Research articles

Evaluation of climate adaptation policies typically compares differences between scenarios with different levels of, or without, climate change. Many policies, however, address development simultaneously, and focusing only on climate change impacts may not identify the best outcome.

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.

Growth in CO₂ emissions has slowed since the Paris Agreement 5 years ago. The COVID-19 pandemic has caused a drop in emissions of about 7% in 2020 relative to 2019, but strong policy is needed to address underlying drivers and to sustain a decline in global emissions beyond the current crisis.

Analysis of 1,550 future energy scenarios finds that uncertainty in solar photovoltaic (PV) uptake is mainly driven by institutional differences in designing and modelling these scenarios, rather than PV cost assumptions. This suggests more organizational diversity is needed in IPCC scenario design.

Warming causes mountain snowpack to melt earlier during local spring. An idealized model suggests that melt date sensitivity to warming depends largely on mean temperature and its seasonal cycle; the largest sensitivities are seen in coastal regions, the Arctic, western United States, Central Europe and South America.

The authors examine the effect of long-term experimental warming on the complexity and stability of molecular ecological networks in grassland soil microbial communities. They find warming increases network complexity, which is strongly correlated with network stability.

The response of low clouds to warming is uncertain among climate models and dominates spread in their projections. Satellite estimates of tropical cumulus and stratocumulus cloud feedbacks, derived using surface warming trends, suggest a more moderate climate sensitivity than many models predict.

The societal response to the pandemic has reduced global power demand, disproportionally affecting coal power generation and thus leading to a strong CO₂ emissions decline. Policy should apply 2020’s lessons to ensure that power sector emissions have peaked in 2018 and go into structural decline.

Warming is shifting temperate zones to become more tropical. Natural warming and CO₂ vent sites show that acidification buffers warming effects, reducing sea urchin numbers and grazing, thus creating a turf-dominated temperate habitat that is less hospitable to tropical fish than urchin barrens.

Increases in daily temperature variability could reduce economic growth. Analysis of 40 years of subnational economic data and daily temperature observations from across the world shows that higher temperature variability reduces annual income, with greatest vulnerability in low-latitude regions.

The authors use systematic monitoring across the former USSR to investigate phenological changes across taxa. The long-term mean temperature of a site emerged as a strong predictor of phenological change, with further imprints of trophic level, event timing, site, year and biotic interactions.

Climate policy calls for energy demand reduction on top of decarbonizing energy generation. Analysis of historical energy–income data shows that achieving these climate targets alongside economic development poses unresolved policy and modelling challenges, especially for developing countries.