, worsening peak ozone pollution episodes.

Climate warming causes less mountain precipitation to fall as snow. Hydrologic simulations predict that in a high-end emissions scenario, this decreases the predictability of seasonal water resources across the western United States, with low-elevation coastal areas impacted most strongly.

This analysis of global climate policy reports shows how economic ideas have shaped climate policy. The authors find a shift from neoclassical dominance to a more diversified discourse, which has expanded policy choices beyond market-based policies to include green innovation and industrial policy.