Letters

The stability of climatic conditions since the Last Glacial Maximum has contributed to current global patterns of species richness. Changes in patterns of climate stability this century reveal areas where climate change could reduce biodiversity, with largest losses in past climatic safe havens.

Ozone forms in the atmosphere when other anthropogenically emitted gases react with sunlight and negatively impacts terrestrial gross primary productivity (GPP). Reducing emissions of ozone precursors by 50%, particularly in the road transportation and energy sectors, could increase GPP by 750 TgC yr^–1.

The rapid growth of climate change research presents challenges for IPCC assessments and their stated aim of being comprehensive, objective and transparent. Here the authors use topic modelling to map the climate change literature, and assess how well it is represented in IPCC reports.

Crustose coralline algae help build coral reef structures through calcification, a process threatened under ocean acidification. Juvenile algae were highly sensitive on initial exposure to ocean acidification, but continued exposure over six generations showed a gain of tolerance.

Arctic warming is attributed to GHGs and feedbacks, but the specific contribution of ozone-depleting substances (ODS)—also potent GHGs—has never been quantified. Here, model simulations suggest ODS contributed 0.8°C of Arctic warming and led to considerable sea-ice loss during the period 1955–2005. [This summary has been amended to reflect the addendum published 28 January 2020]

The relative roles of local and remote processes in determining equatorial warming are still debated. Model simulations show that coupled feedbacks strongly damp the equatorial surface temperature response to local equatorial forcing, while amplifying the response to remote off-equatorial forcing.

Detection and attribution typically aims to find long-term climate signals in internal, often short-term variability. Here, common methods are extended to high-frequency temperature and humidity data, detecting instantaneous, global-scale climate change since 1999 for any year and 2012 for any day.

N₂O emissions from rivers have increased globally by a factor of four between 1900 and 2016, with emissions starting to decline since the early 2000s. Most riverine N₂O emissions come from smaller streams, driven primarily by the use of nitrogen fertilizers in agriculture.

It has been assumed that spatial patterns of warming are the same under transient and equilibrium scenarios. Analysis of a multi-model ensemble shows that this is not the case, with greater land warming for a transient state, increasing risks that need to be considered in adaptation planning.

Climate change affects the timing of bird migration, which can lead to mismatch with resource availability. Migration occurred earlier in spring and autumn in the United States during the past 24 years; warming led to later arrival in the western Unites States and earlier arrival in the rest of the country.

The Pacific Decadal Oscillation (PDO), a natural climate cycle, alters global climate and influences ecosystems as it varies between positive and negative phases. PDO predictability is reduced under warming as intensified ocean stratification shortens its lifespan and curtails its amplitude.

The risk of concurrent climate extremes affecting breadbasket regions is increasing with climate change, with wheat, maize and soybean crops at risk of simultaneous failure. Correlation between the regions and climate extremes should be considered to ensure food security in the future.

A large-scale meandering in the jet stream can cause simultaneous heat extremes in distant regions. When Rossby waves with wavenumbers 5 and 7 dominate circulation, there is an increased risk of heat extremes across major food-producing regions, raising the potential of multiple crop failures.

Terrestrial primary productivity will increase with CO₂ fertilization, but water limitation will decrease this positive effect. Analyses of Earth system model projections show that extreme droughts will have a much stronger impact on future productivity than mild and moderate droughts.

The ways in which ocean communities respond to warming are related to their composition. The variety of thermal affinities and thermal ranges of individual species, along with vertical temperature gradients, shape community response and allow the prediction of regional responses to warming.

Increased hybridization has the potential to threaten species diversity. Here population genetic computer simulations show that climate-induced adaptive introgression could readily lead to hybridization even when reproductive isolation is independent from climate.

Opinions on climate policy in the United States are politically polarized. Here, survey research shows that opinion polarization on the Green New Deal developed rapidly due to decreasing support among Republicans, which was associated with exposure to conservative media and increasing familiarity with the policy.

Natural peatlands accumulate carbon but land-use change and drainage leads to emission of GHGs from peatlands. Loss of natural peatland area globally has shifted the peatland biome from a sink to a source of carbon, but restoration of drained peatlands could make them carbon neutral.

Nitrous oxide, a strong GHG, is produced during nitrification. Changes in ocean pH cause its production to increase, relative to nitrification rates, suggesting large potential increases in the future as ocean acidification continues.

Permafrost thaw due to rising temperatures will impact soil hydrology in the Arctic. Abrupt changes in soil moisture and land–atmosphere processes may alter the bearing capacity of soil and increase susceptibility to wildfires, with consequences for adapting engineering systems in the region.