Articles in 2021

Atmospheric rivers, concentrated plumes of moisture important to extratropical precipitation, have not changed with historical warming. Model simulations suggest that this is due to the competing weakening effect of aerosols and strengthening effect of greenhouse gases, which dominates with future warming.

Forests take up carbon from the atmosphere but also change Earth’s surface energy balance through biophysical effects. Accounting for these shows that tropical forests have the highest mitigation potential; the climate benefit of higher-latitude forests is offset by their warming effects in winter.

Climate change–induced shifts in seasonal events are often studied at population levels, which can neglect the scale at which selection operates. Here, the authors show marked small-scale spatial variation for egg-laying timing of great tits and further link these changes to the health of nearby oaks.

Tropical cyclone winds intensify with warming but the impacts depend on global population, which is likely to peak by mid-century and then decline. Impact modelling suggests that stronger mitigation, under which warming would peak after the population begins to decline, may spare 1.8 billion people from impacts by 2100.

Residual flood damage (RFD), the remaining damage from floods after adaptation measures have been implemented, is estimated across the globe under various adaptation scenarios and climate projections. RFD remains high in some Asian and African regions, suggesting a limit to flood adaptation there.

The coastal northeastern United States is a warming hotspot, and observations identify a slower Atlantic overturning circulation and a positive North Atlantic Oscillation phase as drivers. Analysis suggests that low horizontal resolution probably hampers models’ ability to capture the spatial pattern of enhanced warming.

A climate model shows that hydrological cycle change drives ocean salinity increases, enhancing heat transport into the ocean and modulating near-term climate warming. This suggests that model spread in near-term climate sensitivity may be due in part to hydrological cycle and salinity differences.

The North Pacific Meridional Mode (NPMM) can trigger El Niño/Southern Oscillation (ENSO) events. Climate simulations suggest that with warming ocean temperatures, the NPMM’s impact on future ENSO strengthens, contributing to increased frequency of future extreme ENSO events and their predictability.

Ocean heat content is increasing, yet projections have not been constrained by observations. Using Argo data and CMIP6 models shows high climate sensitivity models overestimate increases; constrained projections estimate sea-level rise, from 0 to 2,000 m thermal expansion, of 17–26 cm by 2081–2100.

Climate mitigation will require allocations of emission allowances to nations. This study proposes a utilitarian benchmark to ensure equitable allocations whilst mitigating climate change.

Combining previous estimates in a multimethod approach, extreme sea levels are assessed under global warming levels of 1.5–5 °C at over 7,000 coastal sites worldwide. By 2100 or before, about 50% of locations exhibit present-day 100-year extreme sea levels at least once per year, even at 1.5 °C of warming.

The impact of climate warming on El Niño/Southern Oscillation (ENSO) amplitude is uncertain in centennial-scale model projections due to internal variability, but an ensemble of millennial-scale simulations suggests decreased ENSO amplitude in the equilibrium response to greenhouse gas forcing.

High-resolution climate models exhibit reduced tropical Pacific mean-state biases due to better representation of ocean mesoscale processes, like tropical instability waves. With climate warming, these improved dynamics project weaker El Niño/Southern Oscillation sea surface temperature variability.

The authors investigate temperature and pH effects on fitness of an abundant marine crustacean (copepod) across 25 generations. Reduced fitness under combined warming and acidification was recovered rapidly, but incompletely, due to interactions between warming and acidification effects.

The nationwide cost of cutting emissions can be affected by local policies. This study considers the differences across the US states, with integrated assessment model results showing that varying state policies only increases nationwide costs by about 10%.

Climate services aim to make climate data and information accessible for climate-sensitive decision-making. However, the grounding of climate services in the norms and institutions of climate science creates tensions that reduce the impact of climate services.

Phylogenetic data over the past ~150 million years show smaller fish occurred in warmer waters, moved shorter distances at low speed and had low speciation rates. Fish moved faster and evolved quicker under periods of rapid change, with implications for movement and survival under climate change.

Climate change may result in larger releases of CH₄ than CO₂ from wetlands as CH₄ emissions seem to be more sensitive to temperature. Globally, CO₂ and CH₄ emissions show a similar temperature dependence but this is modulated by wetland water table depth, which affects CH₄ (but not CO₂) emissions.

The Atlantic Meridional Overturning Circulation (AMOC) is currently strong, but transition to its weak mode could see significant changes in the climate system. This work presents an observation-based early-warning system for such transitions and shows that the AMOC may be approaching a transition.

The authors model the impact of future temperature changes on infection risk for 12 major crops from 80 fungal and oomycete plant pathogens. They find increased risk, as well as crop yield, at higher latitudes and predict major shifts in pathogen assemblages in the United States, Europe and China.